You can always have low noise by smearing detail. Since you are interested in sharpness/resolution in your comparison, you should look for the best detail, not just the lowest noise.
What might be the best ISO for one purpose (noise in jpgs) might not be the best for other purposes. Yet another will be how easily the raw file responds to PP treatment. And noise is just one of the image parameters that is relevant here. I'm starting to think that you must be joking hard to believe your serious. The only problem might be a slower shutter smearing details, but this is certainly not the case either in the examples I posted or on how I will be shooting. Many parameters improve with lower iso colour, DR and noise. I cannot believe that anyone can seriously think that with good technique at 35mm with SSS on and shutter speed of 1/250s or faster that there is anything other than optimal possible sharpness. The 5D should have the lowest noise and less apparent sharpness, as it is exposed brighter than the other two. I agree with these observations however, the darker exposure of the A-550 will give it a slight advantage in apparent sharpness but at the cost of more noise. Sharpen it up to the A550 detail and see what noise you get from there. Why don't you try the A350 at ISO 200, too? Why stick to the dogmatic "base ISO" when using ISO 200 gives you twice the shutter speed which may have helped in making the A550 shot look sharper?īeyond that, I see the 5D shot as the softest. I second the observation that the A350 shot is a tad softer. They don't even look like bricks on the 350. You can make out the bricks on the 550 shot. Well while the 550 is a bit noisier than the 350, I think it is showing more detail. Well, the sharpness ought not to be an issue at 50mm and 1/60s, and indeed it's not, the brick work on the building in the lower left corner seems to be best shown in the 5d shot.