How to choose a camera (the sensor format method)


#1
Hi,

Buying a camera can be a daunting task given the many options out there. This brief note explains how to distinguish between cameras by using the sensor format as a guide. With this information you can narrow down your choices and make a purchase that may be more suitable for your needs.

A digital camera captures images by recording light. It does this by using a light sensitive sensor inside it. The size of this sensor and technology used is related to the quality of the image and the hence the price of the camera. The image quality can usually be judged on the basis of dynamic range, image noise and resolution.

Dynamic range is the ability of the sensor to correctly map the contrast and shades of colors that occur in a scene. A sensor with better dynamic range will result in more accurate image color and contrast.

Image noise is the grain you may sometimes see on digital images. The grain generally becomes more visible when photos are taken in dimly lit situations. Too much image noise can lead to loss in detail, and so it is undesirable and affects the overall image quality.

Image resolution (the number of megapixels) is sometimes taken very seriously by camera buyers. In the last few years camera makers have pushed forward the idea that more megapixels means better image quality, but this isn't necessarily true. More megapixels does indeed mean more detail - which can be useful if the image needs to be cropped or for very large prints. But at the same time more megapixels can also lead to more noise, which is not good for the overall image quality.

A larger sized sensor usually equals a better quality image, meaning less noise, better resolution and better dynamic range. But cameras with larger sensors also tend to be more expensive.

The sensor size is usually published in the detailed specifications of the camera, which may be found on the camera box or manual. You can also try searching on the internet as many tech websites also publish this information.

The most common types of sensor sizes available right now are: 1/2.5”, 1/1.6”, four-thirds and APS-C. An illustration is shown below:

Source: Image sensor format - Wikipedia, the free encyclopedia

As you can see the sensors can vary quite a bit in size.

The available camera genres are as follows:
1. Mobile phone cameras
2. Point & Shoot (P&S) models such as Ultra Compacts, Compacts and Superzooms.
3. Advanced Point & Shoot models.
4. Compact System Cameras, also called Mirrorless or Interchangeable Lens Cameras
5. Entry level DSLRs
6. Semi professional DSLRs
7. Full-frame DSLRs
8. Medium-format DSLRs

Many of the above genres can be grouped by image sensor size, and hence approximately by image quality. Here are a few short notes on each sensor size.

On 1/2.5” sensors:
Mobile phones, Point and Shoot cameras and many Superzoom cameras tend to use the 1/2.5” sized sensor or a sensor of similar size.

The differences between cameras will lie in the quality of lenses used and features such as manual control, RAW capability, and internal camera and PC software. A sharp lens will help the camera to fully maximize the potential of the sensor, and extra features will allow for those with skill to produce good image quality in most situations.

If lens quality is the deciding factor in your purchase then take note that longer lens ranges generally results in less sharpness and hence less detail resolved in the final images. For these reasons Superzoom cameras generally don't produce the very best image quality and should be avoided unless there is a specific need to get up close to the subject.

1/2.5” sensor cameras cover many of the general and specific requirements of the consumer market with features such as macro, high zoom, portability, water resistance, shock resistance etc. Examples of this genre are the Canon Ixus, Canon Powershot A series, Olympus SW, Panasonic TZ series, the majority of phone cameras etc.

On 1/1.6” sensors:
These are larger sensors generally found in advanced P&S models. The larger sensor means you get better dynamic range and less noise in dim conditions, leading to better image quality.

Though more expensive on account of the larger sensor, these cameras normally also come equipped with better quality lenses and more features. Examples of the genre are the Panasonic LX7, Canon S100, Canon G12, Olympus XZ-1, Samsung EX-1 and Nikon P7700.

1/1.6" sensor cameras are favored by hobbyists and professionals who just don't want to lug around heavy DSLR cameras.

On Four-Thirds sensors:
The Four-Thirds (4/3rds) sensor was developed originally by Olympus and Kodak as an alternative to the APS-C sensor. At the time of development the claim made by Olympus was that most viewing platforms (computer and TV screens) used 4:3 aspect ratios, and therefore it was logical that sensors should be developed to match this aspect ratio.

The 4/3rds sensor has been used in Olympus DSLR cameras such as the now outdated miniature E-410 and the more recent giant sized E-5. These sensors have proven to be only very slightly less capable than their APS-C counterparts even though they are smaller in size. The fact that 4/3rds competes well with APS-C is testament to the great technology that goes into these sensors.

Olympus has since moved almost all their resources into the “micro” 4/3rds camera production and very few (if any at all) DSLRs are produced by the company anymore. Note that "micro" 4/3rds does not mean a new sensor size. Rather it refers to a new and smaller compact camera shell that houses the very same 4/3rds sensor.

The “micro” 4/3rds camera genre is a subset of the mirrorless camera category. Mirrorless cameras are also sometimes called "Compact System Cameras" or "Interchangeable Lens Cameras". It is a new genre and is discussed later on in this note.

On APS-C sensors:
The APS-C sensor is by far the most commonly used amongst hobbyists and professionals. This sensor represents a very good balance between the smaller 1/2.5” sensor and the generally more expensive full-frame sensor.

The APS-C sensor normally offers significant improvements in dynamic range and image noise compared to the 1/2.5” and the 1/1.6” sensor. If you compare sensor sizes it is obvious why this is so: APS-C sensors are at least eight times larger than 1/1.6" sensors and fourteen times larger than 1/2.5" sensors!

DSLR cameras, with the exception of Olympus models (4/3rds format), generally use APS-C sensors inside them. DSLRs are also feature rich, offer lens interchangeability and very good flexibility compared to other camera genres.

The APS-C sensor is generally used across a wide market range of DSLRs - from entry level (E.g - Canon 650D) up to the professional grade (Canon 7D). However the image quality, provided similar lenses are used, does not change significantly within the range.

For more details on DSLRs refer to this excellent FAQ thread by Rashkae:
FAQ: What DSLR camera to buy?


On 4/3rds sensors and APS-C sensors in Mirrorless cameras:

Mirrorless cameras are a new genre of camera that make use of the larger sized 4/3rds or APS-C sensor inside a smaller and lighter camera body. This is achieved through improvements in sensor technology allowing the composition of images solely using "live-view", hence eliminating the need for the mirror-box (see illustration below).


Source: Samsung NX System NX10 Hybrid DSLR

The mirror (shown in image-left) is a mechanical element that works with the optical viewfinder. When using a DSLR composition is done using the viewfinder. When the shutter is pressed the mirror moves out of the way exposing the sensor to the scene.

The sensors used in mirrorless cameras are efficient at processing light in real-time (called live view). Light enters the lens and is captured directly by the sensor with no intermediate mirror involved. Composition is done exclusively using electronic images through the rear screen or electronic viewfinder.

continued below...
 

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#2
The elimination of the mirror-box is an exciting development and perhaps the future of the digital camera. Mirrorless cameras are smaller and lighter and hence more easier to carry. The replacement of mechanical components with electronic components should also mean better durability and lower manufacturing costs due to simpler design.

The development of this genre has been very fast. Lens options are now good and adaptors can be made use of for older lenses and other mounts.

Common early complaints on mirrorless cameras were shutter lag, poor auto-focus speeds, lagging electronic viewfinders etc. However these problems are now resolved with better technology. Though manufacturers are at present seemingly only targeting the casual and hobbyist photographer, it is likely that good professional bodies will become available in the not too distant future.

In summary mirrorless cameras offer DSLR like image quality in smaller, compact bodies. Examples of mirrorless cameras are the Panasonic G and Olympus E series (4/3rds sensor), and the Sony NEX and Samsung NX series (APS-C sensor).

On Full Frame and Medium Format cameras:

Full-frame and medium format sensors are the largest commercially available imaging sensors in the market. The full frame sensor mimics the size of the 35mm film size, and is approximately two and a half times the size of the APS-C sensor. The medium format sensor is in turn two and a half times larger than the full frame sensor! Both sensor types tend to have very high megapixel counts.

Examples of full-frame sensor cameras are the Canon Mark 5d and the Nikon D700. Examples of medium format sensor cameras are most Hasselblad cameras and the Pentax 645D. In line with the size-quality trend these larger sensors produce significantly better image quality but also tend to cater to the premium and highly specialized markets.

Whilst full-frame sensor bodies are priced within range of high specification APS-C models, medium-format based bodies tends to be priced at a significant premium over full-frame bodies. Since full-frame and APS-C sensors cater to most modern professional needs it is becoming increasingly difficult to justify the additional cost of medium-format bodies. Similarly the APS-C sensor also poses a serious challenge towards full-frame by providing increasingly better image quality with new technology.

On SLT cameras:
The SLT camera is a new camera genre at present only manufactured by Sony. The camera uses a mirror similar to those used in DSLRs. However the mirror is fixed and translucent in order to allow light through to the sensor for image capture (also called the pellicle mirror). This is different from the DSLR where the mirror swivels out of the way for light to reach the sensor. See illustration below.


Source: http://woofie1.pixiq.com/files/penta_3.png

By using a fixed mirror Sony is able to design a camera that is more compact than a DSLR while still using the APS-C sensor. In addition the camera retains much of the features of the DSLR including phase-detect auto-focus, good battery life, and the Alpha lens mount.

Conclusion:
The sensor size is important to image quality and it is also what frequently decides the price of cameras. By understanding the different sensor formats and camera groups choosing the right camera becomes easier to do.

Some sensors have not been discussed in this article - for example the rather unique Nikon 1" sensor, the Pentax Q series sensor and the Sigma Fovean sensor. However the general trend of larger size equals better quality still applies and should prove to be good guidance.

For those of you who are still unsure, my personal opinion is that, at the time of writing this, 4/3rds and APS-C sensor based cameras offer the best image quality for the money.

I hope this article makes sense. Suggestions for improvements are most welcome.

Thanks for reading. I wish you the best of luck in finding the right camera for your needs!
 

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#5
The first thing that leaps to mind is that there is no mention of FF cameras..
I have specified somewhere mid-way in post 1 that I am not discussing FF in this note. Since this note is meant to be more for the newcomer and hobbyist. I presume that the FF buyer would already be sufficiently experienced in camera technology in order to understand the differences between sensors. :)
 

luckyorange

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#6
nice thread =), one more thread for those who want to buy but dont know which model to choose

:thumbsup:
 

edutilos-

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#7
I have specified somewhere mid-way in post 1 that I am not discussing FF in this note. Since this note is meant to be more for the newcomer and hobbyist. I presume that the FF buyer would already be sufficiently experienced in camera technology in order to understand the differences between sensors. :)
Ok, thanks for the clarification.

You can build on it eventually, for example, one common query is amount of depth of field, another is the crop factor relating to one focal length used on different sensors...
 

#8
Ok, thanks for the clarification.

You can build on it eventually, for example, one common query is amount of depth of field, another is the crop factor relating to one focal length used on different sensors...
Good points.

Depth of field is a consideration but I have to bring lenses into the discussion to explain what it means. This might complicate the note a bit. I am trying to keep it as simple as possible.

Crop factor is also important but only when worrying about lens focal ranges. I guess this can be discussed in a specific DSLR lens thread.

My main aim was to make choosing a camera more easily by focusing on image sensor format. So my note focuses on the pros and cons of the sensor formats and the the types of sensors common cameras use.
 

Octarine

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#9
The term 'Image Quality' remains blur and requires further explanations, imho. Here the topics Noise and Resolution could come in. Another point is the Mega Pixel Race and its side effects.
 

#10
The term 'Image Quality' remains blur and requires further explanations, imho. Here the topics Noise and Resolution could come in. Another point is the Mega Pixel Race and its side effects.
My original post briefly introduces the concept of noise.

Resolution is not so important I suppose because the Megapixel race has slowed down quite a lot. But I agree that many new buyers take it seriously. I have modified the original post a little to talk about it.
 

daredevil123

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#12
Good points.

Depth of field is a consideration but I have to bring lenses into the discussion to explain what it means. This might complicate the note a bit. I am trying to keep it as simple as possible.

Crop factor is also important but only when worrying about lens focal ranges. I guess this can be discussed in a specific DSLR lens thread.

My main aim was to make choosing a camera more easily by focusing on image sensor format. So my note focuses on the pros and cons of the sensor formats and the the types of sensors common cameras use.
Good job. But do also note that crop factor also affects depth of field attainable. It will be good to cover that as well.
 

NikF601

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#14
Effort compiled into layman reading and decision making for first DLSR ... Great
 

#16
Thanks all for the kind comments.

Good job. But do also note that crop factor also affects depth of field attainable. It will be good to cover that as well.
In this thread I was basically aiming to explain the following.

1. The basic image quality is related to sensor format
2. The sensor format is related to price
3. What camera genres are associated with these sensor formats

Umm.. DOF will fall under the image quality segment. But this is not an easy concept to explain in a few short words since DOF is related to aperture and focal length. I am trying really hard to keep this thread as basic as possible.

Since there is a lot to say, it may be better to discuss DOF in a separate thread.
 

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ZerocoolAstra

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#17
Good thread.
I see you're trying to keep it as simple as possible, which is ideal so as not to complicate the decision making process for newbies.
Would you consider adding in some illustrations?
Especially to highlight how the mirror-less camera achieves a size reduction compared with the traditional DSLR..

for example, a diagram like this

http://www.whatdigitalcamera.com/imageBank/e/ep1-diagram580.jpg
 

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#18
Good thread.
I see you're trying to keep it as simple as possible, which is ideal so as not to complicate the decision making process for newbies.
Would you consider adding in some illustrations?
Especially to highlight how the mirror-less camera achieves a size reduction compared with the traditional DSLR..

for example, a diagram like this

http://www.whatdigitalcamera.com/imageBank/e/ep1-diagram580.jpg
Thanks a lot.

Illustrations are a very good idea and I was definitely thinking about doing this.

I will update the thread tonight.
 

ed9119

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#20
This thread is now accorded 'Sticky' status ....... thanks for gathering the research and info bro '

ed
 

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