Is a 40mm lens the sweet spot?

[ampguy]

depends

depends

on where the point(s) of focus the eye is at, and how much peripheral vision you want to include in the definition of "field of view"

FWIW, I have read books and studies that cite 35mm, to 105mm, the most common 50mm, but to me, the most compelling, 43mm.

what is the field of view of the average human?

 

[Doug]

To return to what a former poster brought up - from where originates the notion that a focal length corresponding to the frame diagonal is "normal"?

It might be useful to work back from the end result: A print on display. Let's suppose a gallery show... The theory has it that the "best" viewing distance for a print is when the eye's angle of view matches the angle of the lens making the image, adjusted for any cropping. So, you'd stand closer to a wide-angle shot than a telephoto shot. For a print made with a 28mm lens on 35mm film, for instance, you would move in so that the corners form a 75° angle with the eye. For a print made with an 85mm lens on 35mm film, you would stand back so that the corners form a 28° angle with the eye.

This would give the most "natural" viewing perspective, and some print makers size their prints to encourage this, and it may be kept in mind in hanging the show. For instance, a largish wide-angle print hung in a place where the viewer cannot back away, encouraging the "proper" distance.

So why would viewers need to be influenced or forced into the appropriate viewing distance? Because of another factor, now zeroing in on the question at hand...

It turns out that for most people with normal eyesight, the most comfortable viewing for a rectangular flat artwork is from a distance about equal to the object's diagonal. So people tend to position themselves (or hold the item) accordingly.

Using a trigonometric approach, imagine a triangle where the distance from one apex to the opposite side is equal to the length of that opposite side. Bisect the triangle along that distance line. Now to figure the angle at that new apex for which the sine is half the cosine... That's about 26.5°... since the triangle was bisected we need to double that angle to know the original angle of the apex: 53°. Well well, that's the angle of view of a 43mm lens on 24x36mm frame, for which the diagonal is 43mm.

Going at it from the optical approach: The definition of focal length is the distance from the lens's optical center to the film/media/sensor. So if the lens focal length is the same as the media diagonal, that matches the most natural viewing relationship later between eye and print.

 

[back alley]

so a 28 on the rd1 gives the fov of a 43mm lens, thus it's the 'normal' lens for the rd1?

 

[Prosaic]

Suddenly I hear more and more about the 40mm lens is the sweet spot and 50mm became the standard via an accident by Barnack in the 30's. My typical kit has been 21-40-90, although I am sneaking in the 75mm more and more. Others's thoughts? I almost consider 50mm as a very short tele these days.

40mm lens:

40 or 50 or 60, these are just numbers. I am getting better results the longer I use one lens exclusively, regardless of focal length. After a week, maybe after a month, you´ll see how versatile a 21mm lens really is. 😀

 

[Prosaic]

I have an arsenal of Nikon F/F2/FM2/FM3A and 22 lenses

Wow, I wonder why some photographers gather that lot of equipment, most of which they probably never touch for years. Owning less lenses makes it far easier to pick one for a walk.

 

[Karefin]

It might be useful to work back from the end result: A print on display. Let's suppose a gallery show... The theory has it that the "best" viewing distance for a print is when the eye's angle of view matches the angle of the lens making the image, adjusted for any cropping. So, you'd stand closer to a wide-angle shot than a telephoto shot. For a print made with a 28mm lens on 35mm film, for instance, you would move in so that the corners form a 75° angle with the eye. For a print made with an 85mm lens on 35mm film, you would stand back so that the corners form a 28° angle with the eye.

This would give the most "natural" viewing perspective, and some print makers size their prints to encourage this, and it may be kept in mind in hanging the show. For instance, a largish wide-angle print hung in a place where the viewer cannot back away, encouraging the "proper" distance.

So why would viewers need to be influenced or forced into the appropriate viewing distance? Because of another factor, now zeroing in on the question at hand...

It turns out that for most people with normal eyesight, the most comfortable viewing for a rectangular flat artwork is from a distance about equal to the object's diagonal. So people tend to position themselves (or hold the item) accordingly.

Using a trigonometric approach, imagine a triangle where the distance from one apex to the opposite side is equal to the length of that opposite side. Bisect the triangle along that distance line. Now to figure the angle at that new apex for which the sine is half the cosine... That's about 26.5°... since the triangle was bisected we need to double that angle to know the original angle of the apex: 53°. Well well, that's the angle of view of a 43mm lens on 24x36mm frame, for which the diagonal is 43mm.

Going at it from the optical approach: The definition of focal length is the distance from the lens's optical center to the film/media/sensor. So if the lens focal length is the same as the media diagonal, that matches the most natural viewing relationship later between eye and print.

Thank you, Doug! Now I'm getting a hang of it... When you have a field of view which you don't have to crop or expand at all; you have in your view what you need to see, nothing more, nothing less - that's "natural", because you can't zoom with your eyes.

And the analogy for the lens "viewing at the picture" so that it is most natural for it, was very enlightening.

Now we all can imagine the framelines of a 40-45 mm to our fields of vision, plus some tele, some wide-angle ones too...

 

[George Bonanno]

An image from a 45mm lens projected on 35mm film using a full frame still camera is the perfect complement to human vision. Any other focal length is a distortion of reality.

"Contort Yourself"... James Chance

 

[Kent]

Yes, 40mm are great with RF cams and with my DSLR (1.6crop) I love the 24mm lenses (~ 38.6mm) - I wonder why. 😉

 

[ampguy]

sort of

sort of

The fov of 43mm would be close to what I consider a "normal" view. But if you open your other eye, and look forward in the same direction with both ones, one in VF with 43mm fov, you'll notice that you're cutting off peripheral vision.

But from a lens, distortion, compression perspective, the 28mm has more of it than a 43mm, or even a great 35mm. I've always liked the fov of a 40 on the RD1, and while seemingly a tighter than "normal" fov, it has less distortion than a wide 28 (for example, look through the rf with 28 while standing, and rotate the camera from the ground to different angles, and you'll see distortions that your other eye won't, as your brain corrects for it.

A side note, since you're using the RD1, is that a 40 fits the 35mm framelines very well, probably better than a 35 at many subject distances.

so a 28 on the rd1 gives the fov of a 43mm lens, thus it's the 'normal' lens for the rd1?

 

[ampguy]

interesting

interesting

but unrealistic. I look at gallery photos from a few feet away, prints in books about 12" away. Images on monitors about 12-18" away. That isn't going to change.

It might be useful to work back from the end result: A print on display. Let's suppose a gallery show... The theory has it that the "best" viewing distance for a print is when the eye's angle of view matches the angle of the lens making the image, adjusted for any cropping. So, you'd stand closer to a wide-angle shot than a telephoto shot. For a print made with a 28mm lens on 35mm film, for instance, you would move in so that the corners form a 75° angle with the eye. For a print made with an 85mm lens on 35mm film, you would stand back so that the corners form a 28° angle with the eye.

This would give the most "natural" viewing perspective, and some print makers size their prints to encourage this, and it may be kept in mind in hanging the show. For instance, a largish wide-angle print hung in a place where the viewer cannot back away, encouraging the "proper" distance.

So why would viewers need to be influenced or forced into the appropriate viewing distance? Because of another factor, now zeroing in on the question at hand...

It turns out that for most people with normal eyesight, the most comfortable viewing for a rectangular flat artwork is from a distance about equal to the object's diagonal. So people tend to position themselves (or hold the item) accordingly.

Using a trigonometric approach, imagine a triangle where the distance from one apex to the opposite side is equal to the length of that opposite side. Bisect the triangle along that distance line. Now to figure the angle at that new apex for which the sine is half the cosine... That's about 26.5°... since the triangle was bisected we need to double that angle to know the original angle of the apex: 53°. Well well, that's the angle of view of a 43mm lens on 24x36mm frame, for which the diagonal is 43mm.

Going at it from the optical approach: The definition of focal length is the distance from the lens's optical center to the film/media/sensor. So if the lens focal length is the same as the media diagonal, that matches the most natural viewing relationship later between eye and print.