Human Eye Focal Length

[boojum]

I guess I do not have to tell you that I am not the sharpest knife on the tree. And I have to resort to some pretty primitive methods to understand things. The simpler the better. So I fired up a camera with a lens equivalent to a 43mm on a 35mm camera and I had pretty near binocular vision in what could see through the camera. Not perfect but pretty close. This substantiates for me that what the fellow, wolfcrow, said in his YT video is pretty close to the mark. I think he, too, said it was close to the mark, not perfect. I do not think that looking at an image taken will be as accurate and simple a way of testing this as the image for each eyes is not there when looking at the captured image. Add 98 cents and you have a dollar. ;o)

 

[lynnb]

Don't humans "see via their brains"? The "sensor" is in our brain. Right?
Do we all have identical brain sensors?
Hm.

Our brain sensor relies heavily on memory. I wouldn’t say everyone’s memory- both working and long term- is identical. What we see is a brain interpretation and reconstruction of a continuous scanning process, with the current point in time focus of attention the most accurate part of the “image”.

 

[Out to Lunch]

Seeing is a wonderfully complex process: we all have noses sticking into our field of view, but our brains ignore it, so we don't 'see' it.

 

[Coldkennels]

I guess I do not have to tell you that I am not the sharpest knife on the tree. And I have to resort to some pretty primitive methods to understand things. The simpler the better. So I fired up a camera with a lens equivalent to a 43mm on a 35mm camera and I had pretty near binocular vision in what could see through the camera. Not perfect but pretty close.

...maybe I'm misunderstanding what you're saying, but if you're talking about looking through a lens via an SLR viewfinder or EVF and keeping the other eye open, this is going to depend entirely on the magnification of the viewfinder.

After all, I can perform this same feat with both SBOOI and SEROO external viewfinders... and one of them is for 50mm and the other is for 90mm.

One thing that might be of interest/relevance to this conversation is a video I watched the other day about the switch from 4:3 to 16:9 screens:

In it, there's a section where he describes how Paramount Pictures defined the format of the natural human field of view as 1.85:1... based on holding out your hands horizontally and vertically at the periphery of your vision and measuring the distance. Those dimensions work out to a frame a little longer than a 16:9 widescreen image, but also a fair bit taller than a Horizon panoramic.

 

[joe bosak]

There's what we are visually or consciously aware of - so if something moves you notice. Wide, ultrawide, probably very oblong.
There's what you can focus intently on. More like telephoto.
In between there's what you might call your field of attention, which depends on context (what you are looking at, eyes don't stay still). Quite wide through normal to short telephoto.

That's why some of us like big photos with everything in focus, so our eyes can rove around, like in reality.

 

[raid]

Our brain sensor relies heavily on memory. I wouldn’t say everyone’s memory- both working and long term- is identical. What we see is a brain interpretation and reconstruction of a continuous scanning process, with the current point in time focus of attention the most accurate part of the “image”.

I agree with you that we don't all have identical memories and then different sensors in our brains. This should have an impact on how we like/prefer certain lens focal lengths.

 

[boojum]

...maybe I'm misunderstanding what you're saying, but if you're talking about looking through a lens via an SLR viewfinder or EVF and keeping the other eye open, this is going to depend entirely on the magnification of the viewfinder.

After all, I can perform this same feat with both SBOOI and SEROO external viewfinders... and one of them is for 50mm and the other is for 90mm.

One thing that might be of interest/relevance to this conversation is a video I watched the other day about the switch from 4:3 to 16:9 screens:

In it, there's a section where he describes how Paramount Pictures defined the format of the natural human field of view as 1.85:1... based on holding out your hands horizontally and vertically at the periphery of your vision and measuring the distance. Those dimensions work out to a frame a little longer than a 16:9 widescreen image, but also a fair bit taller than a Horizon panoramic.

True, EVF magnification makes a difference. I had not factored that in. It is a convenience that it works out this way. As for field of view, that wide Paramount-defined field of view may be correct. I had been shooting some recently in that format. It fills the computer screen perfectly. But it takes away the top and bottom of what I normally would have so can be achieved through post edits. 4 x 3 works fine and covers the most territory. Which brings me to that part of 16:9, magnification within that field of view. If I use my EVF at 16:9 with a lens equivalent to a 35mm 43mm lens I still get what seems to be binocular vision. I am just looking through a different window while getting it.

 

[DownUnder]

Yet another video to go on my TBWS (to be watched someday) list. If I live long enough. In this household, cat videos get top priority.

As far as camera lenses go, I harken to The Nifty Fifty.

But it's a lens I find boring, and almost never use, even tho I have two Nikon 50/1.4s and they are among the best optics Nikon ever made... I'm either a '28 or an ' photographer, and my '50s will eventually go to some lucky buyer from my estate.

Yet on the rare occasion that I use one of my '50s, I am always amazed at the quality of the images it makes. Sharp as anything. Everything nicely in balance. Depth of field can be an issue, but I usually plan for that when I make the photo, so it's no great issue.

Yet I still dislike this focal length - 50. "Standard". Like "normal" which to me equates to "chemically inert" = boring.

For me this is one of life's many conundrums, this.

 

[wes loder]

50mm is "normal" for 24x36 is because of the "normal" perspective that it gives. To explain: If you shoot a scene with a 50mm lens, take that negative you shot and make a 5x7 or 7.5x11 print, then hold that print up at "normal" viewing distance (about one foot for a 5x7, or close to nineteen inches for a 7.5x11 print), you should find that the scene and the print's perspective will be approximately the same. It has nothing to do with the angle of view of the human eye, or the diagonal of the film frame. Now, if you prefer the different perspective that a wide-angle lens or a telephoto lens gives, that's fine, but it will not be a 'normal' perspective. I did most of my shooting with a 400mm lens on 35 for years. Liked the ability of the lens to select and isolate, but that did not make it a "normal" any more than using a 21, 28 or 35. We each have our preferences. As to why so many amateur 35mm cameras came 45, 43 or 42mm lenses. More forgiving, more depth of field.

 

[agentlossing]

50mm is hardly boring to me. It's really a slightly telephoto focal length, with very straight lines and some subject compression. 40mm is closer to a true normal lens and is also more basic in my eyes. I use 40mm a ton but it's partly because of how neutral it is - it imparts no character on the scene of itself. 50mm imparts a pictorial flavor that feels composed and sophisticated.

 

[boojum]

This is a problem, 50mm vs 40mm. The 50 is the traditional "normal" lens and has a lot of choices within its range. And there are sleepers. The KMZ Jupiter 8's can be quite nice. And there are the Zeiss and Leitz and CV has some great glass. The selection of 40's is not so great. Perhaps it is because I am so used to the 50's that I do not find them unrealistic. I should shoot more with the CV 40 that I have. Just to see. ;o) So I just replaced a 35 with the CV 40mm f/1.2 just to see how I like it. Decisions, decisions, decisions.

 

[ellisson]

My parents were rabbits, and I inherited a 270 degree field of vision. It made for weird bedtimes because my mom or dad would read my sister (Bunny) and me (Jack Jr.) two different stories at the same time, each of us holding a book on either side of them. Hearing two stories each night, I developed my love of books. On the downside, we rarely (or rearly) could get away with mischief. Difficult getting out of their field of vision. Probably explains my love of wide angle lenses.

 

[Retro-Grouch]

My parents were rabbits, and I inherited a 270 degree field of vision. It made for weird bedtimes because my mom or dad would read my sister (Bunny) and me (Jack Jr.) two different stories at the same time, each of us holding a book on either side of them. Hearing two stories each night, I developed my love of books. On the downside, we rarely (or rearly) could get away with mischief. Difficult getting out of their field of vision. Probably explains my love of wide angle lenses.

 

[TenEleven]

50mm is "normal" for 24x36 is because of the "normal" perspective that it gives. To explain: If you shoot a scene with a 50mm lens, take that negative you shot and make a 5x7 or 7.5x11 print, then hold that print up at "normal" viewing distance (about one foot for a 5x7, or close to nineteen inches for a 7.5x11 print), you should find that the scene and the print's perspective will be approximately the same. It has nothing to do with the angle of view of the human eye, or the diagonal of the film frame. Now, if you prefer the different perspective that a wide-angle lens or a telephoto lens gives, that's fine, but it will not be a 'normal' perspective. I did most of my shooting with a 400mm lens on 35 for years. Liked the ability of the lens to select and isolate, but that did not make it a "normal" any more than using a 21, 28 or 35. We each have our preferences. As to why so many amateur 35mm cameras came 45, 43 or 42mm lenses. More forgiving, more depth of field.

Adding to what wes said, it is noteworthy that these cameras and focal lengths (around 40mm) gained popularity when automated photo-finishers and labs proliferated with the widespread adaptation of consumer color film.

Thus, in the the process of developing the film, and printing the negatives using varying degrees of automation (more as time went on) the negative is almost invariably cropped. Usually it was cropped twice: once during image acquisition to help hide variances in frame positioning and size (and to reduce the need for manual re-positioning of each frame, speeding the process) - and then it was cropped a tiny bit again when the print was put on the photographic paper in order to get a full bleed print. This of course meant that the final result of the print would have been quite close to what people were used to seeing from their "old fashioned" do-it-by-hand photo finishers and using 50mm focal length lenses.

 

[boojum]

50mm is "normal" for 24x36 is because of the "normal" perspective that it gives. To explain: If you shoot a scene with a 50mm lens, take that negative you shot and make a 5x7 or 7.5x11 print, then hold that print up at "normal" viewing distance (about one foot for a 5x7, or close to nineteen inches for a 7.5x11 print), you should find that the scene and the print's perspective will be approximately the same. It has nothing to do with the angle of view of the human eye, or the diagonal of the film frame. Now, if you prefer the different perspective that a wide-angle lens or a telephoto lens gives, that's fine, but it will not be a 'normal' perspective. I did most of my shooting with a 400mm lens on 35 for years. Liked the ability of the lens to select and isolate, but that did not make it a "normal" any more than using a 21, 28 or 35. We each have our preferences. As to why so many amateur 35mm cameras came 45, 43 or 42mm lenses. More forgiving, more depth of field.

I am sorry but I am completely lost in you use of "normal" in this post. It seems to be applied in a manner that it has a few different meanings. I know there is a "normal" setting on my washing machine but how you are using it has me lost. And do you mean 7.5 x 11 or 8.5 x 11?

 

[olakiril]

The actual FL of the eye is pretty wide ~20mm.

The attentional FL (attentional field), or the part visual field that we tend to focus on is usually longer but it varies according to the behavioral needs. You can easily "adapt" the attentional FL, so if you keep using a 35mm lens on a FF camera, eventually your attention is going to cover about that area. Keep using a 50mm and the attentional field is going to get smaller. That being said, I guess each person could feel more comfortable with a FL that matches how he/she uses their vision in their daily life. Same thing happens with the aspect ratio...

Also, perspective depends only on the distance from the object and not the focal length.

Our brain sensor relies heavily on memory. I wouldn’t say everyone’s memory- both working and long term- is identical. What we see is a brain interpretation and reconstruction of a continuous scanning process, with the current point in time focus of attention the most accurate part of the “image”.

That is indeed the case!

 

[TenEleven]

I am sorry but I am completely lost in you use of "normal" in this post. It seems to be applied in a manner that it has a few different meanings. I know there is a "normal" setting on my washing machine but how you are using it has me lost. And do you mean 7.5 x 11 or 8.5 x 11?

I am of course interpreting what Wes said here, but I guess "normal" in this case means the perspective - so the way the spatial relationships of objects to one another is drawn and not necessarily the field of view, although of course on a technical level these are linked.

Basically, due to the "patchwork" way our eyes (and brain!) sees the spatial relationship and perspective of a 50mm lens feels "normal" (most) of us. This does not include the angle/field of view, which in a 50mm lens, as others have pointed out is somewhat narrower than the (two eyed) view we perceive.

 

[pgk]

The combination eye/brain system does not work like a camera. Ascribing a focal length to the eye, whilst obviously possible because it is a physical system, falls down due to the interpetive operation of the brain which uses memory/experience and numerous interactions in the peripheral vision to create an impression of what is going on around us. Its complcated and gives us a very detailed central view together with an interpolated idea of everything else.

But as individuals we have preferences to do with formats, field of views and ultimately, appropriate preferred focal lengths. Whether these have anything to do with our physical vision is I would suggest, unlikely.

 

[ellisson]

But as individuals we have preferences to do with formats, field of views and ultimately, appropriate preferred focal lengths. Whether these have anything to do with our physical vision is I would suggest, unlikely.

+1

 

[JohnGellings]

I think it comes down to how we perceive a lens when we use it. A very wide angle will push the image back from our point of view vs. our eyes and a telephoto will pull the scene forward vs. our point of view. That is why this normal lens range in the 43mm realm is often quoted. If you stand in one place and bring that lens up to your eye, the scene should not push back or pull forward at all vs your point of view. Of course, we do not put framing rectangles in front of our eyes for everyday use and we of course have two eyes. However, I get why 43mm is usually quoted. It has to do with proximity to subject.