Confuse "50mm is closer to what our eyes see'

[dreamer_toons]

Hi ,

People often refer to 50mm len as they are closer to what our eyes preceived. In FF, 50mm is always 50mm; however with a crop factor of 1.5, 50mm will become 75mm. So how is this relate to the 'closer to what our eyes preceived'?

With a crop factor of 1.5, wouldn't a 35mm more suitable and closer to our eyes' vision? Please advise a newbie, Thanks.

 

[Parchiao]

It's only because we used to live in the world of 35mm film.

 

[zac08]

Hi ,

People often refer to 50mm len as they are closer to what our eyes preceived. In FF, 50mm is always 50mm; however with a crop factor of 1.5, 50mm will become 75mm. So how is this relate to the 'closer to what our eyes preceived'?

With a crop factor of 1.5, wouldn't a 35mm more suitable and closer to our eyes' vision? Please advise a newbie, Thanks.

Yes... you're right. So most of the users are still pointing to a 35mm full frame view instead. Waiting for the full frame DSLRs to be more affordable.... :sweat:

 

[walltakespigchairs]

Perspective wise 50mm shows everything at the same size. The 1.5x crop does nothing to change the size of objects throught the viewfinder, the only difference being that we have a certain percentage of the edges cut off. The smaller dx/aps-c sensor takes whatever image the centre area of the lens projects thus the decrease in the viewing angle of the lens.

 

[sammy888]

In really lay man's term. This "famous" saying came about a long time back way before we even saw a Digital SLR. Since majority of DLSRs today have a crop factor of 1.5 or there about....that "saying" no long holds truth.

Now if you want to know how that claim came about donkey years ago here is a simple explanation:

"The 50mm lens comes closest to the human eye's perception of distance and depth. The compression of the image is very close to what your eye can see, as opposed to the compressing effect of a telephoto lens or the stretching of distance between objects by a wide-angle lens."

But in the real world that claim can not literally be taken too seriously since the eye's field of vision is about 110 degree (+/-) while the 50mm is about 60 degree.

 

[LittleWolf]

"The 50mm lens comes closest to the human eye's perception of distance and depth. The compression of the image is very close to what your eye can see, as opposed to the compressing effect of a telephoto lens or the stretching of distance between objects by a wide-angle lens."

This is a bogus attempt at an explanation - neither do telephoto lenses "compress" distances, nor do wide angle lenses "expand" them. Pictures taken from the same position with a tele lens are the same as a cropped version of a wide angle photo.

 

[sammy888]

This is a bogus attempt at an explanation - neither do telephoto lenses "compress" distances, nor do wide angle lenses "expand" them. Pictures taken from the same position with a tele lens are the same as a cropped version of a wide angle photo.

It has to do with depth perception. Its how our eyes view the 3D world and you get a perpective view that let you tell object from nearest one to the furthers.. When we use a telephoto and wide angle there is some distortion and that change in perspective. That's what I meant. This 50mm has the closest perception to the human eye.

If you feel you could do better then explain it. I am willing to learn to explain it better. But if you want to come in and make a bogus rebutt and leave then I rather you not say anything but some lame half baked gibberish. Be a man. Don't show me your family upbringing in this manner.

 

[night86mare]

Hi ,

People often refer to 50mm len as they are closer to what our eyes preceived. In FF, 50mm is always 50mm; however with a crop factor of 1.5, 50mm will become 75mm. So how is this relate to the 'closer to what our eyes preceived'?

With a crop factor of 1.5, wouldn't a 35mm more suitable and closer to our eyes' vision? Please advise a newbie, Thanks.

my question to you would be - why care?

perception is what you make of it - some technicality with regards to focal lengths and whatever crop factor, etc, so that you can make educated purchases are definitely in order, but filter through the information you need and the information which you do not need. to me, i am perpetually amused by people who like to calculate, calculate and calculate but hardly walk the talk for all the "technical knowledge" they know. especially when you would rarely need to know all this stuff out in the field when shooting. everything else - you can always use the internet. there is a reason why it is the information age today.. GOOGLE IS YOUR BEST FRIEND.

to prove this, a quick search of "50mm field of view" took me 1/2 second including typing out those letters;

What makes a lens "normal?"

A "normal" lens produces a field of view that is similar to human vision. The diagonal of the image plane is typically used as the reference for field of view determination. A "normal" lens has a focal length that is approximately equal to the diagonal measurement of the image plane. When the focal length is equal to the diagonal measurement it produces a diagonal field of view of approximately 53° which is similar to human vision.

For 35mm film (24mm by 36mm), the diagonal measurement is 43.27mm. 50mm is close to this measurement so it is considered a "normal" lens. A 50mm lens produces a 47° diagonal field of view which is close to 53°.

source

if you don't understand all the technical jargon above, here is more better-written, better thought-out stuff by the panoramafactory site

What about digital cameras?

The CCD arrays on digital cameras are typically much smaller than the imaging area of 35mm film. This means that the focal length that produces a "normal" field of view is much smaller than 50mm.

Unlike 35mm film which is the same regardless of what camera you use, the size of the CCD array varies from camera to camera. This poses a problem. You cannot know whether a focal length is "normal", wide angle or telephoto without knowing the exact size of the CCD array. Unfortunately, even knowing the exact size of the CCD array may not help because sometimes the imaging area doesn't even cover the entire array!

Because many people are familiar with focal lengths of lenses for 35mm cameras, the digital camera manufacturers choose to describe the focal length of their cameras by reference to the focal length that would produce a similar field of view on a 35mm camera.

Consider, for example, a digital camera with a CCD array measuring 8.10mm by 6.08mm. The diagonal measurement of this CCD array would be 10.13mm. A lens with a focal length of 11.7mm would produce a diagonal field of view of 47°, the same as a 50mm lens on a 35mm camera. So for this camera, an 11.7mm lens would be described as having a 35mm equivalent focal length of 50mm.

By describing the lenses this way, the digital camera companies appeal to users' familiarity with 35mm camera equipment.

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Are all digital cameras the same?

Unfortunately the digital camera companies do not all use the same method for determining 35mm equivalency. There are at least three methods used by camera manufacturers.

Some camera companies use the diagonal field of view exactly as described in this article. That is, if they describe a camera as having a particular 35mm equivalent focal length, it means the camera produces the same field of view along the diagonal as a 35mm camera with a lens having the stated focal length.

Other companies use the horizontal field of view rather than the diagonal field of view. This produces a slightly different result from using the diagonal because the aspect ratio of the digital image (usually 4:3) is different from the aspect ratio of 35mm film images (exactly 3:2). When a digitial camera produces the same horizontal field of view as a 35mm camera with a lens having a particular focal length it actually has a larger diagonal field of view.

Finally, some companies describe the camera as having a 35mm equivalent focal length of 50mm if the focal length is exactly equal to the diagonal measurement of the CCD array and scale all other focal lengths accordingly. In this way they appeal directly to the idea that 50mm is the "normal" focal length. These cameras actually have a larger field of view in all directions when compared to a 35mm camera with a lens having the stated focal length.

Unfortunately, this means that one camera maker's 50mm equivalent may or may not have the same field of view as another. And you can't compare actual focal lengths without knowing the size of the image on the CCD array.

 

[night86mare]

This is a bogus attempt at an explanation - neither do telephoto lenses "compress" distances, nor do wide angle lenses "expand" them. Pictures taken from the same position with a tele lens are the same as a cropped version of a wide angle photo.

if we want to be truly technical, then you do not make sense

i could take pictures from the same position with my uwa 10mm now and my 50mm and i can tell you that there is going to be distortion in my 10mm image when i crop it. so how? :dunno:

if you must do something, go all the way. halfpastsix doesn't work most of the time :devil:

 

[calebk]

This is a bogus attempt at an explanation - neither do telephoto lenses "compress" distances, nor do wide angle lenses "expand" them. Pictures taken from the same position with a tele lens are the same as a cropped version of a wide angle photo.

Oh, I think you've confused your crop factors with your focal lengths...

Like that, I can shoot a 22MP photo with my 10mm, then crop the center out and get a lower res 200mm photo lah.

Sorry, I think this is a bogus rebuttal.

 

[grantyale]

Like that, I can shoot a 22MP photo with my 10mm, then crop the center out and get a lower res 200mm photo lah.

Actually this is correct :bsmilie:

 

[antacid]

Actually this is correct :bsmilie:

but wouldnt the depth of field and 'background compression' be different? like how the bokeh of a 15mm and a 200mm lens is different?

 

[Clockunder]

my question to you would be - why care?

perception is what you make of it - some technicality with regards to focal lengths and whatever crop factor, etc, so that you can make educated purchases are definitely in order, but filter through the information you need and the information which you do not need. to me, i am perpetually amused by people who like to calculate, calculate and calculate but hardly walk the talk for all the "technical knowledge" they know. especially when you would rarely need to know all this stuff out in the field when shooting. everything else - you can always use the internet. there is a reason why it is the information age today.. GOOGLE IS YOUR BEST FRIEND.

to prove this, a quick search of "50mm field of view" took me 1/2 second including typing out those letters;



source

if you don't understand all the technical jargon above, here is more better-written, better thought-out stuff by the panoramafactory site

As sammy888 said, that claim can not literally be taken too seriously since the eye's field of vision is a lot more than the 46.8 degree angle of view of a 50mm on the 35mm film format.

46.8 degree is just an approximation of our concentrated field of vision when a person concentrates on a portion of his/her field of vision.

 

[Clockunder]

This is also truth in what Littlewolf said about the focal lengths do not compress or expand distances.

Perspertive (i.e. relative sizes of things in the picture) is solely determined by the objects' actual relative physical size and their relative distances. So if we stand at exactly the same spot and take 2 pictures with different focal lengths, the perspective is the same except for the different field of view where the longer lens will have a narrower field of view which gives an illusion that distances are compressed. The word "illusion" is used because if you compare their relative sizes, the ratio of A size/B size is actually the same in both pictures even though different focal lengths have been used.

If you do a 1.5xcrop of a picture taken by 50mm lens on the Nikon D3, you can get a picture which has the same perspective as a picture taken by a 75mm lens on the D3 from the same spot. In other words, a 50mm lens on a Nikon D300 will not only have the same perspective but also the same field of view as a 75mm on Nikon D3 if taken from the same spot. This also explains why about 6mm focal length on a compact point and shoot camera gives the same picture as a 35mm lens on a full frame DSLR or 35mm film camera if both pictures are taken from the same spot.

You may then ask why would one buy a more expensive 75mm lens then if one can have the same picture just by cropping a picture from 50mm or why would anyone want to buy a DSLR if a much cheaper compact point and shoot camera can give the same picture.

Lens distortion, bokeh, lens resolution and picture resolution are separate issues from "perspective" and "field of view".

From the same distance and assuming same lens quality, a 75mm lens can resolve more details than a 50mm lens. This has to do with the demagnification factor which is focal length/distance.

As to the threadstarter's question, the answer is already given by the first poster who replied : we used to live in the 35mm film aka 135 format world.

 

[xEnie23]

This is also truth in what Littlewolf said about the focal lengths do not compress or expand distances.

Perspertive (i.e. relative sizes of things in the picture) is solely determined by the objects' actual relative physical size and their relative distances. So if we stand at exactly the same spot and take 2 pictures with different focal lengths, the perspective is the same except for the different field of view where the longer lens will have a narrower field of view which gives an illusion that distances are compressed. The word "illusion" is used because if you compare their relative sizes, the ratio of A size/B size is actually the same in both pictures even though different focal lengths have been used.

If you do a 1.5xcrop of a picture taken by 50mm lens on the Nikon D3, you can get a picture which has the same perspective as a picture taken by a 75mm lens on the D3 from the same spot. In other words, a 50mm lens on a Nikon D300 will not only have the same perspective but also the same field of view as a 75mm on Nikon D3 if taken from the same spot. This also explains why about 6mm focal length on a compact point and shoot camera gives the same picture as a 35mm lens on a full frame DSLR or 35mm film camera if both pictures are taken from the same spot.

You may then ask why would one buy a more expensive 75mm lens then if one can have the same picture just by cropping a picture from 50mm or why would anyone want to buy a DSLR if a much cheaper compact point and shoot camera can give the same picture.

Lens distortion, bokeh, lens resolution and picture resolution are separate issues from "perspective" and "field of view".

From the same distance and assuming same lens quality, a 75mm lens can resolve more details than a 50mm lens. This has to do with the demagnification factor which is focal length/distance.

As to the threadstarter's question, the answer is already given by the first poster who replied : we used to live in the 35mm film aka 135 format world.

i like wot u type.
35mm film days. ahaha. memories. anyw, it still in the individuals.
some prefer 50mm wid the 1.5 crop factor.
some prefer 35mm wid the 1.5 crop factor due to 3.5mm x 1.5 = get u somewhr near to 50mm.

but still. most professional would go for 50mm wor. somemore they arent using FF bodies..
pondering too :cry:

 

[JediForce4ever]

i like wot u type.

but still. most professional would go for 50mm wor. somemore they arent using FF bodies..

Not sure where you heard this, but I don't it is true.