Something I'd like to get clarified about the viewfinders in FF vs. crop cameras

Do objects appear at the same magnification in the viewfinders of crop and FF cameras when using a lens of identical focal length? Or do they appear smaller in the FF due to the greater FoV? In other words, is the viewfinder in the FF camera exactly 1.6 times larger than the one in the crop? Or is it smaller than that? Thanks in advance for clarifying this to me.

cfibanez wrote in post #8405521
Do objects appear at the same magnification in the viewfinders of crop and FF cameras when using a lens of identical focal length? Or do they appear smaller in the FF due to the greater FoV? In other words, is the viewfinder in the FF camera exactly 1.6 times larger than the one in the crop? Or is it smaller than that? Thanks in advance for clarifying this to me.

When I got a 5D and still had my 20D, I put lenses of identical focal lengths on the two cameras and held one up to each eye. I saw the actual object size as nearly identical, but the FOV of the crop camera was less and the wider black mask around it was obviously larger. It was obvious that the cropped camera presented a cropped view when I compared them side by side.

Added: The Sigma camera doesn't use a black mask, it uses a semi-opaque mask so that you can actually see the surrounding area that is "cropped" out when you view it through the Canon.

This is a tricky one. Actually both viewfinders will be stated for magnification using the same focal length. An example is probably best.

40D Viewfinder = 0.95X

5D Viewfinder = 0.71X

Now let's try some basic scenarios. First, suppose we use each camera to take the same picture with the same framing by using a focal length 1.6X times longer on the FF body - like using a 50mm lens on the 40D and an 80mm lens on the 5D. In this case items in the 5D viewfinder will look about 20% larger than in the 40D viewfinder. Incidentally, the entire 5D viewfinder rectangle is going to appear about 20% larger in all instances.

Now, your specific question was keeping the focal length the same. So in this second case let's go for totally different framing and just take the same shot with a 50mm lens on each camera. In this case subjects in the 40D viewfinder will appear to be about 31% larger than in the 5D viewfinder even though the 5D VF box will still be about 20% larger. This effect occurs because the 5D is taking a much more loosely framed shot.

Thank you. I am asking this because I have tried to look at the viewfinder of my 40D with one eye while directly looking at the same scene with the other (naked) eye and found that I can see the same object at comparable magnification with either eye when the 24-105 zoom is at approximately 50mm. This fitted nicely with what I have read about 50mm being the "natural" focal range of human vision. But since my camera is a 1.6X crop, I would have expected that identical magnification to real life would be reached in the viewfinder of the crop at focal lengths shorter than 50mm (e.g. 31mm). This led me to think that perhaps crop and FF viewfinders have the same magnification, but they are simply bigger in a FF camera.

If the viewfinder rectangle of the 5D is NOT exactly 1.6 X bigger than the one in the 40D (but only 1.2 X as Jeffrey says) then indeed objects will look smaller in the FF viewfinder than in the crop viewfinder.

I wonder if anyone has done this test and checked which focal length gives the same viewfinder magnification in a FF camera of objects seen with the naked eye.

As I said above, with everything else being equal, the image window appears dimensionally larger in the 24x36mm camera.

The magnification factor given in camera specifications is actually supposed to be a comparison of the objects as they would be seen by the naked eye. If a camera touted a 1:1 or 1x viewfinder magnification, that would mean "compared to the naked eye."

The variable they play with, however, is the focal length of the lens being used in the specification, and that is where DSLR manufacturers play it fast and loose by specifying a 50mm lens.

Since the beginning of SLR marketing, back in the late 30s, the primary marketing aspect of SLRs versus rangefinder cameras was a "big, bright, life-size image." But that was actually difficult and expensive to achieve, and not many cameras ever did. But it was always the case that you specified viewfinder magnification with the "normal" lens, and the "normal" lens is considered the focal length equal to the diagonal of the format.

You can alter the viewfinder magnification by either the focal length of the lens or the magnification of the eyepiece. But there is no free lunch--if you increase the magnification of the eyepiece, you dramatically decrease the brightness of the image.

That's the primary reason there was quite a bit of variation of "normal" up through the 60s--from 45mm (technically, it should be 43mm) to 58mm as manufacturers tried to get to 1x magnification without increasing the viewfinder eyepiece too much (that and the fact that it's a bit easier to design a slightly longer lens to be a bit faster).

But--and here is the important thing--the specification of viewfinder magnification was always with a lens at least nominally close to the diagonal of the image format. Obviously, if the manufacturer specified 1x magnification using a telephoto lens, that would be cheating.

Then came 15x22mm DSLRs using the same lenses as 24x36mm cameras. That--and the ubiquitousness of "standard zooms" allowed manufacturers to introduce a high level of confusion into their marketing. The concept of "normal lens" was lost to most newcomers--they didn't know what the standard measuring point was.

In actually, the "normal" lens for the 15x22mm format is about 28mm.

But given the opportunity to confuse newcomers, manufacturers quoted the viewfinder magnification of their new 15x22mm cameras with the same 50mm lens as their 24x36mm cameras...even though a 50mm lens is a telephoto on a 15x22mm camera.

Thus, even though a 50D may be advertised as having a much higher viewfinder magnification than a 5D, if you hold each up to your eyes with a 50mm attached, the subject in the 5D viewfinder is still clearly larger and clearly closer to life-sized.

If you put a 28mm lens--the "normal" lens--on that 50D, you see a true comparison. The FOV will be equal to that of a 50mm lens on the 5D, and the size of the 5D image window will still be much greater.

The subject or the image is always larger by every definition in the 5D viewfinder, given equal focal lengths or using the "normal" lens on both cameras.

^Thank you for taking the time to write this. It's been most useful!

cfibanez wrote in post #8408792
This fitted nicely with what I have read about 50mm being the "natural" focal range of human vision.

It sounds like you're understanding the truth. The information you've read about the 50mm focal length, though, is wrong. Folks over the years have totally buggered up the truth about what a "normal" focal length on a camera does. It has absolutely nothing to do with what you see through a viewfinder as compared to looking at the same scene with a naked eye.

As far as I know, a "normal" lens is supposed to frame about as much of the subject as we recognize, when we look at it with our naked eyes. As you know, we can detect movement within almost 180°, but we normally don't care much about what's happening behind our ears. We see a part of the view in front of us clearly, and that part is about what you capture with a normal lens, if you take a photo.

apersson850 wrote in post #8409499
As far as I know, a "normal" lens is supposed to frame about as much of the subject as we recognize, when we look at it with our naked eyes. As you know, we can detect movement within almost 180°, but we normally don't care much about what's happening behind our ears. We see a part of the view in front of us clearly, and that part is about what you capture with a normal lens, if you take a photo.

Defining a "normal" lens focal length has absolutely nothing to do with what you see through a viewfinder, though. Many folks believe, quite incorrectly, that with a "normal" lens on the camera you should be able to see a scene with one eye and look through the viewfinder with the other and see things at the same size.

The optics in the viewfinder system can be radically different from camera to camera - even cameras with the same format ("format" refers to the size of the film frame or digital sensor in a camera), and this will change what you see in the viewfinder.

The focal length of a "normal" focal length lens is typically about the same as the diagonal dimension of the film/sensor frame in the camera.

An image made with a "normal" focal length lens will appear to be about the same as the real-life view when the image is viewed at a distance roughly equal to the diagonal of the print (or display).

SkipD wrote in post #8409846
Defining a "normal" lens focal length has absolutely nothing to do with what you see through a viewfinder, though. Many folks believe, quite incorrectly, that with a "normal" lens on the camera you should be able to see a scene with one eye and look through the viewfinder with the other and see things at the same size.

The optics in the viewfinder system can be radically different from camera to camera - even cameras with the same format ("format" refers to the size of the film frame or digital sensor in a camera), and this will change what you see in the viewfinder.

The point I'd make here, with reference to what I wrote above, is that gaining a 1x viewfinder magnification with the normal lens had been the goal of SLR manufacturers (or at least their holy grail).

I think what you're saying is that the cart has to be properly behind the horse. With regard to viewfinder magnification, manufacturers had the concept of the "normal" lens first, then designed the viewfinder system to reach the goal of 1x magnification (or as close to it as the price point of the camera will allow).

While this is true, I have not been able to determine which came first, the chicken or the egg. It appears to me that (like the Circle of Confusion) this concept is a "back calculation" from a few decades of empirical data of what focal lengths produced pleasing perspective.

I suspect that early photographers discovered emperically that a certain focal length for each format provided a workable balance between ease of use and pleasing perspective and then noted that focal length tended to equal the diagonal of the format.

Certainly by the time Barnack chose 50mm as the "normal" focal length for his Leica, that formula had become a standard.

I don't know about this. You mean an uncropped print, right?

Here is a comparison I did of the relative sizes and field of view for the viewfinders in all of the major cameras

https://photography-on-the.net/forum/showthre​ad.php?t=465469

From this you can visually see what the same scene would look liek if you viewed if from any of the cameras. This comparison assumed that you compared the same field of view (ie 16mm on FF and 10mm on 1.6x crop)

Sorry about not staying completely on topic but simce i dont know i will ask.
Are there benefits to using a ff cameras viewfinder compared to a crop?

That's awesome BigBlueDodge. Thanks! I had always heard that FF viewfinders were larger, but wow, that's a big difference.

BigBlueDodge wrote in post #8413446
Here is a comparison I did of the relative sizes and field of view for the viewfinders in all of the major cameras
https://photography-on-the.net/forum/showthre​ad.php?t=465469
From this you can visually see what the same scene would look liek if you viewed if from any of the cameras. This comparison assumed that you compared the same field of view (ie 16mm on FF and 10mm on 1.6x crop)

Thank you. While it is obvious that the mountains look bigger in the 5D viewfinder than in the 40D at comparable FoV, this is not exactly what I was asking. My question was simply whether the mountains will look bigger, smaller or the same using the same focal length in the two cameras. When discussing the concept of viewfinder magnification, I mentioned at some point the idea of a "normal" lens which somewhat derailed the original question I had in this thread.

Thanks to the collective wisdom at POTN, however, not only did I get the answer to my question, but also learnt a number of things:

1) Viewfinder magnification has in principle nothing to do with what our naked eye is able to see, although this has apparently been a goal of camera manufacturers. The fact that magnification in the viewfinder of the 40D is 0.95X at 50mm nicely explains why I could see objects at the same magnification through the viewfinder and my naked eye at this focal length.

2) That this was the case, however, has nothing to do with what a "normal" focal length is. This is defined in relation to the size of the film or sensor of the imaging system in question.

3) The manuals of the 40D and 5D state (at the very end though) that viewfinder magnifications for these cameras are 0.95X and 0.71X, respectively, when using a lens of 50mm. This does in fact answer my original question: objects will appear smaller in the 5D viewfinder at the same focal length.

4) This is because the 5D viewfinder, although bigger than the one in the 40D, is not exactly 1.6X bigger (as the crop factor would require) but only about 1.2X bigger (this follows from (1.6/0.95)*0.71=1.19).

5) I've also learnt that many of these concepts are in fact basic knowledge in photography, from which my ignorance in these matters has become thoroughly exposed. Fortunately for me, POTN is a friendly place and senior members do not mind to be patient with inexperienced people like me that are just too lazy to grab the books and read (!)

Cheers!