Canon DSLRs are popular for video shooting, and you can pull beautiful footage from the low end Rebel series to the high end 1D series. But what is the difference in image quality in a price range from $1000-$7000? We've had a Rebel T4i, 5D Mark III, and 1DX all in ou possession, so we decided to take a closer look.
We took all three cameras and shot the same scene with the same lens (Canon 24-105 f/4) and settings (f/9, 1/50, ISO 100). We use a picture style with sharpness at 0, contrast at 0, and saturation at -2. We adjusted the focal length on the crop-sensor t4i to match that of the other two cameras. Obviously this isn't completely scientific, but we did our best.
When viewed on the web at less than full-screen, the differences between the three are very faint. But when you blow 'er up a bit, the first thing that stands out is the terrible moire patterns in the T4i shot. Look at the false color in the bricks. Clearly the 5DMK3 and the 1DX are worlds better at resolving that type of detail.
As for image sharpness, there difference is ever so slight, but the 1DX is a bit better than the 5DMK3, and the 5DMK3 is a bit better than the T4i. You can see it best in the leaves of the trees.
For the last step we added a bit of sharpness in post (Sharpen effect in Premiere Pro CS6, value of 55) to see how the footage responded. The difference immediately became clearer at 350% crop. The 5DMK3 lost a lot of detail and displayed more noise than the 1DX, while the T4i became sludgy and gross. Ew.
But AGAIN, this is pixel-peeping! Yes, the T4i's low price is reflected in that terrible moire, but the difference in video quality on those higher end cameras is minuscule. Paying $6700 for a 1DX will get you a tad bit more sharpness, and probably a bit better performance at high ISOs (though we have not tested this yet). The 1DX's real benefits are almost entirely in its beastly photo-snapping capabilities.