[weinzierl]

I never understood that argument. By pure FOV the human eye is much wider. Of course it is not that simple, spacial resolution drops off to sides (while temporal resolution increases). This makes statements like "50 mm on 35 mm is FOV of human eye" not very meaningful.

[fsckboy]

if you take a 35mm SLR with a 50mm lens and rotate it vertically (portrait) and hold the viewfinder up to one of your eyes, and leave the other eye open, your binocular vision will merge the two images with no problem/distortion, as if you were not holding a set of lenses up to one eye.

since what you see through the viewvinder is what the taken picture will look like, it is neutral like/wrt your eyes, at the zero middle between wide angle and telephoto. (it's worth considering "who says eyes are neutral?" it's the system we are used to and our brain develops to understand)

it's non obvious to a casual observer that the mm units chosen for the image size (the image gets focused on a 35mm rectangle (you need to know the aspect ratio)) and mm for the focal length are measuring different things, but that's why you just need to "know" that 35mm and 50mm "equal neutral". there are more things measured in mm as well, like the actual width of the primary lens which indicates how much light is gathered to be focused onto the same square.

i'm not a photographer. i don't quite know the mm lingo for what happens when the image sensor/film is wider then 35mm, the large/full formats. the focal lengths "work" the same, but a larger image would need to be focused and that seems like it would require some larger distances within the lens system.

[namibj]

The large format ones get a higher FOV in degrees. IIRC if you keep absolute aperture the same and change focal length to keep FOV the same, the DOF won't perceptually change.

Now, when you realize that there are geometric limitations to how wide an aperture can be relative to the focal length without having to stray from vaguely traditional _shapes_ of the objectives ("camera lens"), you can see that at the expense of fancier abberation corrections and of course larger/heavier glass lenses making up the larger objective, one could use a proportionally wider aperture with large format cameras.

For example, the infamous Barry Lyndon objectives were actually "just" 0.7x teleconverted spinoffs from an originally 70mm f/1 design. https://web.archive.org/web/20090309005033/http://ogiroux.bl...

[dghlsakjg]

The phenomenon you describe is a function of viewfinder magnification. It so happens that many SLRs had their magnification such that it worked well at 50mm to shoot with both eyes open. There are SLRs that have different magnification so this trick doesn’t always work.

You can get a rangefinder style camera with a viewfinder that lets you shoot with both eyes open but has a 35mm POV.

People have a variety of theories as to why 50mm is considered the standard lens and why people say it mimics human vision. I have heard so many explanations that I am inclined to say that there’s not really much but opinion behind it. It might just be that it was the most common first lens and because it is cheap and relatively simple to make a good, fast 50mm lens.

[fsckboy]

if that trick doesn't work, then either 1. your viewfinder is not showing what you will shoot which is what everybody expects because otherwise how can you frame your shot, 2. you are not using a 50mm lens or 3. you are not using a 35mm SLR

the point of a "single lens reflex" system is that you can see what the picture will look like by looking through the same (single) optics

[dghlsakjg]

No. As I stated, if the trick doesn’t work at 50mm it is because you are using a viewfinder with a different magnification.

A Pentax MX for example shows .97x magnification at 50mm. It will work great for your trick. Meanwhile a Canon AE-1 has .83x magnification at 50mm meaning one eye will be seeing an image where everything is 17% different in size. It will be like one eye is looking at a 55 inch TV and the other eye is looking at a 45 inch TV. Or more accurately, one eye is looking at the same TV but from 17% farther away.

If you throw a 58mm lens on that Canon, the trick will work again because you are zooming in to compensate for the zooming out that is happening in the viewfinder.

Of course, none of this has anything to do with 50mm lenses being “standard”.

Don’t believe me? Go slap a 50mm lens on an SLR with very low magnification. Or read one of the dozens of articles and threads out there explaining your misconception. Here’s a great one: https://www.lomography.com/magazine/319909-cameras-in-depth-...

[fsckboy]

technically speaking, if your viewfinder has a different magnification, that is (to coin a word) Multiple Lens Reflex; you have added a lens. SLRs were invented to show you "what the camera sees" so you can tweak it perfectly on different dimensions.

you are describing a different system that does not show you what the camera sees. I'm not saying what you are talking about doesn't exist, I'm saying that your over-inclusivity takes away the value of describing what I described and is telling people "there's really nothing you can say, a million different things could be going on"

[dghlsakjg]

Every slr with an eye level viewfinder (instead of focusing on a waist level ground glass) has optics in it. It is an MLR by your wording. Your eye has to focus on the reflection of a ground glass within an inch or so, or else is viewed through a lens that makes it possible to see what the camera sees. You wouldn’t be able to focus with your eyes if there wasn’t another lens.

In other words, your “standard” lens is an artifact of the optics chosen to allow your eye to see the image.

In terms of what your eye sees: The FOV of what you are focusing on with your eyes is narrower than a 50mm lens. The FOV where your eyes can recognize symbols (can read letters) is wider than a 50mm lens. The FOV that your eyes can see from periphery to periphery is drastically wider than 50mm.

Quite simply put, the fact that on some cameras you can shoot with both eyes open at 50mm is an artifact of design, not some natural law. This is proven by the fact that there are cameras where you can do this with a 35mm lens or a 60mm lens. Camera manufacturers settled on calling 50mm at 1.0x magnification a standard view is arbitrary.

There is precisely nothing behind the common belief that 50mm is the same view as your eyes. It isn’t.

You can keep insisting otherwise, but it is in contradiction with physics and nominal human anatomy.

[fvgvkujdfbllo]

The way I understand is that it is not FOV but zoom level. If you look through a camera with 50mm lens, the subject and background should appear same size as when viewed with naked eyes. Doesn’t matter if it is full frame or crop sensor.

[_aavaa_]

Relative size of subject and background is cause by distance to them, not focal length.

[tveyben]

Also called ‘perspective’ and the only way to change it is to move the position of the camera

It does not matter if you crop an image taken with a 50mm lens to get the same area of the motive as taken with a 300mm lens from the same ‘standpoint’ - there will be no difference between foreground and background (except for grain and noise - but that’s another story… ;-)

You have to move the camera to change that.

This is often seen in movies (those shot on real film) as opposed to on video as zoom lenses are often used without moving the camera, film based often use a dolly to move the camera. The effect of combining zoom and camera movement to keep the same crop of the foreground while having a dramatic effect of the background quickly getting larger/closer (or vice versa) is really effective - also in illustrating this concept.

In my early life (before taking the education as a photographer) I was really liking wide angles as it brought ‘life’ in to a lot of pictures. Wide as in 24 mm for my 35mm camera (Nikon F2, from 1973 should you wonder) was a favorite, replacing my 28 mm.

Too bad full frame digital is still so expensive. Using a 14-24 f/4 on the DX format in (Nikon D7100) just is’nt the same.

So now the iPhone is the most used camera (you know - the camera you have with you…!)

[fvgvkujdfbllo]

If you have 50mm lens, try it. It will look exactly same as if you are looking through a tube with a naked eye.

[hk__2]

Both, actually.

[_aavaa_]

It’s entirely independent of focal length.

It has to do with the ratio of the subject-camera distance to the background-camera distance.

As others have pointed out you prove this to yourself in one of two ways:

1. Frame with telephoto, then shoot with a wide angle lens and digitally zoom in photo.

2. Frame with wide angle and then shoot a panorama with the telephone and stich.

2 is significantly harder if you are close to the subject.

[rozab]

Well, no. This article has some clarifications: https://petapixel.com/is-lens-compression-fact-or-fiction/

[Aurornis]

This is a million times easier to demonstrate with images than text. Wikipedia has a good animation: https://en.m.wikipedia.org/wiki/Perspective_distortion

This page doesn’t have any images but covers the concept quite well: https://en.m.wikipedia.org/wiki/Normal_lens

The concept of matching a picture to normal human vision goes back to the age of paintings, before any photography even existed.