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Equiv. max. f-stops
#9
[quote name='miro' timestamp='1301098141' post='7098']

Hello Wim,

How do you come to this numbers 1,5 and 1 2/3 stops?

According to my cacluations.



1,5 crop must have 2,25 times higher DOF - in terms of stops it is 1,17 Stops

1,6 crop must have 2,56 times higher DOF - 1,35 Stops.



With Kind Regards,

Miro



PS Finally I fond Wim to say something wrong. :-)

[/quote]

It is a little more complex that that. I don't particularly feel inclined right now to look up the formulas, but it is related to FL, distance and AoV in a reasonably complex way. It is certainly not linear, but also not quadratic. All in all, a direct conversion of linear magnification to f-stop comes very close, however, hence my indication of roughly 1.5 stops for Nikon 1.5 APS-C sensors (slightly more actually) and roughly 1 2/3 stops for Canon (slightly less actually). <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='Big Grin' />



Since this is a very usable rule-of-thumb, this is what I tell people most of the time <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='Big Grin' />.



Warm regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....
  


Messages In This Thread
Equiv. max. f-stops - by Guest - 03-24-2011, 05:54 PM
Equiv. max. f-stops - by Klaus - 03-25-2011, 06:47 PM
Equiv. max. f-stops - by wim - 03-25-2011, 11:08 PM
Equiv. max. f-stops - by miro - 03-26-2011, 12:09 AM
Equiv. max. f-stops - by Guest - 03-26-2011, 10:45 AM
Equiv. max. f-stops - by miro - 03-26-2011, 11:26 AM
Equiv. max. f-stops - by Guest - 03-26-2011, 12:25 PM
Equiv. max. f-stops - by Brightcolours - 03-26-2011, 01:07 PM
Equiv. max. f-stops - by wim - 03-26-2011, 10:27 PM

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