Right.
And closely related to the info from Wheatfield Willie given earlier, f-stops are
computations of DOF. On many medium format cameras, esp. those with bellows focusing,
you'll see a scale on the side which instructs the user regarding exposure and focus
distance. Look at a photo of the Mamiya RB and C220/C330. These cameras, among
others, have this scale on the side. As a consequence, exposure can change based on
focus distance, though DOF remains the same.
Aperture setting DOES NOT equal identical exposure at differing focus distances.
my 2c
Collin
---ORIGINAL MESSAGE---
<Subject: Re: lens brightness
<A factor affecting light transmission will be lens extension.
<Set to any given aperture, charts typically show that a 50/1.4
<lens will need about 1/3 stop more exposure when focused at 18"
<than it needs at infinity. This may be due to the size of the
<image circle being cast over the negative at varying extensions.
<Mark Rofini
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