There's something about the 50mm FOV...

[Bruin]

I work in traffic engineering, and one of our agency's design guidelines is that whenever a traffic signal is placed outside of a driver's "cone of vision," it should be upgraded to a larger size. I checked the federal highway design manuals and they have similar recommendations for road signs as well. This comes from some research done on human vision:

The region of the central retina where a fixated image falls is called the fovea. The fovea has only cones for visual receptors and is about 1.5 to 2° in diameter. Beyond 2°, cone density rapidly declines reaching a stable low point at about 10°. Conversely, rod density rapidly increases beyond 2° and reaches a maximum at about 18° before dropping off (Boff, Kaufman, and Thomas 1986). From 18° outward toward the nose and ears, forehead, and chin, the number of rods decreases but still continues to be higher than the number of cones. Functional detail vision extends to about 10°, worsening in the near periphery from about 10 to 18° and significantly deteriorating in the far periphery from about 18 to 100°. [emphasis mine]

In practice we use a "cone of vision" 40° horizontally and 30° vertically, which happens to be a close match to the 50mm FOV (40°/27°). Interesting stuff.

 

[Roger Hicks]

I work in traffic engineering, and one of our agency's design guidelines is that whenever a traffic signal is placed outside of a driver's "cone of vision," it should be upgraded to a larger size. I checked the federal highway design manuals and they have similar recommendations for road signs as well. This comes from some research done on human vision:

In practice we use a "cone of vision" 40° horizontally and 30° vertically, which happens to be a close match to the 50mm FOV (40°/27°). Interesting stuff.

Dear Kevin,

Interesting, but highly disputable. How do you rate the relative priorities of sabre-tooth tigers and traffic signals?

Cheers,

R.

 

[Rob-F]

Dear Kevin,

Interesting, but highly disputable. How do you rate the relative priorities of sabre-tooth tigers and traffic signals?

Cheers,

R.

Hi Roger, do you want to elaborate a bit on that thought? I think you are thinking of the hereditary adaptive value of peripheral vision in saving us from, well, sabre-tooth tigers; is there a need to prioritize this?

 

[Bruin]

Hi Roger,

What do you find highly disputable? When you want to pick up details with your eyes, you look right at something or up to 10° away. Deviate more than 18° and your ability to see detail drops off fast. That's simply how our eyes work.

 

[Rob-F]

Roger has probably gone to bed. It must be 1 or 2 AM by now for him. I guess he'll catch up with us later. One of the functions of peripheral vision, of course, is to alert us to anything entering the field of vision: it could be a dangerous animal or a traffic light. It seems to me that both have a high priority, only in a different context. I'm sure Roger's answer will be interesting, once he gets a chance to talk more about his thoughts.

 

[zauhar]

I think that peripheral vision responds more to changes (motion) than in details - exactly like a saber-tooth tiger picking you out as its next meal. It is a more primitive part of the visual system. ( I am reaching way back to a grad course in neurophysiology.)

The correspondence that Roger points out is really interesting, in my opinion. I frequently see 50mm mentioned as the single-best focal length, and I guess in my experience I would agree - it does correspond to your central field of vision.

Randy

 

[Keith]

I remember reading an article about some controlled tests they did with top level race car drivers. Without exception they all had peripheral vision that was way above average, especially in their ability te perceive actual detail in this zone.

 

[Bob Michaels]

Personally, I want a lens field of view that makes the best looking photos on paper.

I believe how my eyes work in real life has very little bearing on this.

 

[Rob-F]

Personally, I want a lens field of view that makes the best looking photos on paper.

I believe how my eyes work in real life has very little bearing on this.

Yes! Sounds right! One scans a photo, rather than taking it in at one glance. So the lens field of view does not need to match that of the eye, to make an effective or convincing photo.

 

[Bob Michaels]

Yes! Sounds right! One scans a photo, rather than taking it in at one glance. So the lens field of view does not need to match that of the eye, to make an effective or convincing photo.

Actually Rodger's comment "How do you rate the relative priorities of sabre-tooth tigers and traffic signals?" said the same thing. In simple terms, they are unrelated.

 

[Keith]

I guess it has some relevence for the hip shooters who use a 50mm lens!

I could have sworn I actually saw a sabre tooth tiger out of the corner of my eye the other day. It turned out to be a traffic signal. 😀

 

[paulfish4570]

our peripheral vision is at its best when picking up motion; when motion is picked up, we turn our central vision that way. we are predators, after all. what this has to do with photography, i am not sure. but it is very helpful when hunting ... 🙂

 

[Bruin]

I'm not saying peripheral vision is any less important, or assigning priority of central vs. peripheral.

When you stop scanning and look at something, 50mm captures most of the detail that your eyes pick up. Of course how much time the eyes spend scanning varies widely from person to person, and changes depending on what you're doing (staring at a computer screen, walking down the street, etc.)

Maybe for your style of taking pictures this has no bearing because you actively scan and see the world in a wider FOV. But for those who rely more on their central vision, 50mm has some correlation to how your eyes work.

 

[rogerzilla]

Some of mny best pictures are taken with a 50mm. It's because the lens adds no perspective effect; you have to work harder at the composition. With a 21mm or a 135mm, the temptation is to use DOF or perspective for a "dramatic" shot which ends up looking a bit cliched.

 

[Thomas78]

Thank you for this interesting discussion!

In my experience I think that the 50 mm lens (which ist more a 52 mm lens in most cases for rangefinder) is a bit narrower that my normal FOV.

In MF "normal lenses" are about the same focal lenght as the diagonal of the film (75 or 80 mm for 6x6 (diagonal is 79.2 mm, 105 mm for 6x9 (diagonal is 102.6).
The diagonal of 24x36 mm is 43.3 mm which is quite far away from 50 or even 52 mm.

This supports my opinion, that 40 mm could perhaps be a more versatile normal lens - at least for me.

 

[steelheart]

My two favorite focal lengths for 35mm RF photography are 28mm and 50mm. The 35m is also nice but is very close to the 28.

If I had to pick between 28mm and 35mm, I think I'd go with 28mm. As for the 50, it almost seems like a short tele to me because I've shot with my 28 so much.

You can cover alot of photographic territory with a 50mm and either a 28 or 35.

 

[M4cr0s]

Interesting topic!

I got an eye condition that leads to the loss of peripheral vision and night blindness (the rods "die") and I've got about 7 degrees worth of vision on each eye, which then again, since it's overlapping I guess, translates into perhaps 10-12 degrees total. Just for the record, the rule of thumb seems to be that healthy individuals should be able to at least detect movement and shapes at the outer edges of their peripheral vision, something that translates to a fov of about 180 degrees.

I really like a nifty-fifty, but in reality something like a 70-80mm lens is closer to what I see with my own eyes (I find the CV 58 1.4 or a 60mm macro on a crop sensor camera is just a tiny bit too tight). Looking through a viewfinder or on a LCD using a wide-angle can actually be an aid for me, since the coverage of say a 20mm lens is many times what I see with my naked eyes. Also since digital sensors in combination with LCD's tends to make scenes appear much brighter than they are, I can also see stuff in dark conditions that I can't with the naked eye due to night blindness.

Perspectives are indeed different 😀

Mac