ISO 50 Is A Lie

I just took delivery of an EOS-1Ds Mark III and wanted ask a question about ISO to ensure I’m optimizing the quality of images from this fantastic camera. I’ve been doing studio work with my EOS-1D Mark II and II N on the extended ISO 50. Is there any quality compromise when using this lower ISO? I was using it thinking I would be getting better quality with the lower ISO, but I read something to the effect that it actually increases noise and that extending the range is only a method of light- not quality-management. Am I better off shooting at ISO 100?

The standard ISO range for the EOS-1Ds Mark III camera is 100 to 1600. Optional settings for ISO 50 and ISO 3200 are enabled via menu command, and are indicated on the camera’s LCD data panel as “L” for Low and “H” for High, respectively. Part of the reason behind this is that these settings are not truly ISO 50 or ISO 3200. Instead, in the case of “L,” you’re looking at ISO 100 processed by the camera to achieve an effective rating of ISO 50. Similarly, “H” means that the camera is processing an ISO 1600 image to achieve an effective rating of ISO 3200. “L” images have about the same level of noise as ISO 100 images, but they have less “headroom” in their tone curves to recover overexposed highlights than do ISO 100 images captured with the 1Ds Mark III. This is typically not a problem with evenly lit scenes, but it may become an issue with scenes that have a lot of dynamic range to them, such as sunsets, backlit flash photos, etc.

ISO 50 can be helpful when you are trying to achieve a creative effect, such as a wide aperture to blur the background behind the main subject, for instance in portraiture. It can also be helpful when you are using studio strobes and you don’t want to stop down the lens excessively, or in outdoor situations when you want a longer shutter speed to blur subject movement like the water in a waterfall. But if none of these situations apply, you are better off to use ISO settings in the 100 to 200 range in terms of overall image quality and maximum dynamic range.

© Chuck Westfall

http://digitaljournalist.org/issue0804/tech-tips.html

Words do not express how much this annoys me…

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