This is an experiment to see how using the 3x digital zoom on the Canon EOS 600D/T3i can eliminate moire and aliasing. The idea is simple (I'm not the only one who has had this idea): the 3x digital zoom simply uses a smaller part of the camera's sensor. Thus, it does not need to down-rez (as much or at all). The reduction in the number of lines from the large sensor to relatively lower resolution 1920x1080 is what I understanding to be the source of the aliasing/moire problem. That's not to say that you must have moire as a result, it is just that the processing that these DSLR's do is not as effective at reducing the resolution without these artifacts.
I observed severe moire on the wood bench on my backyard deck. Using the Canon 50mm 1.4 prime lens, the moire in the wood grain is particularly unattractive. Reducing the sharpness helps a little, but not much. The first shot in this video uses a sharpness in the Neutral Picture Style of zero. The next shot increases sharpness to +3, showing a bit more moire.
To defeat the moire, I switched to my Tokina 11-16mm 2.8 zoom lens and engaged the T3i's 3x digital zoom feature. Using the Tokina's 16mm zoom, the combination is equivalent to using a 48mm lens on the T3i without the digital zoom. Similarly, if I used the Tokina at an 11mm zoom plus the T3i's 3x digital zoom, I'd get the equivalent of a 33mm lens. The first clip from the Tokina is not cropped or otherwise scaled. The moire is gone and the frame is slightly larger. The last clip shows both clips (Canon 50mm with no digital zoom vs. Tokina 11-16mm at 16mm optimcal and 3x digital zoom), with the Tokina clip cropped and scaled to fit the same frame as the 50mm.
To me, the results are great. The moire is eliminated. I know this won't work in every situation, but it is a handy trick to have available.
There are unsurprising costs. The depth of field is deeper. The image appears just a little soft with the digital zoom, albeit with decent detail -- and I might not have the focus perfect. For me, I'll trade off the moire in favor of a little softness in the image if I have no choice. The other cost isn't shown in this video, but I've seen it in other video I've shot with the 3x zoom. The noise at higher ISO's is (not surprisingly) worse in the 3x zoom mode. So, the tradeoff might not be so clear in a low-light setting, as the ISO noise might be more offensive than the moire. My guess is that this might become an issue at ISO 800+ or so. But, in daylight, is unlikely to be an issue.
This video isn't intended to knock the Canon DSLR's at all. In fact, I love my T3i and T2i. One of the best-known drawbacks of these camera's for video is the moire. To me, this little workaround can really help out in a bind if you have a wide-angle lens, such as the Tokina 11-16mm, and you don't need anything wider than a 35mm on the shot that has the moire issues. Most people think the T3i's digital zoom is just good for telephoto purposes. For me, the elimination of moire makes it a great feature to have. Since I already have the Tokina (and love it), I'll use it with the 3x zoom when I have to in order to eliminate moire. I will not use it to replace a 50mm otherwise, as I prefer having the sharpness and shallow depth of field option if I don't have to worry about moire.
I used ISO 160 (using Magic Lantern) and f14. I didn't move the camera between lenses. I tried to match the color and contrast of the images with very small adjustments in Magic Bullet Looks and Sony Vegas Pro. I did not adjust sharpness of the clips (I think the Tokina image could have benefitted from a bit of sharpness added in post). I also tried this with ISO 100 and the results were identical.
I hope you find this helpful and I welcome your comments, criticisms and suggestions.