F-stop theory question

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amacks
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p.1 #1 · F-stop theory question

I think I understand the basic reason why marked F stops start to become meaningless at macro distances, but I have a related question. Does the skew, that is the amount larger the actual f-stop number is from the marked number, increase or decrease with longer focal lenghts?
That is, if I have a 60mm f2.8 and a 100mmf2.8, both focused to make an object appear 1:1, which will be more skewed from the marked f-stop?
a

Nov 03, 2009 at 05:53 PM

LordV
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p.1 #2 · F-stop theory question

AFAIK the Fstop "skew" is mainly linked to magnification not focal length.
Apparent F= F * (1+M) where M is the magnification.

Brian v.

Nov 03, 2009 at 06:05 PM

amacks
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p.1 #3 · F-stop theory question

How is magnification described for that formula? is it the usual macro 1:1 as a fraction or

Nov 03, 2009 at 06:19 PM

Dalantech
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p.1 #4 · F-stop theory question

amacks wrote:
How is magnification described for that formula? is it the usual macro 1:1 as a fraction or

A

Just as a whole number, so 1:1 would be 1, 2:1 would be 2, etc.

Nov 03, 2009 at 07:33 PM


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