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 Author
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Topic: Auto ISO and exposure compensation (Read 8059 times)
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Frank Kolwicz
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I recently looked at an article about the usefulness of Auto ISO for wildlife photography and gave it a try with my 70d and 5dII.
The recommendation was to set the camera on Manual with Shutter Speed and Aperture preset for whatever conditions (subject movement, focal length) you are using and let the ISO setting "float" to whatever is necessary to get proper exposure. The only benefit I can see is to allow the possible use of the lower ISO settings to reduce noise, when conditions permit. BUT, with my cameras that means giving up using ETTR, "expose to the right", to achieve the same goal - lower noise - since the cameras don't allow exposure compensation when in Manual Mode (as near as I can tell) and I always use ETTR at ISO 1600 and do a noise reduction when editing for a print.
Rather than reinvent that wheel and go through another round of extensive testing, like I had to do a dozen times this year for focus problems, has anyone made the comparison between the two alternatives? Have a link to an article?
Thanks,
Frank
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Bob Atkins
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The new firmware for the EOS 1D X gives you the ability to use exposure compensation in manual mode, but I guess that doesn't help you! Not sure if the new 5d MkIII firmware permits this or not. However it's not likely to be introduced for the 5D MkII and I doubt the EOS 70D will see it either. Maybe the 7D MkII?
It's going to depend on circumstances. Shooting a great blue heron with spot metering should be fine in auto ISO. Shooting snowy owl might benefit from manual choice of ISO (or EC if you had it)
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KeithB
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If you are in manual mode, *you* are the exposure compensation. Note that exposure compensation didn't exist until there were automatic exposure modes.
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Frank Kolwicz
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Keith,
Are you aware that in Auto-ISO Manual mode the camera prevents you from making exposure compensation by changing the ISO when you change either aperture or shutter speed?
Frank
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Bob Atkins
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Frank is correct. If you are in manual mode and set fixed ISO, then, as Keith says, you are the exposure compensation. However in manual mode with auto ISO you are effectively in an auto exposure mode and on most EOS bodies, you can't use exposure compensation.
That feature was added to the EOS 1D X in the latest firmware because of feedback from pro users who wanted it.
Why it's not available on all EOS bodies is a mystery. It would be trival to add. I guess Canon software engineers never though users would want it (and indeed, most users probably don't need it or don't even realize they don't have it!).
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KeithB
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It could be too, that Canon still does not consider ISO changing to be an "exposure change". Eg, since the film-based EOS couldn't willy-nilly change ISO when in manual mode, the digital bodies don't either.
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Bob Atkins
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That could well be. It's a case of "that's the way we've always done it" and the firmware designers still thinking of the days of film cameras.
Most Nikon DSLRs do have EC in manual mode with auto ISO, even some entry level models. Perhaps Canon will start including it in future cameras now that they've "seen the light" with the new firmware for the EOS 1D X
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