Following are the pair of 100% crop image quality comparisons I have been including in my Canon EOS DSLR Reviews. Read about the Camera ISO noise tests in the help section to learn more about these tests and how they are performed. 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 links on this page function properly - please be patient while they load. Click on the ISO setting for the camera you wish to see results for. Then click on another link to compare results for another camera and/or setting.
These cameras all perform excellently. Canon has made no claims for improved ISO noise performance from the 70D's new sensor (they would have if they thought it was improved in this regard), but it definitely appears that the higher resolution Dual Pixel CMOS design (more about this later) gives up no ground to the other APS-C imaging sensors.
While we would all like to think otherwise, the big improvements in APS-C high ISO noise we used to see have not happened in recent years. I think the 70D is as good as any other model on the above list and even better than some (at least at some higher ISO settings).
I do need to point out the sharpness issue. While the settings for these tests are standardized, the 7D and 60D images are slightly soft while the T4i images are slightly sharp. Increased sharpness generally makes noise more obvious. You can always adjust your image settings to your own taste.
The 70D images, processed at my standardized settings, fall between the just-mentioned cameras in terms of sharpness. And as I said before, I find the 70D's amount of sharpness to be just right. That the 70D images are sharper but not noisier than the 7D's images indicates to me that some improvement in noise is being made here.
If the difference in image quality is hard for you to detect, I don't think you have a justification for an upgrade (there are plenty of other upgrade reasons). If you need less noise in your high ISO images, the full frame sensor cameras including the 6D, 5D III and 1D X are your answer.
One of the 70D's upgraded-from-the-7D/60D capabilities that is not going to justify an upgrade for most is ISO 25600. This setting has far more benefit for marketing than for real use. ISO 12800 images also look bad and ISO 6400 images are still not exciting.
As always, in-camera noise reduction is available. And, as always, noise reduction is available during post processing. The last two rows of results show the 70D's in-camera noise reduction in use.
These two NR sample sets were captured in JPG-format using the same settings used for RAW processing of the other images: the Standard Picture Style with sharpness set to "1" (very low) (settings applied in-camera).
The first noise reduction sample set used the standard noise reduction level (high and low settings are also available). Standard is the default out-of-the-box setting for the camera. And the results above show the reason I immediately turn off noise reduction for my default. See the oversharpening halos around the color blocks and the slightly reduced image sharpness at ISO 100? Noise reduction also degrades fine details in an image. I generally do not add noise reduction until reaching very high ISO settings, but this is of course your choice.
Multi-Shot Noise Reduction is relatively new for EOS DSLR cameras. When this feature first appeared, I was anxious to see how the merging of multiple (four) exposures taken in a full-frame-rate burst could be used to reduce image noise as the concept makes a lot of sense. The bottom set of NR examples shows the test results from MSNR and the NR set directly above it provides a direct comparison with the standard NR. There is definitely improvement with MS NR - a full stop or more at some ISO settings - including even low settings.
Downsides to Multi-Shot Noise Reduction include: MSNR is currently available only with JPG output (I would like to see this feature added to Canon's Digital Photo Pro software for RAW capture processing - perhaps as another HDR preset). Multi-Shot Noise Reduction will not be so useful with moving subjects. Long exposure NR, Dust Delete Data, Multiple Exposure and HDR Mode must be set to off to enable MSNR. The 70D reverts back to Standard NR in Basic zone modes, during video recording, in Bulb mode and when the camera is powered off. Flash is not supported in MSNR mode. And the camera remains "busy" for a brief period of time after the 4 shot burst - while processing the merged image. This feature is nice, but I have not found it so useful in real applications.
Here is another noise comparison that includes fine details in a piece of fabric.
The fine details in the fabric better-hide high ISO noise and favor higher resolution sensors. In this comparison, the 70D easily bests all of the other APS-C sensor format DSLRs – especially the 7D. Again, the full frame 6D and 5D III flex their muscle in this comparison.
As I mentioned above, noise reduction reduces image detail. This fact becomes apparent when comparing the 70D's ISO 100 results with and without noise reduction. Standard noise reduction at ISO 12800 removes nearly all detail.
Overall, I think the 70D looks excellent from an image quality perspective.
Back to the Canon EOS 70D Review.