Saying that, I'm impressed about the review that Dpreview gave for the Canon Rebel T3i / EOS 600D. Yes, you are right...sales and marketing are an important part of this business, but they still seem to produce quality products to match their advertising. I don't know everything about Canon cameras and lenses, but just enough to say that I'm impressed. Canon must be doing something right, if they are expanding like that. What brought you to say, when you wrote "high-end cameras are inferior in some ways to low-end ones"? Do you have specific examples?
Canon's DSLRs have artifacts such that any exposure that isn't strong for the ISO, especially low ISOs, have stripes or burlap patterns in them, both thin and thick. The thick ones survive downsizing or small image display sizes very well. There are three factors which, besides one's own "under-exposure" cause the camera to under-expose under the hood, increasing the risk of you encountering these artifacts. One is "Highlight Tone Priority", which under-exposes an image by a stop. Then, the 125/250/500 series of ISOs under-expose another 1/3 stop. Then, fast lenses wide open cause up to another 2/3 stop or more - combined, these things can very easily bring out the ugly artifacts in the shadows. Take a camera like the Nikon D5100, which costs about US$775, as cheap as a rebel, and has a noise floor 2.5 stops lower than a Rebel. Rebels aren't the worst Canons for low-ISO shadow artifacts, though; the 5Dmk2, 7D, and 1Dmk4 are the worst at that, of recent Canons. With my US$2700 5Dmk2, if I expose at ISO 100 so that a white building in the sun just barely avoids blowing out, the shady side of the street is unusable, with big colored lines running through that part of the image. With a D5100, at about 30% the price, these shadows would be totally usable.
Canon's auto-ISO is horrendous. My 5Dmk2 doesn't even have it in manual mode; in none of my Canon DSLRs does flash work in auto-ISO; as soon as you turn the flash on, the camera fixes at ISO 400, and I get black images with specular highlights from the flash. You can't tell the camera a minimum shutter speed to use, or limit the aperture in any way, when those parameters are floating (automatic).
Now understand why I feel enraged that the public is not aware of these things, and avoiding Canon products. As long as Canon continues to sell on the momentum of name recognition, the longer it will take before they feel compelled to provide clean shadows at low ISOs, and basic, properly functioning auto-ISO.
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John