I have to admit that when it comes to ISO, I've always assumed that the base ISO was going to have the cleanest output. I had read articles on how some models of cameras were noisier at the 'in-between' ISOs (ISO 125 and 160) than the base numbers (100, 200, 400). This was true on a camera I had a while back, so I didn't really give it another thought.
I read an article in a magazine (link here) where someone took a Canon 7D with a lens cap on and compared the noise with the levels boosted up. It isn't as dramatic as the article made out, but the results surprised me a little. Turns out my 7D is just as good (or better) at ISO 160 than it is at ISO 100. That is a 2/3 of a stop bonus with no penalty! Try getting that much more aperture on all your lenses for free :)
I'm not going to argue that this will change your life or anything, but after doing some testing I will be sticking to ISO 160, 320 and 640 over the 'whole' numbers. The point in the article is there is more going on than just the base ISO - that all the electronics and processing come into the picture. It is worth a few minutes taking a few shots and convince yourself that the ISO values you think are cleanest, really are. I was surprised to find banding in the shadows at ISO 400, but not ISO 640. I should hasten to add that I'm talking about boosting overexposure by +4 stops to make it obvious - but the point is that if in a carefully controlled experiment I can't tell the difference between ISO 100 and 160 or 400 and 640, why would I hesitate to use the higher value?
Thanks for sharing. This is indeed a very interesting finding. I have tried on my 550D from ISO 100 to 12800 in 1 stop increment but didn't found that any of the higher ISO setting is better than the lower ones.
If this is the characteristic of all 7D, we can shoot indoor at ISO 640 without any hesitation. :-)
I have been doing a little experimenting recently after reading some bits and pieces about ISO performance and am getting much better results at ISO200 for isolated studio shots against a white background than I was getting at ISO100.
I use a Canon 450D and I put it down to the image being better exposed with the extra stop so when I do the raw conversion I am not doing as much to the image and what noiuse I am introducing is being dealt with by noise ninja with no issue or significant degredation.
I think one should not automatically believe the lowest ISO is the best for noise. But even if it is, there are other considerations. It is better if you can use faster shutter speed in most cases, even if you work from a tripod. I noticed in case of my camera the ISO 200 is just as good noise wise as ISO 100. So I never go there. I can see slight noise impact at 400 so I am using it selectively. I never tried the intermediate ISOs.
I should note that the test they did is by no means a scientific one. It could be that ISO 160 is the cleanest because it does the most noise reduction and it would be at the expense of detail, or dynamic range, etc. Bottom line is, though, play around with it and see what ISO settings you are happy with...and naturally different cameras will have different results.
In some journals or websites you can find special ( laboratory ) tests of "our" products, including noise. As far as I remember, really you can see there that, for example, ISO 800 is in some cases better then lower one. If we are talking about D90 ( I also have it and am very satisfied), the lowest ISO as a default is 200. If you go to menu and choose lower one, there should be, beside noise, also a slightly lower contrast.
that´s a great topic.. my D90 actually starts at 200 but I never shoot at 200, I set always to 100 lol.. is there a big diffence, is it worst? don´t know.. guess I will have to try it out, I guess it comes on default on 200 to help exposure time but actually who buy a D90 know to raise the iso value right?
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