Dave Dugdale over at Learning DSLR Video is often reviewing gear from a practical and non-biased viewpoint, and the newest video with DeeJay Scharton from DSLR Film Noob is no exception. With the new Blackmagic Cinema Camera, a 24mm lens is going to become your normal lens, so if you're interested in shooting in lower light at a reasonable focal length, you're most likely going to want a fast 24mm lens. Dave and DeeJay take a look at the Canon 24mm f/1.4 and the Sigma 24mm f/1.8 Macro on both full frame and crop cameras, but the part of the review that will apply most to those who've preordered the BMCC is the performance on the crop sensor camera. Though the crop factor of 1.6 still does not match the 2.3x crop of the BMCC, it's a much better representation of performance than on the full frame camera.
Here is the video review:
This is a little of what Dave had to say about it:
So for build quality it sure seems like the Canon is far superior just because of some of the focus issues we had by just breathing on the Sigma.
So overall I think the Sigma works pretty well for the crop sensor cameras for video, maybe not so much for stills and the Canon works well for both.
There aren't too many fast lenses at this focal length, but it will be an important one because it is the normal lens for the Blackmagic Cinema Camera. We've talked about some other options, like the Samyang 24mm f/1.4, but if you're a stills shooter as well, that lens will not be able to autofocus. There are many factors to consider when buying lenses, and often those on a budget should decide whether they need lenses for video, stills, or both, and buy accordingly. As Dave says, the higher priced Canon seems to do both stills and video just a little better, so that may be something to consider if you also want a good wide lens for taking stills. On the other hand, the Macro ability of the Sigma might make up for its slower speed and sharpness depending on the shooting you do.
If you're not looking at the BMCC, and are shooting video with DSLRs, the sharpness of the lens won't be quite as noticeable since the Canon cameras themselves throw away so much resolution in video mode. This isn't to say you can't notice it, but I've often found that the differences between lenses in video mode isn't nearly as dramatic as it is in stills mode. Certainly, if you're buying a lens to use on a full frame camera like the 5D Mark III, the Canon might be the better option since it was slightly better in the corners on full frame at wider apertures.
In the end it comes down to price, and none of the lenses mentioned will give poor results. I've usually recommend that people buy lenses in Nikon mount since they can be adapted to Canon cameras and will obviously work on Nikon's F-mount, but if you're looking for autofocus, you'll need to get a native Canon mount lens.
Which 24mm lenses do you guys prefer?