[quote name='genotypewriter' timestamp='1297808328' post='6141']
Thanks, Markus... but could you explain how just manual [url="http://en.wikipedia.org/wiki/Bracketing#Focus_bracketing"]focus bracketing[/url] accounts for focus shifts?
[/quote]
Isn't it obvious? If the bracketing is large enough (from slightly in front of the test chart to slightly behind it) you'll have the measurement spots in focus at any aperture in some shots. This not only eliminates focus shifts from the MTF values, but also field curvature.
Of course it takes a little more than 3 shots <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' />
-- Markus
Thanks, Markus... but could you explain how just manual [url="http://en.wikipedia.org/wiki/Bracketing#Focus_bracketing"]focus bracketing[/url] accounts for focus shifts?
[/quote]
Isn't it obvious? If the bracketing is large enough (from slightly in front of the test chart to slightly behind it) you'll have the measurement spots in focus at any aperture in some shots. This not only eliminates focus shifts from the MTF values, but also field curvature.
Of course it takes a little more than 3 shots <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' />-- Markus
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