on 2005/02/01 11:46 PM, Moose at olymoose@xxxxxxxxxxxxxxx wrote:
> Resolution Absolute Extinction pixels/LPH
> Horizontal LPH 1400 1650 1.4-1.2
> Vertical LPH 1350 1650 1.4-1.2
>
> The 5200 has 1944 vertical pixels. Now, whatever difference is between
> absolute and extinction resolution, both are much higher than the 972
> your calculation gives. Try the Oly 8080 with 2448 vertical pixels:
Maybe I wasn't clear. I'm saying pixels = LPH for a digital (under ideal
conditions). So your ratio should be 1.00 (under ideal conditions). Under
less than ideal conditions, esp. lower contrast and imperfect alignment, you
may not be resolve as well, so the number will rise above one. Perfect.
What I *am* saying is that to convert to and from traditional lp/mm you need
a factor of two. So a 35mm camera that only resolved 1400 Lines horizontally
would be getting 700 line pairs or about 20 lp/mm. Very low.
Now this is unfair to the digital camera, because the numbers above give the
combined response of lens and sensor, and now that I think of it that's an
even stronger reason for resolution to drop below ideal. In fact, to combine
resolutions in an optical system (approximately) one should use
(1/R1)^2 + (1/R2)^2 = (1/R)^2
If R1 = R2 this results in dividing resolution by sqrt(2), which is about
the ratio you got. Getting a ratio less than sqrt(2) means the lens is
giving significantly better resolution than the sensor - not hard to
believe.
Don't get me wrong - I think digital will eventually outperform film in
almost all respects. And the best is pretty good right now. But my eyes and
the numbers tell me film still has an edge under some circumstances,
contrary to hype and wishful thinking. So I'm still using mainly film.
Andrew
(Who will probably get a midrange digital P&S soon for the ease of
experimentation, replacing his dead low range one.)
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