« on: January 16, 2012, 02:13:32 PM »
Just got enabled to give positive vibes and everyone got +1 in this thread as promised
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Karma is good, it generally keeps the tone civilised I think there is probably a bit of vengeful smiting but i think i applaud more often if i find a post particularly helpfull or brings some good information out
I agree. I've noticed that some participants behave a bit more civilly after receiving some bad Karma. It reduces the number of nasty drive-by comments. No one takes it too seriously, but it's not useless either.
Nope. The diffraction effects correlate with f/number, not with iris diaphagm diameter. That's because the distance between the iris diaphragm and focal plane also matters for diffraction. To expand on your example, 300mm f/11 has an iris diameter twice as large as 150mm f/11, which you are thinking would decrease the effect of diffraction, but at 300mm that iris diaphragm is also twice as far from the focal plane, which increases the effect of diffraction. So, iris diaphragm diameter and focal length effectively cancel each other out, and the f-number ratio is the determining factor.