your eyes

[3bayjunkie]

Have any of you ever wondered what your eyes 35mm equivalent is as far as maximum aperture, shutter speed and field of view?

I was thinking about it the other day, And I think they are about equivalent to a 70mm lens, but could be off by some mm's not sure the exact size it would be.

[Bruce A]

I always thought is was about 50mm, but I accept I could easily be wrong. I know when I use a slow shutter speed on my eyes, I tend to skip a few frames

Also, each of my eyes has a different aperture I'm afraid

[IABoomer]

Of course, the standard disclaimer about double-checking the validity of Wiki data applies.

https://secure.wikimedia.org/wikiped...#Dynamic_range

Dynamic range

The retina has a static contrast ratio of around 100:1 (about 6½ f-stops). As soon as the eye moves (saccades) it re-adjusts its exposure both chemically and geometrically by adjusting the iris which regulates the size of the pupil. Initial dark adaptation takes place in approximately four seconds of profound, uninterrupted darkness; full adaptation through adjustments in retinal chemistry (the Purkinje effect) are mostly complete in thirty minutes. Hence, a dynamic contrast ratio of about 1,000,000:1 (about 20 f-stops) is possible.[3] The process is nonlinear and multifaceted, so an interruption by light merely starts the adaptation process over again. Full adaptation is dependent on good blood flow; thus dark adaptation may be hampered by poor circulation, and vasoconstrictors like alcohol or tobacco.[citation needed]

The eye includes a lens not dissimilar to lenses found in optical instruments such as cameras and the same principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm (f/8.3) in a brightly lit place to 8 mm (f/2.1) in the dark. The latter value decreases slowly with age, older people's eyes sometimes dilate to not more than 5-6mm.[citation needed]
[edit] Field of view

The approximate field of view of a human eye is 95° out, 75° down, 60° in, 60° up.[clarification needed] About 12–15° temporal and 1.5° below the horizontal is the optic nerve or blind spot which is roughly 7.5° high and 5.5° wide.[4]

The "field of view" numbers quoted look more like angle of eye rotation in the socket than field of vision covered. I suppose when you consider the way our eyes rapidly move to take in a scene, you're probably looking at something like an 8-50mm zoom lens, where we can see a vast amount of light from the sides, but we "zoom" in on specific items to focus on.

[nickbedford]

If the retina has a static contrast ratio of ~6.5 stops, why can I see many more stops in a single scene than my camera can even wish for?

[Bruce A]

Great info - alas we have no macro.

[3bayjunkie]

Originally Posted by IABoomer

Of course, the standard disclaimer about double-checking the validity of Wiki data applies.

https://secure.wikimedia.org/wikiped...#Dynamic_range



The "field of view" numbers quoted look more like angle of eye rotation in the socket than field of vision covered. I suppose when you consider the way our eyes rapidly move to take in a scene, you're probably looking at something like an 8-50mm zoom lens, where we can see a vast amount of light from the sides, but we "zoom" in on specific items to focus on.

interesting. however the lens size comparison i was doing was while looking through a 70-300mm lens on my film camera. the 70mm side if i put my eye up to it looked very close to what i see normally in regard to size. however we have more periferral vision than a 70mm lens.

[SwissJon]

Ah.. What you're talking about is magnification..

It's generally accepted, I think, that a 50mm lens replicates the magnification and perspective encountered by our eyes. On a crop sensor a 35mm lens gives a similar field of view, on an FX sensor, the 50 mm gives this..

Some eye pieces magnify the image, either making it smaller or larger, so a 70mm lens may give this appearance on your camera, but not on someone elses.. This makes little difference to the outcome, since the added magnification is in the eyepiece, not the lens.. It's perfectly possible that your camera gives the impression of similar sized image at 70 ish mm and someone else's has no magnification, and gets the same result at 50mm.

[ravncat]

Originally Posted by SwissJon

Ah.. What you're talking about is magnification..

It's generally accepted, I think, that a 50mm lens replicates the magnification and perspective encountered by our eyes. On a crop sensor a 35mm lens gives a similar field of view, on an FX sensor, the 50 mm gives this..

Not so much - I've heard that referenced, but I can't seem to find anything to really support that other than lots of people "referencing" it. I suspect, if the 50mm has anything to do with the actual eye - it's likely the area that we "focus on"

The reality is we've got the peripheral thing and two eyes that are merging vision in addition to the different magnification - there just isn't a lens for it I think I recall that 70mm looks about the same magnification (on crop sensor) as my eye - but a much much wider lens was closer to my field of view. Our brains probably do some really cool stuff with the input image data.

As far as I can tell, the reason 50mm is called "normal" has everything to do with the sensor diagonal, a normal lens by definition is one that has a focal length equal to the diagonal of the sensor. This appears to be the simplest to design as well. The actual normal for 35mm is like a 43mm lens.

The reason that they "look" normal, is because they are were among the first camera lenses and are extremely common - our visual libraries know the look of the "normal" lens - and we accept it as normal.

[SwissJon]

The viewfinder on a D700 is 0.72x so that you can see 95% of the picture through the viewfinder (If you didn't, you'd need a much larger viewfinder, or you'd only see much less of the picture). 70x0.72=50.4. This means that a 70mm lens appears to have the same size as a 50mm lens at 1x magnification.. So if the argument is that at 70mm the view through the viewfinder is approximately the same as the human eye perceives it to be, not including FoV, (this can be confirmed by doing it, putting your eye to the view finder at 70mm and opening your other eye so you can see two versions of the same image as described by the OP) then this confirms the theory that 50mm approximates human sight.

Of course, we all have slightly different vision, depending on a lot of factors, so it's only an approximation.. But if you take into account the viewfinder magnification, you can work out what mm your eye equates to fairly easily..

Of course, if you print out something poster sized that you've taken on a crop sensor, this theory is thrown off balance.. But there is a perfect distance for viewing all pictures, based on when the photo looks approximately the same as you experience in real life.. But for general use, you can work it out for yourself by experiment.. You don't need Wikipedia to tell you something..

[ravncat]

don't forget the 1.5x from the crop camera- I found 70 about right on my d70. which is more like a 105 on a d700...