Spiney Loc: Reading, PA

I thought I read a long time ago that on a 35mm camera a normal 50mm lens is included because it’s pretty much WYSIWYG (What you see is what you get). But I know this is definitely not true when it comes to objects like the moon. Is it some sort of perspective trick, or because our Eyes and Mind can concentrate on a single object out of a whole seen that to our eyes 👀 the full moon 🌕 looks relatively large. But when shot with anything less than a 2-300mm it’s a very small circle.

I’ve been photographing since the early 70’s and shot professionally for 20 years. I’m also an amateur astronomer. This just came to mind while watching the almost total lunar eclipse last week. Then tonight I watched a video from an accomplished Amateur astronomer & YouTube monitizer who decided to go simple and capture the eclipse on a FX Canon camera with a 110 2.8 lens. The moon 🌚 was pretty small.

So to sum it up ⬆️ is there truth to a 50mm being generally what we see? And what MM on an FX or DX I have DX gives you the moon 🌝 as our eyes 👀/ brain 🧠 perceives it. Thanks 🙏 in advance. Dave in PA.

BTW I do realize there’s a difference especially to our eyes if the moon is at the horizon or at ZENITH.

Alphabravo2020

Part of the answer lies in determining the cutoff for peripheral vision which if included I'm guessing would put the eye at something more like 18mm. But peripheral vision is not acuity based and isn't usually included when I hear people talk about equivalent focal length.

Also the eye moves continually, increasing the effective FOV.

This is mostly above my pay grade but very interesting. I shoot alot of buildings and property and I feel like my 18-300mm almost always matches my eyes at 18mm.

David in Dallas Loc: Dallas, Texas, USA

I think perception is different when only a single object is the focal point (the Moon). When the entire field visible contains something to see, the brain reacts differently, moving the eye to focus on individual elements one at a time.

I have photographed the Moon using a 500mm mirror lens on my DX camera (D7000). It's pretty stiff and hard to focus. Now that I have a 200-500mm zoom I may try some more photos of the Moon. That lens is very good and would probably do very well (and autofocus works with it, too).

hrblaine

AB says 18mm. What about the rest of you? I have no opinion as this is above my pay grade.

If I weren't so lazy, I guess that I could take several pics (12mm, 18, 24, 30, 36, 50, 80, 100 etc. and see if any matched my unaided eye.) Anybody want to do that - or has it been done? Otherwise I'm willing to accept Alphabravo's 18mm. After all, this is not what got me out of bed at 3:00 AM! <g> Harry

flip1948 Loc: Hamden, CT

The 50mm focal length was chosen by the developer of Leica 35mm cameras to be the lens that matched "normal vision". I read long ago that it was actually closer to 58mm.

However, today I read an article about Nikon's new Z 40mm lens where the author claimed that it was the focal length that approximated normal viewing.

I just Googled the subject and found that the "normal" lens focal length should be equivalent to the diagonal of the film frame which would be about 43mm for 35mm film which has a frame that is 36mm by 24mm, the same dimensions as most "full frame" digital sensors.

A normal lens should match the magnification you get when you look through your eyes...not the angle of view. Does your subject look the same size and distance from you when viewed through your eyes and your viewfinder?

That would be considered normal.

I've always found that 50mm comes up a little short when I've tested this by taking my eye away from the viewfinder and used my eyes...so I came to believe that the 58mm focal length might be more accurate.

Try it yourself and see.

Pablo8 Loc: Nottingham UK.

Try looking with one eye... I have Macular Degeneration in my left eye, so the right eye is naturally dominant as to what I see. The camera/ lens is also just a 'Single Eye'. Does that come into the equation as to what focal length is most appropriate?

tradio Loc: Oxford, Ohio

I've always considered it to be a 50.

cmc4214 Loc: S.W. Pennsylvania

Print the picture of the moon large enough to completely fill your field of view and still be able to focus your eyes on it. In other words your printed picture, or (monitor) is no where nearly as large as your field of view

Just Fred Loc: Darwin's Waiting Room

I think the answer these days depends on the image area. Your original question specified the 35mm film size, which I always held was around 52mm, which was typically adjusted to 50mm. But since we've gone digital, the issue becomes sensor size, and the reference is to "35mm equivalent" or "full frame." One now needs to adjust for the "crop factor" to figure out which lens produces the closest to the human eye.

Here's a discussion and some algorithms that might help: https://cameraville.co/blog/2018/26/10/crop-factor-and-field-of-view-what-is-the-35mm-equivalent

Longshadow Loc: Audubon, PA, United States

Yup, on a full frame.

If the subject looks 50 feet away with the eye, the 50mm will have it appear 50 feet away in the image.
Anything else will make it appear closer or farther away.

On my 1.6 crop sensor, it would be about 31mm.

Mac Loc: Pittsburgh, Philadelphia now Hernando Co. Fl.

I agree with 50mm on a full frame camera.
When I first started with photography 50mm lenses were also referred to as normal lenses.

jim quist Loc: Missouri

50mm on a full frame camera is what your eye perceives

R.G. Loc: Scotland

The human eye can be thought of as being like a very wide angle lens with a small sweet spot. Outside of the sweet spot the focus, detail perception, colour perception and contrast perception are poor. The sweet spot provides an angle of view roughly the same as a FF focal length somewhere between 40mm and 60mm - it varies from person to person. As David pointed out, within that sweet spot we can concentrate on specific areas, so while our eyes can't zoom, our attention can zoom in to focus on quite small areas. The effect would be exaggerated if we tried to focus on specific details on the moon.

As flip1948 pointed out, we should go by what provides the same size and distance perception as our unaided eyes. The trouble is, that will change depending on how focused our attention is. We don't go around in a permanent state of focusing our attention on distant details, so maybe we should go by what things looks like when we're in landscape mode rather than star-spotting mode.

Longshadow Loc: Audubon, PA, United States

Paying more attention (focusing on distant details) on a tree far away does not make it appear closer. Still the same relative distance. Only the focus point changes.

And that would be a 50mm lens on a full frame camera.

R.G. Loc: Scotland

The OP has pointed out that if you photograph the moon with a 110mm lens (much more zoomed in than 50mm) you get a tiny circle in the frame that looks much smaller than how you see it with your eyes. My guess is that if he was photographing a wider scene like a cityscape or landscape with the moon as just a small part of it he wouldn't be saying that, but he was photographing the moon specifically (which I suspect means the moon plus a lot of featureless sky).