The new auto focus development on the 70D closes a rather huge hole in Canon's dSLR ability to handle video focus correctly, as well as the live feed from the sensor. A busy sensor may be an overloaded sensor, but at least, they'll have accurate focus, probably, if their firmware is correct. If they had implemented Contrast Detect Auto Focus, it's likely they wouldn't have had as much of a problem. (Update 2013.12.07: I've been told that the new auto focus works well, so that's in their favour.)
It seems a good breakthrough, but one that will be ignored by professionals, as they'll use manual focus for most anything. Don't you want to control the focus yourself, as they do for films you see in the cinema? Still, Canon wants to hurt any chance for the Panasonic GH3, which is rather firmly entrenched by now, and the Blackmagic Pocket Cinema Camera which should be available any time now. Since both use micro Four-Thirds lenses, Canon might be able to hinder development of third party lenses, although putting pressure on third parties who have to scrape to get their lenses to work with each Canon model might not work so well. Tamron seems to be bowing to pressure.
Live View on the 70D (as well as the D7100) seems to be restrictive, mostly due to the single position rear display. If the world could be gathered in front of a tripod, it might be convenient. However, the world moves at all angles. When using Live View, shouldn't you be able to hold the camera above your head, over a crowd, or hold it near the ground, facing upward? A fully-articulated rear display helps in these matters. If you have to guess at what you're getting, what's the use of Live View?
|Shooting from the ground, comfortably with rear display angled|
Now, I've just seen the Canon EOS-M, their hopeful mirror-less camera, drastically reduced in price because only the fanatics were willing to buy. They have started a small avalanche of sales. After it returns to regular price, will anyone care? I suspect it will sit a lot but the company can still hope. (Update 2013.12.07: They've introduced a follow up model in Japan and it has hybrid auto focus and naturally, a high price, and not much else.)
In general, mirror-less camera equipment isn't selling incredibly well, probably because it's rather expensive. While the Panasonic GH3's price makes sense, how can the GF6 price make sense when the GF6 looks like a point-and-shoot?
It doesn't seem that dSLRs are selling all that well, either, but there are more people who want to look like professionals and could be terribly embarrassed if their friends saw them with something small. Elementary school, anyone? Samsung even did a demonstration in Australia where they hid a mirror-less body inside a dSLR shell. Assumptions are everything.
In any case, I think Panasonic and Blackmagic have no reason to worry about the Canon 70D and Canon users at that level will be happy to switch to a newer body. The GH3 and Pocket Cinema Camera offer too much to film makers to be ignored.
Another tidbit: if you're considering the 70D vs the D7100 for stills, pick the D7100. The weather-sealing and the 51 point auto focus have a lot to offer over the 70D and the only thing that the 70D really offers over the D7100--this new Dual Pixel AF--isn't something worth having unless you have a lot of Canon equipment already. You could do better to buy into a mirror-less camera system. Once again, the GH3 is a very good choice, when video is your main concern but you also need still photography.
Canon 70D Pros:
- Still image quality
- Extensive variety of lenses
- 1.5x zoom factor for lenses--i.e., 70-200mm becomes effective 105-350mm
Panasonic GH3 Pros:
- Video flexibility of formats and bit rates
- Articulating rear display
- Light weight and small size of lenses aids portability in the field
- Remote control from a tablet or smartphone
- Focal length/aperture reducing adapters
Update 2014.12.18: I've got the GH4 now and it contains fixes for most any problem the GH3 had. It's still not perfect, but what is? Auto focus is more certain, especially for video, and I've used it for skate park videos already with success. Is it as clever as the 70D innovation? Probably not. Is it as effective? If I'm not having a problem with focus, I would say so. However, the articulating rear display is a huge bonus on the GH4, as it was on the GH3. As well, being able to operate the GH4 from my tablet or smart phone has made it extra useful.
The Metabones SpeedBooster has become useful to many people, apparently. Being able to take a low light-oriented lens and make it work as an even faster lens is useful. Think of it as a reverse teleconverter. As I've doing more and more video, I'm interested. The SpeedBooster for Nikon G lenses along with the Sigma 18-35mm f/1.8 was suggested to me in particular.
My experience with Four-Thirds/micro Four-Thirds sensors is that you can't expect much past ISO 3200. However, I haven't seen much better from APS-C sized sensors, unfortunately. It takes a much bigger sensor and lower pixel density to fix the sensitivity problems. Still, they're all better than film.