From: "James L. Sims" <jlsims@knology.net>
>>>>>>>>>>>>>>
I have been trying to follow this thread, with some difficulty -
probably my old age. But to keep perspective and depth of field equal,
when comparing Full Frame with smaller formats, lens focal length,
circle of confusion, or blur circle, size must be adjusted
proportionately.
<<<<<<<<<<<<<
Exactly. The neat thing is that it all scales. All of it. Very very cool. A
larger format gives you exactly the same functionality as the smaller
format, plus more if you are willing to buy larger lenses or use longer
exposure times. (Assuming identical pixel counts.)
Inversely, if you don't mind the lower sensitivity and lower dynamic range,
you can pack as many pixels as you want into a smaller sensor and still get
high-resolution images.
With film, ISO and film resolution didn't scale, so the lenses seemed faster
and the resolution worse with smaller formats.
>>>>>>>>>>>>
Control of chromatic aberrations become
proportionately more restrictive.
<<<<<<<<<<<<
There must be some things in here that don't scale, I suppose. But for
practical purposes, small cameras work. Very strange.
>>>>>>>>>>>>>>>
Then there's Lord Rayleigh's Criteria
regarding Diffraction Limit is just as true today as it was when he
published it. Therefore, with today's APO lenses, we can achieve very
high quality images, with smaller formats. BUT, to achieve sharp
images, the minimum acceptable lens aperture size will increase (f:#
will decrease) because of diffraction. Having said this, I'm very
pleased with my Canon 20D, The two lenses I have are incredibly sharp,
and zoom lenses at that (I did think that no zoom lens could equal a
prime lens but that may be changing) but I try to stay within its
limitations - shoot at the lowest ISO that I can get away with and
control exposure time to stay within a range of f:4 to f:11.
<<<<<<<<<<<<<<<<<
Yep. The Tamron 28-75/2.8 does amazing work here on the 5D.
David J. Littleboy
davidjl@gol.com
Tokyo, Japan
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