Read about the Camera ISO noise tests in the help section to learn more about the tests and how they are conducted. A key take-away from that page is that noise reduction is completely off unless otherwise specified.
There are many MB of files required to be downloaded to make all of the mouseclicks on this page function properly - please be patient while they load.
Looking at the 10.1 megapixel Rebel XS/1000D image crop overlaid on the same image crop from the Rebel T1i/550D shows how far 18 megapixels takes us in the same size sensor. All things being equal, the outline of the Rebel XS image simulates how much of a full T2i image can be cropped while retaining 10.1 megapixels of image. This difference equates to the additional "reach" of the T2i's sensor (bird and distant wildlife photographers know what I'm talking about). The same comparisons apply to the 7D as it has the same sensor density.
What I'm primarily trying to show in this comparison is how much noise is present in images at various ISO levels with no noise reduction applied. The solid color blocks make the noise very obvious.
The Rebel XS/1000D produces a sharper image but has noticeably more high ISO noise than the T2i. The XSi/450D comes closer to the T2i in both resolution and high ISO noise, but the T2i is still the winner in this comparison - showing less grainy-appearing noise at high ISO values. Obvious is that the T2i provides 3 additional stops of high ISO settings compared to these bodies - an advantage it does not hold in the rest of the provided comparisons.
I intentionally positioned the Rebel T2i/550D results between the T1i/500D (the previous Rebel model) and the 7D (the other 18 megapixel DSLR). While the brighter image delivered by the T1i/500D makes a comparison slightly more difficult, I'm still seeing reduced noise in the T2i - by an amount that exceeds my expectations. And the T1i has slightly less noise than the 50D.
The EOS 7D delivers the most-comparable image in both resolution and in noise performance. I don't see a significant difference between the images from these two cameras, but give the T2i the slight edge. In my opinion, high ISO noise performance is not a differentiator between these two cameras.
With its high resolution full-frame sensor, the 5D Mark II leads this contest with impressive image quality.
I usually use the lowest ISO setting that will give me the exposure parameters I want for a shot. And I consider the T2i's ISO 12800 an extreme last resort for capturing an image. Images are barely useable for even a small output size at this ISO setting. Sure, having the option is better than not having the option, but I will not be using ISO 12800 very often.
The with-noise-reduction examples have a range of noise reduction added - from 1,2 (Luminance, Chrominance) at ISO 100 up to 8,16 at ISO 12800. These examples show that noise reduction (which could be applied at various stages in the image processing pipeline) clearly reduces the visible noise - and reduces the fine details as well. Since low noise and high detail resolution are both strongly desired, the next set of comparisons looks at how much detail is retained at higher ISO levels.
The big image quality difference between the examples in this comparison is directly related to the resolution of the camera's sensor. The T2i resolves significantly more detail than the 10.1 megapixel Rebel XS. The rest of the Rebel models fall in line between these two.
Back to the Canon EOS Rebel T2i / 550D Review.
Bringing you this site is my full time job (typically 60-80 hours per week). Thus, I depend solely on the commissions received from you using the links on this site to make any purchase. I am grateful for your support! - Bryan