Может, еще и в JPG снимаем?
Шумы я могу огранизовать и на 50 исо среднеформатного задника. Вопрос в руках, все же.
ИСО 400:

Даже на 400 проходные шумы. Показать пример на 100?
Очень не люблю, когда приходят и сообщают что-то вроде "камера отстой, не покупайте". Найдется народ, который послушает и будет это потом пересказывать как истину.
http://www.dpreview.com/reviews/canoneos550d/page29.aspAs you can see from the shooting that we've done for this test, the EOS 550D sets new standards for resolution in its class. In favorable conditions, in raw mode, it is clear that the 550D can unequivocally resolve more detail than an equivalent camera with 12 or 14 million pixels. Resolution in JPEG mode is lower than RAW, as we would expect, but at a pixel level, the difference should not concern most users. Unfortunately, however, the high pixel count of the 550D's CMOS sensor is something of a double-edged sword. Whilst it means that in optimal conditions, with a high quality lens attached, detail resolution is superb, it can also mean that when viewed at 100% on screen, images taken with cheaper, lower quality optics (including the bundled 'kit' option 18-55mm) look distinctly sub-par. It's an obvious point - higher resolution sensors make higher demands on lenses - but it is one which is easily overlooked in the race to put higher and higher pixel counts into low-end and enthusiast DSLRs.
The unavoidable fact is that to get the most out of the 550D's sensor you really need to pair it with Canon's better lenses, which is a considerable investment. Arguably, this is academic for most enthusiast photographers, since most of the time digital images are either admired onscreen or in small (sub-A4) prints. Of course if this is how you primarily view your images (and if we're honest, for most of us it is), it could be argued that packing 18 million pixels is somewhat unnecessary in the first place.
That said, the bottom line here is that the EOS 550D offers excellent image quality in a range of different conditions, including exceptionally low light, thanks to its usable ISO 12800 setting. Image quality is equal or better than its predecessor the EOS 500D, and not noticeably inferior to the considerably more expensive EOS 7D. The 550D's video capability is excellent too.