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Iso 3200

Tony Field

New member
The ability to use ISO 3200 (or ISO 50) is rather strange. Is this an "uncalibrated but sort of legitimate" ISO value or just "extra amplification and the same results can be achieved by using ISO 1600 and playing with photoshop"?

My personal tests indicate that 3200 is better than "push processing" an ISO 1600 image in photoshop (using either raw or jpg). Of course, that could be my inability in photoshop.
 
I thought it was was rather strange myself in that why not just include it, why have to activate it sperately.
The answer I got back from Canon was it imposes extra processing time, so it may slow the top speed of taking pictures. What I still don't know is why it needs extra processing, but since I tend to intensely dislike high ISO anyway and also found that I liked ISO 100 shots slightly better the ISO 50 shots, I just don't use that feature unless I need it specifically for some reason (usually ISO 3200 in low light).
 
AFAICR the extended ISO settings are basically done in software on the camera and are not based on any changes to the A/D conversion on the sensor, while all the normal ISO modes are based on gain control "on chip".

So, ISO 50/3200 can be wholly reproduced by taking shots in ISO 100/1600 (with EV +/-1 to change exposure calculations) respectively and then postprocessing with EV -/+ 1.

This sounds right for 3200, but I would have thought that at ISO50 you would be too prone to overexposing.
 

Stan Jirman

New member
At one point I remember Chuck saying that ISO 50 had less dynamic range than the other "legit" ISOs, and was meant to be used only when you need the slow speed e.g. for running water etc., where you can live with latitude loss.
 

Tom Wilk

New member
Stan, I believe that I saw a dynamic-range test that also showed that ISO 50 lost 2/3 or 1 stop of DR compared to ISO 100. Still very handy when you need to slow things down.
 
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