05-18-2011, 11:12 PM
[quote name='mst' timestamp='1305759017' post='8561']
It's actually more like 1 stop. So, a 85/2 would actually be the "real" equivalent to a 135/2.8 FX lens. Or one could argue that a 85/1.8 behaves more like a 135/2.5.
However, the difference between f/2.8 and f/2.5 (or f/1.8 and f/2 for that matter) is marginal in the real world. So, 1 stop difference as rule of thumb works quite well.
-- Markus
[/quote]
Not really, the difference is a bit more than 1... more like 1 1/3rd stop.
f1.8 and f2.8 actually really are the equivalents (more or less).
It's actually more like 1 stop. So, a 85/2 would actually be the "real" equivalent to a 135/2.8 FX lens. Or one could argue that a 85/1.8 behaves more like a 135/2.5.
However, the difference between f/2.8 and f/2.5 (or f/1.8 and f/2 for that matter) is marginal in the real world. So, 1 stop difference as rule of thumb works quite well.
-- Markus
[/quote]
Not really, the difference is a bit more than 1... more like 1 1/3rd stop.
f1.8 and f2.8 actually really are the equivalents (more or less).