Archive: from the old newbie guide.

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9. The Concept of Perspective


9.1 What perspective is about?

Perspective is often used in non-photographic terminologies, but the application in photography requires a slightly more concrete conceptualisation in order to create or alter it, and as such to inject depth into our composition.

Perspective is about the visual recognisation of all three dimensional relationship of the frame contents, especially that of the subject of interest, relative to each other in the frame and, as a result, to the viewer's viewpoint, derived from a 2 dimensional representation on a flat medium. This basically means that from the viewer's eye on the photograph, he can feel how far, how big, how crowded, how sparse, how mysterious, how open, how dynamic, how stable the situation is.

It probably first comes to the painter when they will noticed themselves drawing the same thing in different 2-dimensional sizes on the painting, in a situation of different spatial representations of the objects. In photography, we can't achieve it by freehand decision, not unless you are a master in graphical manipulation that can create anything.

Perspective defines certain features that allows the viewer to determine the spatial relationship of objects. It is the visual component. In real-life, there are other components such as hearing, movement (e.g. by swinging you hand up and not hitting anything, you will know the roof is at least how high) and touch (mostly by hands with small objects).

There are 3 factors in perspective,
1. correlation to recognisable sizes
2. linear inter-subject distance of depth (most often used as the definition)
3. multidirectional photographer-frame distances (i.e. vantage point)

Quoted from Eugene Ilchenko from photoinf

Perspective refers to the relationship of imaged objects in a photograph. This includes their relative positions and sizes and the space between them. In other words, perspective in the composition of a photograph is the way real three-dimensional objects are pictured in a photograph that has a two-dimensional plane. In photography, perspective is another illusion you use to produce photographs of quality composition. When you are making pictures, the camera always creates perspective. Because a camera automatically produces perspective, many novice photographers believe there is no need to know much about it. This attitude is far from correct. When you know the principles of perspective and skillfully apply them, the photographs you produce show a good rendition of the subject's form and shape, and the viewer is given the sensation of volume, space, depth, and distance. Additionally, the photographer can manipulate perspective to change the illusion of space and distance by either expanding or compressing these factors, therefore providing a sense of scale within the picture.

9.2 Perspective: Correlation to recognisable sizes

Most people can easily just think of perspective as a plain science of lines and forms, but it is something more than that. It also involves having recognisable objects that we can correlate to its usual size. The interesting ambiguity of it all is that it serves both as a purpose of representing what we recognise as well as to create illusions.

We recognise an apple as an apple, becos we see colors - it is red, becos we see tonal differences and direction of light - it is spherical, becos we see details, texture and form - it is smooth with some markings on it, it is round, and last of all, if there is something else that looks exactly the same except for size, we know it is an apple when we have a picture that shows it being held in a hand.

It is from recognisable sizes of recognisable objects that we expand and inter-relate the physical sizes and distances of other objects simply by how they look on a 2-dimensional view.



9.3 Perspective: Near and far relationship to subject of interest

Here, it is the same as the above factor of linear inter-subject distance of depth. We are now talking about something usually in the main central portion of the frame instead of the peripheries, the subject of interest which is usually within the thirds or in the centre. Depth is most noticeable in this region, related by a linear relationship of how far and how near the subject is to you, in terms of eye level horizontal distance.

This is first of all described as something near to you is bigger and something further is smaller, like a road, which eventually converges at the horizon into a vanishing point. Hence everything on this linear depth will have change of sizes (magnification) apparent to your viewing depending on how far they are from you. Perspective will describe on how fast they shrunk in size with distance from you, which hence determines how much they shrunk in size from another subject that is in front of them, giving a sense of differential distance.

We will often see the example of how focal length compresses or spaces out the items immediately in front of or behind of the subject of interest, to suggest what perspective is. This is often quoted as the definition of perspective, also as described in wikipedia, which refers to "the way in which objects appear to the eye based on their spatial attributes, or their dimensions and the position of the eye relative to the objects."

The rule is that with shorter focal length in wide angles, items appear spaced out from each other whereas with longer focal length in telephoto angles, items appear compressed together. Photographic uses are usually secondary. In taking landscape of very faraway slopes, using a telephoto will help isolate and put different components, such as houses, together with compression. In taking portraits, the use of perspective need to be closer to what our eyes see and requires focal length that gives similar angle of view (as described in following chapters), if not they may appear too widened or compressed, thus distorted. Such distortion is often acceptable for events, but generally not for group photos or portraits.

A simple google is going to give many pictorial descriptions. I learnt mine from books i read earlier on. Online examples include some compositional factors described by Klaus Schroiff's photoinf, which also illustrate the above point under "Linear Perspective". "Rectilinear Perspective" is also described within but more of a concerned in distortion in wide angles and deliberate composition in fisheye photography.

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9. The Concept of Perspective


9.4 Angle of view and perspective.

Perspective is governed by 3 factors,
1. actual distance of the sensor (i.e. camera body) to the subject of interest.
2. vertical height differences of the sensor versus subject of interest, relative to ground
3. angle of view from the focal length and sensor size.

In short, it depends on where you stand and the focal length you have.



9.5 Distortion in wide angle

The angle of view in photography is variable unlike how we see with our eyes. As such with a narrower angle, items looks bigger and narrower, more similar in relative size and hence looks nearer to each other, i.e. compressed perspective. Likewise with a wider angle, items looks smaller and broader, more varied in relative size and hence looks farther from each other.

The more the angle of view differs from our natural vision, the more distorted they look on the picture. The more we are used to seeing something in our natural perspective, the more we will find it weird to see it distorted. that is why we prefer seeing our human faces in the angle of view and perspective closer to our vision, less so with faces of animals and even less so for inanimate subjects, and especially less so for large tall buildings with which even with our vision, we see it in various forms depending on how far and at which level we see it, hence distortion is widely acceptable.

Distortion of faces are most particular in the periphery of very wide angles, especially when the wide angle application is not just from left to right but also vertically from a very low or very high angle. It is also not suitable for shooting of contemporary group photos of people who expect to see their faces nice on your photo.

Example of distortion of faces. Note those at the sides.

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Controls on the camera body


1. Focus
1.1 AF frames in viewfinder
1.2 AF autonavigation
1.3 AF drive
1.4 Focus indicator in viewfinder
1.5 Shutter release button's half-lock focusing
1.6 Focus lock
1.7 AF beep
1.8 AF assist illumination
1.9 AF/MF button on body and lens

2. Exposure
1.1 Exposure modes
1.2 Exposure & general purpose dials
1.3 ISO
1.4 Metering modes
1.5 EV interval and control
1.6 EV indicator
1.7 Bracketing
1.8 Exposure lock

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Composition: Spatial relationship of a 3D vision


The next crucial step in understanding creative photography with alteration of settings, is to understand the spatial relationship inter-relates with exposure, focusing and motion, with resultant composition and sharpness.

rewriting: new.....
2. The Concept of Lens and Focus
2.1 A point to point diagram
2.2 A simple lens setup
2.3 A two/multiple lens setup
2.4 Focal length and its definition


old parts
1. The spatial relationship and its hour glass diagram
1.1 Photography is within a frame: Field of view
1.2 The angle of view is between the field of view and from where you are standing
1.3 The hour glass shaped diagram
1.4 Optical centre
1.5 Angle of view represented on the sensor

2. Focal length
2.1 Focal length: how wide is your angle of view
2.2 What does focal length affects?
2.3 Range of focal length and their angle of view
2.4 Zoom in focal length
2.5 Required focal length for composition - your primary lens concern.
2.6 On focal length: A camera's vision against our eyes.

3. Integration of spatial concept
3.1 The bottom of the hour glass: Focal length, sensor size and angle of view
3.2 Focal length conversion factor
3.3 Change of camera body with same set of lens
3.4 Zoom: Focal length versus angle of view

4. Spatial rules reiterated
4.1 Rule 2: Perspective follows the angle of view
4.2 Rule 1: Sensor size & focal length affects the angle of view
4.3 Rule 3: Lens-optical-centre-to-subject distance and focal length affects the size of subject

5. Size and Magnification
5.1 Size and composition

6. Perspective
6.4 Other things that changes with distance.
6.5 Perspective: Vantage point
6.9 Panaroma

7. The 3rd dimension
7.1 Elements of the 3rd dimension - perspective, shadows, depth and scale of comparison
7.2 Presence of size/distance perspective: Differential size of identifiable object
7.3 Scale of comparison
7.4 Exaggeration of near and far subjects
7.5 Leading lines
7.6 Implication of movement direction and active space
7.7 Highlight, shadows and contours
7.8 Presence of washing out in haze as distance perspective
7.9 Depth of field in the 3rd dimension

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2. The Concept of Lens and Focus


2.2 A simple lens setup

The above diagram is exactly a simple lens setup.

This is just like our eyes with a lens in each eye. Unlike a pinhole camera, a camera with lens makes use of the ability of the lens to converge and diverge light, thereby giving the ability of giving sharpness over an area of large aperture.

A point source of light, for example, the centre of the candle light, will dissipate in all direction, illuminating the whole place and only dropping in intensity as the distance and spherical area enlarged. Without a lens, the different directional emission of the point source will fall over the entire area of the sensor on all the data points, and likewise, the different directional emission of another point source will also fall over the entire sensor. In the end, nothing can be sharp.

Basically, lens works by having the sensor at a certain distance S1 from the lens, and on the other side of the lens at a certain distance S2 from that lens. The single point source of light will as usual give off light in all directions, but no matter what direction the light is emitted, as long as they enter the lens at any part of the lens, they will turn at various angle, and converge on leaving the lens, eventually all the different divergent light will converge back on a single point. Similarly any other point source of light in the same spherical distance S1 from the lens, will diverge in all directions, enter the lens at any point, and all diverge at a single point in the same spherical distance S2 from the lens. And the two point source at distance S1 from the lens are separated the same as much as they are separated at distance S2 from the lens. This is the basis of image sharpness with a discrete unmixed point to point duplication, via convergence of the divergent emission, provided that the distances S1 and S2 are maintained.

The points that are farther away from S1 distance will also converge but will not converge into a single point at S2. A point that is before S1, will converge before S2 and diverges again as a small circle of field. A point that is behind S1, will converge beyond S2, and is not fully converged at S2, still remaining as a small circle of field. That is basically the cause of out of focus, which may appear as different bokeh (blurring characteristics) depending on the diaphragm blades. A further concept from this will be depth of field, discussed at another point of time.

The relationship of how distance S1 and S2 varies with each other is dependent on the curvature of the lens and its converging power on each side. Our eyes demonstrate flexibility in the lens morphology, and although the distance of the retina and the lens will not change a lot, the change in the lens curvature makes it possible to focus at very near and very far distances, i.e. variable S2. That is what makes our eyes different from a camera's single glass lens element, and the need for the multiple lens element to change the characteristic of the whole lens unit, so that even at a single focal length S1, the focus can be applied at nearer subject and further subject, with different S2 distances.

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What is within this frame is called the field of view. Whatever you capture within the frame is within this field of view.

If we shoot an extreme fisheye, or attach a lens of smaller image circle onto a larger sensor, the corners of the picture will be black.

Framing depends on 3 factors
1. Where you are standing and where you point towards.
2. The focal length as determined by the object distance u and image distance v.
3. The aspect ratio of your sensor.



1.2 The angle of view is between the field of view and from where you are standing

Wikipedia

With an overall generalisation, between what you see within the frame and where you are standing forms the angle of view. This concept of the angle of view forms the initiation of the spatial relationship in the picture to your shooting habits. What immediately determines your field of view would be the distance from where you are standing and the properties of the lens, which would be described below.

It looks like the field of view and the angle of view sounds pretty the same, but it is not. angle of view is a constant for a particular focal length, regardless of the sensor size and regardless of distance from a particular subject. Field of view is however the combination of the effect of the angle of view and the distance of the subject from the pivot (the optical centre).



1.3 The hour glass shaped 2D diagram

I named it on my own as an hour glass shaped diagram. This is the main 2D diagram I used to visualised how a physical spatial relationship of objects go through a photographic transposition onto the picture we see on the sensor. It should be similar to a typical pinhole camera diagram that shows how a upright tree gives an inverted image in the black box, although in this case there is a lens which gives a certain unique property known as the focal length.

Look at the diagram at dpreview, (link to picture alone), as well as above.

At the neck or pivot of this hour glass, the angle that opens it up forward towards the scene and backward towards the sensor is the same - that is the angle of view, which correspond to the field of view that frame off a certain portion of the scene (where you see more of it than the camera) to be projected onto the sensor.

There are corresponding values on each side of this angle, i.e. both side of the hour glass. On the sensor side, there will be an image distance, and on the frame and field of view side, there will be the object distance (I will edit the picture in the near future) which we will discussed later.

Note that the neck of the hour glass correspond to the optical centre, with the angle of view adjacent to it. The image, e.g.billboard, that fills up the picture on the sensor from the left to the right will have a certain distance from the optical centre, any shorter than that, only part of the billboard can be captured, and any longer than that, the whole billboard will be included in a larger field of view, and gradually becoming smaller and smaller as the distance increases.



1.4 The optical centre

Being weak in physics, I reckon somewhere i may be wrong and misleading. For simplified understanding for myself, I derived my own hour glass diagram as above, and the optical centre is simply to demarcate a part of the diagram. It aids in the understanding of the other parameters which are more important but it itself is not of a practical concern when it comes to shooting (at least before i get further enlightenment). The real physics of the groups of lens would probably be much much more complicated.

From the Cassell's Cyclopaedia of Photography quotes as follow. The olive green small print is my addition. The black standard print is from the quoted source.

1. "the optical centre is the point at which rays passing through a lens cross each other"
(which is simplified in my diagram as the left and right most point of the picture).

2. "It is only in the case of a symmetrical lens that the mechanical and optical centres coincide."
(and in almost all our lens design, they are at least a combination of a few elements, which thus would not be the case of a symmetrical lens where the physical centre becomes the optical centre. A comparison can be made with for example the centre of gravity of objects. Only in a ball or cube or evenly faceted object with uniform mass distribution would the physical centre be the centre of gravity. The lens in photography are sophisticated pieces that have movements within that changes the optical centre to suit what you are shooting.)

3. "According to the form of the lens and the position in which it is placed, the optical centre may be within the lens, or considerably before or behind it."
(This shows that the optical centre is more of a concept to grasp, rather than a physical point that must be within the lens. As much as you need to know, it can be anywhere, and just served to explain the concept of the angle of view, field of view and focal length)

4. "It is often stated that the focal length of a lens should be measured from its optical centre, but this is not correct; the point measured from should be the node of emission"
(I dun quite understand this..... but i think we can leave it aside for the moment. )

Anyone stronger in physics and keen to understand more can read more over here. As for me, I'm frozen.

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1. The spatial relationship and its hour glass diagram


1.5 Angle of view represented on the sensor

This is the diagram i also show on the digital aspects on the sensor. It shows that at the same focal length of 26mm, the full frame 35mm-film-size sensor gives a diagonal angle of view of 80 degrees, whereas a 4/3 system (17.3x13mm) which approximates to 18x12mm with half the diagonal length of the 35mm-film-size, will give a diagonal angle of view of 45 degrees.

Basically there is just about two things.

1. What falls on the sensor is an mirror image. The point on the frame's left falls on the right, the right on the left, the bottom on the top, the top on the bottom. Does it matters? Yes and no. Why no? You still see the correctly orientated view in your optical viewfinder, the display and the computer file. Why yes? When you see the dirt on your top left hand corner, it is on the bottom right of the sensor physically, but then you will always see it - if you dun see it on the sensor, you probably can't clean it too by yourself with a simple blower.

2. If you have noticed when i draw the simplified hour glass, it is a plain 2D diagram of a single plane, more easily understood to be the horizontal or axial plane where we look from left to right of a scene. But when we do figures to really compare different sensors of different aspect ratios and in respect to image circles, it have to be standardised to the diagonals as shown in the above diagram and as explained in F1.5 Concept of diagonal measurement of the rectangular sensor, as well as in dpreview. That derives the true angle of view or picture angle.

3. The same angle of view would be maintained by congruent change of focal length and sensor size.

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2. Focal length


2.1 Focal length: how wide is your angle of view

Quoted from a Nikonians article by J. Ramón Palacios, focal length is the distance between the lens node of emission to the plane at which objects at infinity are brought into focus to form a sharp image; i.e. at the film or sensor plane in a camera, as in this diagram from the page.

When the focal range of the lens increases, the physical length of the lens also increases to pull the optical centre further away from the sensor.

It is shown on the hour glass diagram above on what it means between the sensor and the optical centre. And in photographic purposes, the sensor size and the focal length determines the angle of view and hence the field of view. In short, it means how wide you see.

I did some arbitrary diagrams here to give a simple pictorial view of how focal length affects the angle of view and resultant field of view, expressed as the number of people you can include in the picture, supposedly if the distance between you and the people are the same, i.e. nothing moves.

The same idea is also shown in this diagram and the easy to understand website.

this is 20mm focal length on Nikon D50, which corrected by sensor size is equivalence of 30mm on a 35mm film camera. i'm standing about 10m from the nearest subject, but becos of the wide angle, they look further as they are smaller.

this is 170mm focal length on Nikon D50, which corrected by sensor size is equivalence of 255mm on a 35mm film camera. i'm standing about 3-5m from the monkey, otherwise could be dangerous for myself. a long focal length is required for close-up from a semi distance or whole body from a long distance.

A demonstration of full frame field of view is given for 8mm, 16mm, 20mm, 24mm, 28mm, 35mm, 50mm, 70mm, 105mm, 135mm, 200mm, 300mm, 600mm, 1200mm by Tom Davis.



2.2 What does focal length affects?

Focal length affects a few things
1. angle of view and framing
2. resultant spatial relationship of the perspectives
3. degree of magnification
4. depth of field


The focal length is invariably and directly related to the angle of view by a mathethical relationship without other variables. This is demonstrated with a diagram from cambridge in color (link to picture alone). This relationship is inverse, the shorter the focal length, the wider the angle of view, and the longer the focal length, the narrower the angle of view. Hence, short focal length lens are called wide angle lens while conversely, long focal length lens is called telephoto lens not by its angle but due to its distant framing and magnification. Also shorter focal length have a wider depth of field that lends sharpness to a landscape picture whereas longer focal length have a narrow depth of field that gives good bokeh background for a wildlife shot but may be too narrow to combat with in a macro shot.

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2. Focal length


2.3 Range of focal length and their angle of view

The description of which what falls into which category is not universally defined, or perhaps not with any standard guidelines. And focal range can overlap here and there. To just give a general idea by my own perception, which by no means is accurate, just personal and arbitrary, the effects of lens focal length on a typical DSLR with 1.5x conversion factor.

Focal length range of a lens is given without regards to the sensor size of the camera body, hence the eventual suitability of the lens to shoot a particular subject of a certain size or from a certain distance, is dependent on the sensor size and hence its conversion factor.



2.4 Zoom in focal length

Zoom range in DSLR is given in specific range of minimum to maximum focal range, but other terms are more often given for prosumers and compacts. Optical zoom refers to the number of times the minimum focal length can be multiplied by till the maximum focal length. Hence a 10-20mm lens have an optical zoom of 2x, while a 18-200mm lens have an optical zoom of close to 21x. Digital zoom is not a term that DSLR users is that familiar with, but it refers similar to cropping in post-processing. While optical zooming results in a change of focal length and a change in perspective with the same amount of pixels , digital zooming has no change of focal length and no change of perspective with decreased amount of pixels.

This is a good read from dpreview on optical zoom and digital zoom.



2.5 Required focal length for composition - your primary lens concern

With a knowledge of the camera and sensor type/size/conversion factor, the physical distance of the subject from you and the physical width of the background you want to cover in your horizontal frame, the required focal length to fit that composition you want, can be calculated online from this website's "Required Focal Length Calculator". Take for example, there is a person standing 100m from you, standing at the door of the house, and you wanted to catch the entire breath of the house which is 10m wide without including the ugly pots of plants just next to the corners, and you are using a Nikon D50 whose conversion factor is 1.5, key in the values of 100, 10, DSLR with CF of 1.5, I would get a focal length of 239mm. Which means that with a Nikkor 18-200mm lens that i have, the longest focal length i have, i cannot zoom in tight enough and my framing will include the entire width of the house but i wound not be able to exclude the plants at the side. In order to fill up the frame exactly the way i want, and not having 239mm focal length available, I can only walk in front 16.5m till I'm about 83.5m in front of the person, to use the focal length of the lens at 200mm.

The focal length hence relates to the how the physical size of the subject and background fits onto the physical size of the sensor, with relation to the physical distance.

Of cos, only the sensor size is really a non variable with that one camera body you are using. The amount of background, and the size of the subject you want to capture either as a small area in your picture or to fill up the whole picture is variable. If the desired framing is decided however, the physical size of the subject and background fitting onto the physical size of the sensor becomes a non-variable, i.e. a fixed composition, then what determines it will become a function just between the physical distance and the focal length.



2.6 On focal length: A camera's vision against our eyes.

It is commonly said that our eyes have a focal length of 40-60mm and hence an arbitrary focal length of an easily made 50mm prime lens becomes the standard. Looking back at the definition, the focal length should have been referring to the retina (sensor) and the lens, and that wouldn't be 4cm to 6cm isn't it? Our eyes can't be that big.

Also I checked with my 50mm lens which sees significantly different between popping my eye over and away from the viewfinder, and always thought that it is the 1.5x conversion factor that gives a different view, as the focal length is now 75mm.

The answer is the focal length of our eyes is actually 17mm. Refer here for more information. However we can also accomodate our eyes to see at a slightly shorter focal length of 15.9cm. But then why is the focal length of 43mm (or 1.5x of 29mm) a quoted focal length of for vision.

A discussion over the nikon forum cleared my doubts, because although our eyes have a focal length of 16-17mm and a view that covers almost 180 degrees, we only pay attention to a mental image of 45 degrees. So if we use a calculator from this imaginatorium or tawbawaree, without a conversion factor of a smaller digital sensor, a 50mm lens on a 35mm format, giving a width of 36mm, a height of 24mm, a diagonal distance of 43.2mm, we'll have 46 degrees angle of view based on that diagonal distance which is the widest length of the 35mm format. This relationship is further discussed by Daniel Rutter.

However, when I use my Nikon D50 with a specification of sensor size given as 23.7mm x 15.6mm, and putting in a 50mm prime lens focal length into imaginatorium, i derive an angle of view of 31° 41' which is the same as 76.25mm in a 35mm-film-size sensor. The focal length conversion factor should then be 1.525 which is approximately 1.5 as people usually use.

To approximate a standard view

Hence, a standard lens of 50mm will only approximate our vision if used on a full size sensor and a wider lens of approximately 35mm would be more suitable on a modern DSLR with a conversion factor of about 1.5.

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3. Integration of spatial concept


3.1 The bottom of the hour glass: Focal length, sensor size and angle of view

Looking at the hour glass, the bottom shows that the focal length correlates to the sensor size at the same angle of view.

Three concepts to grab.
1. Focal length conversion factor (maintanence of angle of view)
2. Change of camera body with same set of lens (varying angle of view)
3. Zoom: Focal length versus angle of view (varying angle of view)

If the angle of view remained constant, the focal length lengthens as the sensor size increases. This forms the basis of conversion of most digital sensors into equivalents of the 35mm film format. With the same angle of view, the perspective of the contents within the frame remains the same, hence the composition; which means that near subject and far subject looks the same distance from each other in both pictures. The inter-relationship is formed by the focal length conversion factor.

The angle of view changes if the change of the focal length and the sensor size is not changing at the same magnitude, which means that if the focal length or the sensor size change while the other remained the same.

In a practical situation, it is usually the focal length that changes in the lens focal length setting, while the sensor size will be the same in your camera body; we only talk about different sensor size in different bodies to illustrate the required focal length conversion factor to achieve comparable angle of view and perspective. However, this concept might come in with the change of a camera body of different sensor size, using the same lens.

On the other hand, changes of focal length is done all the time when using different lens with different focal length range and when using different focal length in the same zoom lens. The focal length changes the angle of view in a reciprocal manner. The shorter the focal length, the wider the angle of view; the longer the focal length, the narrower the angle of view.

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5. Size and Magnification


5.1 Size and composition

Size of subject is an obvious photographic element that is sometimes not so obvious to new photographers but that is actually the immediate impact of focal length, which will be eventually described subsequently. It is also a compositional element. It decides on your choice of subject, directs your approach and affects your choice of equipment.

Take for example, your wife is your subject. It can be a macro take of her eye, where all the reflection on the cornea can be seen. It can be a tight shot of part of her face from forehead to below the nose. It can be from forehead to chin. It can be the head and the shoulders with some space around the head. It can be the upper part of the body. It can be the whole body filling the frame. It can be reasonable filling of the whole person within a horizontal framing. It can be half the height of the horizontal framing. Or it can be just a small area like a 20cents coin on an A4 paper.

This shows that there is so many way of doing things, and each of them can derive different results, some of which works and some don't, all depending on what you make out of each case. Nevertheless all of the above shows the difference in the size of the subject, which actually is the one of the most obvious thing in composition.

I have been thinking about how size impacts our composition. I find that it is probably difficult to describe it comprehensively and cannot find good resources for such purposes, as there are immersely more "how to" description online rather than "why". Afterall, it is an art because it is so hard to make things work like science, although i'm pretty sure there is always something behind each situation.

I derived my own thoughts on this issue. One of the way it can be decided by is the amount of details that can be reasonable appreciated. Take for example, a solid silhouette against a bright background can work like magic even if it occupies a very small area of the photograph, provided that the composition is simple enough to accentuate that small area of interest. But in order to appreciate the expression of a face, a head and shoulder shot perhaps is the minimal before the face becomes large enough to be seen clearly, and of cos a tight shot of the face from forehead to chin will throw the heaviest impact. On the contrary, as the face gets bigger and bigger, the background will receive less and less space, and so depending on how much each of them, the subject and the background, requires in terms of size and space, to show what they are capable of, that determines the art of deciding on the size.

Take for example, the above shot showing the size of a tiny silhouette of my friend who is taking a shot of his scene with his compact. However the size is merely enough to show the presence of a person but not the action he is doing. It is too small. In fact, it couldn't be certain that it is a person and something that stands upright out if the subject is not described in words. In order to see that it is a person, it got to be larger like below after cropping.

And even so, it couldn't be sure that what is he holding in his hand. So it needs to be larger and I crop further.

Unfortunately, by right at this size, we should be able to see what is he holding in his hand, but that is beyond the resolution and depth of field allowable for the shot. If the desired take is to be able to show what he is doing, there is a need to take it at such magnification at the original resolution. Cropping and enlarging is not the solution, as shown above.


Another concern is a geometrical concern. The way each subject is portrayed in terms of size, also determines the margins and how it cut across the frame. If taken in a large enough size, it can divide the picture into different spaces, whereas if small, it gets enveloped by negative space around. When important structures such the eyes are placed near the edge, it adds tension and brings out the emotions of the face. When the whole face gets enveloped by surrounding space, it shows more harmony in relation to the background. The size of the main subject may also be involved in balance, which is a more complex relationship that involves size, tones, details and colors, typically in a dynamic balance where a big size lighter-toned and less detailed subject will balance with a small size darker-toned but more detailed subject.

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6. Perspective


6.4 Other things that changes with distance

Other than size perspective, things that changes with distance giving a sense of depth includes
1. the degree of off-focus - under concept of focusing: depth of field
2. washing out of colors in hazy situation, with increasing depth, there is a thicker layer of haze between the subject and the viewer, in particular to layering of mountains in landscape shots.



6.5 Perspective: Vantage point

So far we have been talking about only 1 linear aspect, near-far relationship, but vantage point is about all 3 dimensions, depending on where and how you see a subject relative to horizon. Normally we shoot at normal eye level at standing position, anything that is different from usual is considered a choice of vantage point.

Vantage point will tell the viewer how you are viewing a certain subjects from the distorted perspective, which can draw emphasis to a certain area of a picture that is normally not paid attention to.

Low vantage point aka low angle shot:
simulates the vantage point of those people who is squatting low and places emphasis to the bare foot.

Usually for the use of high/low vantage points, the emphasis will still remained on the face as it is natural to zoom our eyes into the area of unique identity. However, it is better suited for fun pics and children, as adult females usually do not like to see distortion and over-emphasis of their chin or their forehead, also it is the easiest to vary our vantage point against children, whereas it is difficult to do a high vantage point for an adult from close distance.

Another low vantage shot, of kids.

Nuts have a good thread to show how people find their vantage points, to the point of using a ladder. See this sakura fever.

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6.9 Panaroma

Panaroma is an aspect ratio concept, as well as a concept of angle of view. Conventionally taken, a photograph with a wide take spanning an aspect ratio of 2:1 or more is considered a panaroma. More in wikipedia and panoguide says more about aspect ratios pertaining to panaroma.

For a simple 2:1 panaroma, one can simply crop off the top and the bottom to give the aspect ratio, but that means information taken on part of the sensor are all discarded, resulting in a decrease in the sensor size being used and a smaller output size and when increased in output size simply reduces the resolution. Hence the idea of stitching different pictures to form a larger picture comes into concept and there is many programs used for that purpose. Stitching requires overlapping takes to ensure seamless stitching.

However in view of peripheral distortion of each picture, there would be problems in stitching up nicely and there are special control equipments meant for stabilising a smooth transition and ensuring a single axis of rotation.

This field is quite specialised. For further inspiration, one can view from this website by Hans Nyberg.

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7. The 3rd dimension


7.1 Elements of the 3rd dimension - perspective, shadows, depth and scale of comparison

A picture is a 2-dimensional representation of a 3 dimensional relationship. What you have is a width x a height that makes up your 2D picture, and whatever contents it has gives the 3rd dimension, its depth, via differential scale and sharpness from subjects nearer to you and far from you.

As said, depth is the 3rd dimension to a 2D picture. It is something that helps you see the picture and relate to an actual situation in life. As this topic is relatively complicated for even me myself, i have withheld the entry for a very long time till now. I would broadly categorise them into 4 categories, before i read more and learn more to share.

At this point of time, do not confuse depth and depth of field. Depth is the perception of near and far, and the depth of field is one factor whose variability will affect the perception of depth. Depth is the broader term. Depth of field only refers to the in-focus distance that contribute partially to depth.

What adds depth to a picture?
1. Variable size that tells us there is a difference in two objects spaced apart.
2. Variable sharpness with focused and out of focus areas which also tells us they are spaced apart. This also help us to bringing attention to the subject.
3. Scale of comparison makes use of familiar objects to tell us how big an adjacent structure really looks.
4. Shadows add contours to face and relativity between similarly toned subjects



7.2 Presence of size/distance perspective: Differential size of identifiable object

Perspective refers to the change of relative dimension with distance. This varies with the angle of view, and the relative distance of the object from it.

The same item looks smaller when farther, and looks bigger when nearer. Hence in our standard vision, whatever that seems to be of similar size looks like they are at the same distance from you, and the difference in expected size will help to gauge the distance too, the smaller the farther.

An example of how the human size looks different with a difference of distance.

7.3 Scale of comparison

Sometimes, a familiar object is needed to tell us how big is a less familiar object. For example, a person next to a big tree, can illustrate how tall is the tree. Becos we can see a very big giant cedar tree or a tree-like bonzai, sometimes alone we can't tell the size. but with a human being that is probably about 1-2m tall, we can easily compare them if they are at the same distance from you, i.e. they are next to each other.

For example, this picture of the milky lake at yangminshan, Taiwan, shows that without an object of comparison, you may not be able to tell the size of the lake at a distance. It can resemble a pile of water on the grass patch if you did not pay attention to the texture and size of the surrounding vegetation which is small and difficult to decipher.

The following example shows that with the gate, statues and the monks in saffron adjacent to it, you can see and imagine the dimension of the trees. With the wall itself, they may not be sufficient.

However, variable distance with an angle that our eyes is not used to can derive new refreshing results. The cows are larger than the kids on an apparent view. Supposedly from eye level, we would think it is normal of the cow to look larger becos it is nearer, whereas the kids who is further and positioned above the cow, will look smaller becos it is farther. However, from a low angle, the kids are now positioned under the belly of the cow, giving a transient illusion that lends drama to the picture.

Also, note that the scale of comparison need to be directly adjacent, otherwise if there is a distance between the two, the comparison will become less striking and more difficult to tell. note that the people in the foreground does not tell you very well about the size of the buildings. however, the two human shadows on the platform in the distance does give you a better idea.

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7. The 3rd dimension


7.5 Leading lines

Leading lines is a component that contributes in 2 factors.

1. Just like star constellations, there may be a few subject of interest or volume filling forms which can be link by vague lines leading to a strengthening of composition. These lines often serves as a leading line that lead the eye from one subject to another subject, and often gives a sense of relationship.

2. It is a feature of what we call a vanishing point perspective as described in photoinf. It is based on the property of perspective of size difference with distance, the nearer the larger, the further the smaller, hence converging into the vanishing point at infinity. This often is not a deliberate photographic technique because it will naturally appear when you point to infinity in such a manner, however the thought of looking for strong lines that lead to the vanishing point, their continuity, as well as setting a subject of interest at the vanishing point, will help to make use of this property.

The reason why leading lines contribute to depth

Usually we have a straight horizon - horizontal, as well as buildings - running vertically or close to vertical. These are lines that often sets the skeleton of our vision in telling us where to gauge for balance, what is ground and gravity and what is elevated in front of us. We will become disorientated if we dun see these lines.

On the contrary, lines that runs diagonally, other than implying dynamic viewing angles, also implies a change of position (size) with distance, giving a relationship of perspective as mentioned earlier in 2.3 Perspective: Near and far relationship to subject of interest. It gives us the idea that something is leading inwards to the subject of interest rather than going vertically upwards to the sky.

The example above shows the vanishing point, with curving meanders. However as the perspective shows as a relatively eye level, the depth is not very strong. Also, there is a lack of a focal subject along the vanishing point, which would be suitable along the horizontal stripe of road on the picture's right. Picture is taken at Hap-hoan-soa (hohuan aka hehuan) in Taiwan.

Usually leading lines are described with examples using roads, as above. However, we do not always have roads in our composition, rather most of the leading lines are derived from vague outlines of shapes and forms, which are either real edges or made up by contrasting/differing areas of tones or colors. That takes some imagination, but are probably easier to see than making out shapes of star constellations. And sometimes, there may be more than one focus of interest, often a main subject with multiple other complimentary epicentres in location further away from the main subject. And since these lines are not as concrete as roads, the mind need to be tuned to compositions in terms of forms and shapes, and you may need to make decisions to compositions on spinal reflex.


I picked an example of a picture i like, that shows human flow naturally revolving around the subject of interest. It goes to show that in complicated detailed pictures that seem busy, there are still rules of composition that runs around.

With permission from Leongfm from his thread on East Turkistan, I've chosen this picture. I like this especially for its ability to draw attention to focus of interest in a seemingly busy ground. There is so much going on, but the composition works. There is sufficient depth of field, the exposure is spot on, and it brings out the idea that in many photographs, especially busy one, there is often more than 1 subject of interest, and the main interest point to me is surprising the face on the left. While often we wanted the rule of the third, this one works just right with the face on the far left, showing just enough of the face. I dun mind a bit more space too, but not too much, this one just just al'rite for me. I may like some post processed brightening of the face, but that is of secondary importance, as it has already made impact with the eye contact.

It could be imagined that the outlines of the larger components, the people and the cows, will make some of the outlines which draws interest to a small area in the centre, depicting a deal. Additional outlines are drawn from vague line so human traffic and the horizon. Although most of the lines are drawn towards this deal, the whole picture does not have that much impact if there is no inclusion of the face on the left. This face is large enough to be clearly distinguished from the rest of the picture. It has its own lines leading to it and does not merely floats. The surrounding shapes are largely simple, making the details of the face easier to stand out. And the hand he places on the cow, draws the two focus in continuity.

In addition, the background has a different tone, colors and vertically running lines, and helps to contrast against the busy subjects/foreground.


And a case of weak composition is shown as below,

I'm a bit lazy to draw lines here, but maybe later. As can be seen, there is a loop of people without definite direction, the girl is looking at me but has no leading lines around her. On the top, there are two directions, one geared towards the ticketing site, another towards the gate, both away from each other. Once in a while, you may try to get certain pictures for documentational purposes, and composition is neither given nor made. Give it up or just accept the weak composition as another ordinary photo. The photo above is not that faulted for technical errors, but it just dun work for its non-associative composition.

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7. The 3rd dimension


7.6 Implication of movement direction and active space

In a static picture without long shutter speed and movement trails, the direction of moving subjects are dictated by their perceived front and back along the perceived route. To depict a moving subject moving in, we show the front or side profile of the front of the subject, place the subject's tail near the edge, with active space in front of the subject's front. To depict a moving subject moving away, we show the back or the side profile of the back of the subject, place the subject's tail in the more centre part facing the active space with the front of the subject towards the edge or near and towards the vanishing point.

Similarly, the line of sight of a living creature follows the same rule. Leave an active space in the line of sight. Depending on your focal length and the distance of the item of the subject's sight, you may or may not be able include the item within the active space.

More can be read from digital photography school by Darren Rowse.
Give Your Subject Space to Look Into
Create Active Space In Your Photography
Ignore the ‘Active Space’ Rule for Moving Subjects

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7. The 3rd dimension


7.7 Highlight, shadows and contours

Both highlight and shadows is another way of introducing depth into your picture. It gives you an idea of direction.

Depending on your taste, the direction of light, whether from the sun, through a window or from an ambience light source, can derive different effects. This is more often applied in portrait studio in the concept of using fill in lights, but it can be virtually applied in everything.

Light can be diffuse or directional. To derive more contour, directional light is used, usually with a low angle. The direction of light can be from the front, at an angle (quarter), from the side, top, base. There could be effects derived from knowing the 3D feature of an item, such as the nose in creating butterfly lighting. For wider uses, most of the rounded objects, such as a person's hair on his/her head, produce another avenue of creating what is called rim lighting, which means the an almost back lighting is used with a slight angle, and light spills over the rounded edge to create a margin.

Back quarter lighting on the face, with the face texture shown.

Use of spectacular directional lighting, such as sidelighting, gives you

1. increased contrast between highlight and shadow, and brings you texture and details
2. shows the three dimensional structure of an item with depth
3. can be used to hide unwanted details in the shadow

Kindly approved by zerodivine for posting, one of the best example of rim lighting, at Bashang.

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About lens and filters: The pre-body optic axis


1. DSLR lenses in general
1.1 What lenses is all about.
1.2 Lens is a group of lenses.
1.3 Aperture size: Fast lens
1.4 Focal length: Prime versus zoom
1.5 Focal length: Standard and kits
1.6 Electronic verses Manual: Compatibility issues in control of aperture, focusing and metering


2. DSLR lenses physical features
2.1 Types of connection
2.2 Lens mount
2.3 Lens front thread
2.4 Lens controls
2.5 Lens nomenclature
2.6 Lens abbreviations
2.7 Weight and dimension
2.8 Build of barrel and rings
2.9 Manual focus override


3. DSLR lenses functional features
3.1 General categorisation of lens by focal length
3.2 Minimal focusing distance
3.3 Reproduction ratio
3.4 Maximum aperture
3.5 AF speed
3.6 Optical quality


4. Type of DSLR lenses by focal length
4.1 Fisheye
4.2 Ultrawide angle
4.3 Wide angle
4.4 Standard and Street range
4.5 Telephoto


5. Type of DSLR lenses by special features
5.1 Macro & close focusing
5.2 Close-up filters
5.3 Extension tubes
5.4 Reversing or Inversion rings
5.5 Convertors
5.6 Tilt-shift lens
5.7 Lensbabies


6. Lens quality & deficiency
6.1 Lens review list
6.2 Sweet spot
6.3 Chromatic abberation
6.4 Vignetting
6.5 Distortion


7. Filters
7.1 Types of filters
7.2 Size of round filters
7.3 Size of rectangular filters
7.4 Filter as protection
7.5 Which UV or clear filter to get?
7.6 Multi-resistant coating
7.7 Filter for antireflection, darkening, contrasting and intensifying
7.8 Filter for blurring, diffusing or softening
7.9 Filter for coloring, special effects

8. Other elements in front of lens
8.1 Lens cap
8.2 Lens hood
8.3 Lens stepping rings
8.4 Lens-filter series adaptors

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1. DSLR lenses in general

Reading: Tamron Learning Center, A Consumer's Guide to Lenses - Part II from Sympatico MSN


1.1 What lenses is all about?

The important criteria to look into what lenses to get is basically all in understanding what a lens is used for.

A lens is a casing with a lot of lens elements within, which (1) let light through, (2) control the aperture size, and (3) focus the light onto the right place. Therefore it (1) controls the degree of brightness by virtual of its glass quality, (2) controls the limits of the aperture size settings, and (3) determines the degree of sharpness or, on the other hand, focusing aberrations.

As the elements moves within in relationship to each other, the optical centre moves, thereby giving what is called the zoom, or actually a variable range of focal length.

So practically the noticeable specification about the lens is
1. maximum aperture size
2. focal length

Before you ever need to know what lens you need to get, you must know this two factors above. if not, no point getting new lens.

The other features are
3. image circle (which determines whether it can cover a full frame 36 x 24mm sensor)
4. autofocusing ability and speed of autofocusing
5. the glass: resultant optical quality in terms of sharpness and colors

You may realised that certain performance factors are neither mentioned in the naming nomenclature, or quantified in the specifications given. Such factors include its optical quality in terms of sharpness and clarity, which is difficult to measure because of variable sharpness at different focal length and different aperture, which thus means that they can only be represented with a complicated graph but not with a single figure. Presenting such information may also affects manufacturer’s marketing, which means certain information are deliberately concealed or made elusive. As for clarity which is about how the light passed through the medium, it is determined by the number of the glass elements and the clarity of each glass elements (the former being specified, but not the latter). Also, the autofocusing ability of the lens also determine how fast the lens autofocus to an appropriately contrasted subject. Again this is not quantifiable unless a defined subject, distance and lighting is set.



1.2 A lens is a group of lenses: each of the components called a lens elements

Each piece of glass or plastic, irregardless of shape, redirects the light in a certain angle, and contribute as an "element" in a lens. In a way, when we call that black tubular device a camera lens (singular), it is actually a combination of different lenses (plural), which change distance from each other, with a complicated redirection of light to give an overall optical centre in each focal length setup. Hence, each lens is an element, while different lens element are grouped into small functional groups, and finally different groups combined with the casing of the lens (called the barrel) to form the final product. Hence we conventionally refer to groups of lenses (elements) as simply a lens.

The number of groups and elements are often specified, and are often, but not always, proportional to the range of zoom of focal length, and the overall length of the barrel. As light degrades through a larger number of groups and elements, the less groups and elements the better for the overall lens quality, which is why simple primes with only 1 focal length each, has a small number of groups and elements and is sharp. Zooms, on the other hand, may not be that dependent on the number of groups and elements, as the quality of each lens element may also make a big difference - i.e. a 17-35mm with less elements but lousy glass, may have poor quality, as compared to maybe a 18-70mm with more elements but good glass.

The front of the lens pointing towards your subject is called the front, with a front (lens) element and a lens cap (when front is not used, it usually means the front). The back of the lens is where it joins the camera body (look below on more for mount and fittings) and this back is called the rear. As such, the element that is exposed behind is called the rear element and the cap that covers it is called the rear cap (note that if you mention simply a lens cap, it will be taken for granted to be the front).



1.3 Aperture size: What is meant by a fast lens?

A fast lens doesn't mean it is fast in auto-focus, but simply means it has a large maximum aperture that will allow the shutter duration to be shorter at the same ISO. This usually means a lens with a maximum aperture of f/2.8 and smaller f-stop number. As mentioned above, the maximum aperture will be stated as a standard portion of a lens naming nomenclature. Supposed that 2 lens put together in the same lighting condition, set with the same ISO, if both lens is set at f/4, they will have the same shutter duration. but if one of the lens have a max aperture f/2.8 while the other one is f/4-5.6, the fast lens with f/2.8 will be able to push up the aperture size from f/4 to f/2.8 by 1 stop and thereby shortening the shutter duration to half.



1.4 Focal length: Prime versus zoom

Basically, you have to understand what is a focal length. It is again, the distance between the sensor to the optical centre of the lens, which will give you the resultant angle of view, field of view, composition and perspective.

Prime means fixed focal length, e.g. a 50mm lens will have that fixed distance between the sensor and the optical centre, thereby giving a constant angle of view, field of view, composition and perspective. Do remember, that it is only the focal length that is fixed, the aperture size can still varies and will always have a range of options between the maximum to the minimum, thereby allowing for photography with a range of control over exposure.

Zoom means a range of variable focal length. The name simply comes with the change of magnification of subjects with a change of angle of view, field of view, composition and perspective, which by common laymen term means zoom in and out.

Zoom lens tend to have
1. more lens elements and groups
2. more sophisticated lens design
3. more likelihood of optical abberations
4. decreasing optical quality with increasing range
5. increasing barrel length with increasing range

but this is not always the case, as efforts in sophisticated design may reduce or even reverse some of the above features.



1.5 Focal length: Standard and kits

Standard lens refers to the focal length that produces an angle of view that is relatively similar to the sharp portion of our vision (remember that our total vision is special and is not exactly limited to an angle; we see wider than that but there is a certain area that is sharp and a certain area that is not so sharp and we are only aware of movements, which explains why the scenaries are often breathtaking but often our photos do not feel the same even with the closest resemblance of exposure and color with its latitude). The industrial standard is set at 50mm by the lens. Regardless of the sensor size of the camera body, the "standard" refers to the focal length of the lens, not the resultant angle of view of the picture.

Kit lens refers to the most basic startup lens that is recommended by the manufacturer and sold as a set with the body, typically the lower ends one. Kit lens used to be lower quality primes but now usually with the lower quality zooms that covers the wide and the short tele range around the standard focal length of 50mm, typically 18-55mm.

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2. DSLR lenses features


2.1 Types of connection

Bayonet connection

Extracted and slightly rephrased from wikipedia, "a bayonet connector is a fastening mechanism that is locked by pins with matching slots and a spring that maintains a clamping force."

It looks like this from wikipedia, by author Iainf. Using abcsvg to convert the original svg file to jpg file, it looks slightly different like this. That thing on the right is not a hole but a protruding pin.

I loaded this directly to share as this is mentioned in the wikipedia: This file is licensed under Creative Commons Attribution 2.5 License
In short: you are free to distribute and modify the file as long as you attribute its author(s) or licensor(s).

"This style of connector was named after its initial implementation for soldiers who need to mount bayonets to the ends of their rifles in a hurry. The same need also applies to photographers who may need to change lenses quickly. The strength of the joint relies solely on the shear strength of the pins.

To couple the two surfaces, users are expected to align the pin(s) on the male with the slot(s) on the female and push the two together. Once the pins reach the end of the slot, a mechanism will guide the pin into another slot that prevents it from being removed. The spring then holds the pin in this position to prevent it from backing out. To disconnect the two surfaces the user will press a control that will overcome the spring and uses a fraction of a turn to reverse the locking turn."

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