Wednesday, 15 July 2009

Not at the limit yet

Little Man and Skiddaw, Cumbria, May 2009
Shot on 120 roll film, 6x9 on an LF camera

Those who read the Luminous Landscape have probably seen this article by Ray Maxwell ostensibly on the applicability of Moore's Law to camera sensor development, coming to the conclusion that we're hitting the limit, especially in terms of resolution. The arguments didn't look right to me and this TOP article by Ctein neatly debunks the entire thing.

Even with my moderate grasp of the subjects of optics and digital sampling it didn't take long to confirm that the LL article was wrong and to be able to come up with my own calculations (which turned out to be very similar to Ctein's).

Maxwell omitted the Nyquist-Shannon sampling [WARNING: geeky maths link] limits which means we need pixels at most half the size of the given Airy disc or smaller to get full resolution data. Sensor arrays further reduce the pixel size required in order to sample each frequency. I reckoned we can go down to about 1/4 the given Airy disc limit. Of course Maxwell did his numbers at f/11 which suggests large pixels but optics tend to be optimised for larger apertures, with the photographer accepting the resolution/depth of field trade-off for smaller values. Even if we calculate at f/11, with the 1/4 Airy pixel size then that yields a limit of 1.5micron. For comparison a typical pocket camera 1/1.7", 12MP sensor has a pixel pitch of 2micron, so within the grasp of current technology. Compare that to the current 4-6micron for larger sensors and we could happily go to pixel counts 9-16 times those used today before hitting resolution limits.

So your 22MP 35mm full frame could stretch out to around 200-300MP and still yield noticeable resolution improvement. Another upside of extreme resolution is the ability to crop. I could see an argument for using wider angles and cropping for a lot of shots. Imagine only carrying a wide angle and mid-tele for everything. Shoot 100mm and crop the centre for a 400mm equivalent shot. Monster panoramas in one exposure.

Sufficiency is never enough anyway. The sufficiency argument has been touted since cameras hit 4MP.

And all of that ignores any future technology leaps.

[Hereby rewarding a healthy dose of scepticism and justifying my geek tag]


  1. And if you'd got that all wonderful matchbox sized technology in your pocket, I bet you'd still get your 120 film out and carry your bulky LF camera up those Lakeland hills simply because you really enjoyed the process of doing it!

  2. :-)
    At least until my legs or back give out.


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