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DarrynRogers

Camera focal length to match human eye

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I have created a scale model of an installation that I am building. I am using a texture projected from a camera onto a model which is a series of offset planes. The intention is that the image will resolve if a person stands in a particular spot in the room. Everything is working OK except when using a 50mm camera to project the texture the person will need to stand a long way back from the installation for the image to resolve. Much further than I was expecting. Is a 50mm focal length the most accurate approximation of the human eye?

SignMockup.png

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I don't know where you got 50 mm from. Although the focal length of an actual human eye is down around 17mm (calculated via Optometric diopter), the standard the world works to is 22-24mm, which is the value if you calculate it from the physical refraction in the eye.

 

CBR

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Read this article. https://petapixel.com/2012/11/17/the-camera-versus-the-human-eye/

 

@Cerbera is only partially correct. The part of the article that explains why is as follows:

"At this point, both of you who read this far probably have wondered “If the focal length of the eye is 17 or 24mm, why is everyone arguing about whether 35mm or 50mm lenses are the same field of view as the human eye?”

 

The reason is that the the measured focal length of the eye isn’t what determines the angle of view of human vision. I’ll get into this in more detail below, but the main point is that only part of the retina processes the main image we see. (The area of main vision is called the cone of visual attention, the rest of what we see is “peripheral vision”).

 

Studies have measured the cone of visual attention and found it to be about 55 degrees wide. On a 35mm full frame camera, a 43mm lens provides an angle of view of 55 degrees, so that focal length provides exactly the same angle of view that we humans have. Damn if that isn’t halfway between 35mm and 50mm. So the original argument is ended, the actual ‘normal’ lens on a 35mm SLR is neither 35mm nor 50mm, it’s halfway in between."

 

Having read all that, consider that the distance you want people to stand from your installation is critical to the equation. i.e. In the real world, if you used a 50mm lens close to the installation with a camera, you would only see part of the completed graphic and that is why, in the end, a wider angle as @Cerbera mentioned may in fact be what is required.

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47 minutes ago, ABMotion said:

@Cerbera is only partially correct. 

Cerbera was still editing his reply :) But no matter, as long as OP gets the right answer from someone...

 

CBR

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Thanks for the information and links guys. It's super helpful. A wider lens closer to the display is the answer I was hoping for.

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There will come a point at which, depending on how close you want people to stand to get the effect, that it just won't work of course. It will get too wide and look too strange and/or break the illusion. The illusion you are aiming at can only work in specific circumstances. 

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