Focal length of the eye? I've always understood 50 - 55mm to be a lens size that correlates most closely to the human eye. I was out this morning trying to get a particular view...

John N Loc: HP14 3QF Stokenchurch, UK

I've always understood 50 - 55mm to be a lens size that correlates most closely to the human eye.

I was out this morning trying to get a particular view (unsuccessfully) using my 400mm prime lens. I noticed that the compression was considerably more when viewed through my 8x 42 binoculars.

Any thoughts?

ejones0310 Loc: Tulsa, OK

John N wrote:

I've always understood 50 - 55mm to be a lens size that correlates most closely to the human eye.

I was out this morning trying to get a particular view (unsuccessfully) using my 400mm prime lens. I noticed that the compression was considerably more when viewed through my 8x 42 binoculars.

Any thoughts?

It depends on the sensor size. “Normal” for the human eye is about 17mm. But normal for a camera depends on the sensor size. “Normal for a full frame or 35mm film camera I
Is about 50mm. For an APSC camera it’s about 30mm. It all depends on the diagonal length of the sensor size.

Look at this article for a quick explain of the calculations.

https://shuttermuse.com/calculate-cameras-crop-factor/

On your binoculars, the field of view varies from model to model even though they are all 8x. The field of view is probably what is throwing you off.

John N Loc: HP14 3QF Stokenchurch, UK

I should have made it clear that I was using a full frame sensor and I've believed this since OM2 days. The binoculars are a good mid range pair but the f.o.v. might well be the answer.

However, if anyone else a point of view I'm open to hear it.

GoofyNewfie Loc: Kansas City

I googled it, and the answer varies (and some say so does the eye)
I’ve seen 17 up to 24mm.

This one lists several sources:
https://hypertextbook.com/facts/2002/JuliaKhutoretskaya.shtml

Here’s one from Cambridge in Color:
Unfortunately our eyes aren't as straightforward. Although the human eye has a focal length of approximately 22 mm, this is misleading because (i) the back of our eyes are curved, (ii) the periphery of our visual field contains progressively less detail than the center, and (iii) the scene we perceive is the combined result of both eyes.

https://www.cambridgeincolour.com/tutorials/cameras-vs-human-eye.htm

John N Loc: HP14 3QF Stokenchurch, UK

Thanks, I keep forgetting these people. I've signed up for updates now so hopefully I'll not forget them again.

JD750 Loc: SoCal

I think it's more about field of view than focal length. I have heard that a 50mm lens on a "full frame", i.e, 35mm film frame size sensor, will yield a similar field of view as the human eye. But that is an average, and the exact value will vary from human to human. I have no idea what the variance is. And camera viewfinders don't always show exactly what is captured in the frame so keep that in mind too.

I just tried looking in the lens then looking at the scene using my Nikon Z. A zoom lens is good for this experiment. Note one eye vs both eyes yields different results. I used both eyes. What i find is my eyes are quite wide, I can see things on the periphery. Maybe closer to 17mm as said above. But the "main" field of view for my eyes looks to be about 50mm for me. Your mileage will vary. Try it with your camera and report back here.

a6k Loc: Detroit & Sanibel

Try looking through the camera's VF with one eye and the binocs with the other eye and pay attention only to image size, not field of view.

CHG_CANON Loc: the Windy City

Blue eyes tend to see wider, like 42mm while brown eyes are closer to 48mm. 50mm is a good general estimate.

dennisallard Loc: Southern Maine

Many years ago I attended the Nikon School of Photography when it came to Boston. I remember them teaching us that the focal length that matches what you see with the naked eye is the diagonal of the image on the film. For 35mm film, or a full frame sensor, that would be 42mm. For a crop sensor - 28mm.

Architect1776 Loc: In my mind

JD750 wrote:

I think it's more about field of view than focal l... (show quote)

The eye sees differently depending on the situation. Actually you brain is seeing differently. You can focus in stress situations only on the source of stress and "see" nothing else, 10 degrees perhaps at most. Of just sit in your living room and "see" almost a full 180 degrees when relaxed.
Some people get focused on one thing or another and also see very little around them and have no situational awareness while others with good situational awareness "see" very wide.

WJShaheen Loc: Gold Canyon, AZ

John N wrote:

I've always understood 50 - 55mm to be a lens size that correlates most closely to the human eye.

I was out this morning trying to get a particular view (unsuccessfully) using my 400mm prime lens. I noticed that the compression was considerably more when viewed through my 8x 42 binoculars.

Any thoughts?

Noting the 50-55mm lens size you refer to is the focal length, whereas for the binoculars the 42mm is the aperture.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

John N wrote:

I've always understood 50 - 55mm to be a lens size that correlates most closely to the human eye.

I was out this morning trying to get a particular view (unsuccessfully) using my 400mm prime lens. I noticed that the compression was considerably more when viewed through my 8x 42 binoculars.

Any thoughts?

That concept is little understood. With both eyes open, you field of view is more 35 mm than 50-55 mm. So, a normal lens for 35 mm photography has always been, for Leica, a 35 mm lens, cause that's what the diagonal is in 35 mm film. I think Leica understood.

Architect1776 Loc: In my mind

billnikon wrote:

That concept is little understood. With both eyes open, you field of view is more 35 mm than 50-55 mm. So, a normal lens for 35 mm photography has always been, for Leica, a 35 mm lens, cause that's what the diagonal is in 35 mm film. I think Leica understood.

I am looking at 2 book cases 180 degrees apart, that is wider than 35mm on a ff sensor.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Architect1776 wrote:

I am looking at 2 book cases 180 degrees apart, that is wider than 35mm on a ff sensor.

Good for you, you must have great peripheral vision. You my friend, are special.

Architect1776 Loc: In my mind

billnikon wrote:

Good for you, you must have great peripheral vision. You my friend, are special.

Unless you have a problem with your vision most everyone sees this way. As I carefully explained earlier, people are mentally focused in a narrow field of view today because there is a condition white most live in.
Put a naked girl in front of a guy and he will only see t & p and could not tell what her face looks like.