Thursday, 23 October 2008

A new kind of lens

I've been thinking about this whole field of view thing, and how it relates to lenses. There is the eternal debate about zoom lenses versus primes, the ideal prime focal length, what constitutes a "normal" lens etc. What I figured was it comes down to a difference in "seeing" distance - i.e. the distance to the subject at which one normally focusses.

It's something like this: Traditionally we think of the human field of view as being a cone, effectively equating to a single focal length like this (imagine the dot is a person seen from above & the triangle represents where they can see).

But I did a few experiments of my own and I reckon that actually effective focal length changes with distance. At close distances we see/notice much wider than we do at a distance. The field of view looks something like this (in blue, with the fixed field for comparison).

There could be many reasons for this, or I could be completely wrong but it certainly seems to be the way that I see the world.

So this led me to the idea of an entirely different kind of camera lens. The basic idea is to couple focus point and focal length. At close focus distances the lens would be a wide angle, at grater focus distances the focal length zooms progressively. This means that as you change focus, so to does the field of view. The trick would be to pick a suitable range of focal lengths (which, in principle could be anything). I reckon 24mm (35mm equivalent) for macro distances (a few inches) up to about 90-100mm at infinity would do the trick quite nicely.

I like to think of the idea as a "variable prime" rather than a zoom lens as the focal length is effectively fixed depending on how far away the subject is.

Probably a bonkers idea and maybe impossible to build but would bring a new perspective to photography.

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