ISO noise comparison testRecently at a shoot where the light was low I had cause to use the higher ISO settings in the my Canon 40D camera. Usually I try to stay at ISO 400 where I have always been satisfied with the image quality. I was surprised at the quality of the images at the higher ISOs so I decided to do a comparison test. My Canon 300mm f4L lens was set at f5.6, and the shutter speed varied to allow the same exposure on all images as the ISO was changed in 1\3 EV increments from ISO 200 -1600. Hilight tone priority was enabled which does not allow ISO 100 from being used. The subject was a telephone pole and insulator in sunlight with shadows behind the insulator. The camera was set to RAW and the files were converted to TIF with Breezebrowser Pro. No sharpening or noise reduction was applied with the exception of the two ISO 1600 images that were converted with Noise reduction set for comparison purposes and labeled as such.
Conclusion: As the ISO is increased color noise appears in the darker areas as would be expected. Even at ISO 1600 it does not appear overly objectionable in the lighter shadows and the use of Noise reduction software is effective in removing most of it with a small penalty in resolution. As always exposing properly (just shy of saturation) is the key to low noise.
© Ken Newcombe
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