Grrr Not sure why the site thought I "forgot my password" when I quite emphatically DIDN'T forget it, but now that I've gotten my rant that is tangent to the topic out of the way....
I've owned a 7D for about a year and a half now. I find the 70D vs 7D to be an interesting comparison. When it was announced that the 70D would have "the same" 19 point AF system as the 7D, I wondered that was really the case or if its Servo accuracy would be improved. The LensRentals results showing that the new AF systems in the 1DX and 5D Mark III had massive improvements in Servo tracking, even against such heavy hitters as the 1D Mark IV, so I thought it might be likely that the 70D's system would be more accurate. Based on various reviews, and posts CR, I'm satisfied that it has been substantially improved, despite being labelled "the same." I'm definitely +1 in the camp that AF is crucial to IQ. A clean out of focus image, is still and OOF image!
In addition, I've seen some of the IQ issues with the 7D that have been reported. My 7D blows my T3i out of the water for most things. It's AF may not be equal to the 70D's and not nearly as good as the 5D Mark III or the especially AF speed and accuracy on moving subjects, but it is still a great system that beats the Rebel hands down, as one would expect. But I've seen some of the sky noise at 100 ISO in airshow pics--the T3i (used as a second body), does seem to create cleaner images that require less editing. Still, I find my 7D images clean up nicely in post (I'm just using DPP).
Based on the reviews I've read, it seems that the 70D has made some progress on both the IQ and AF fronts, making it a compelling camera. Two AF features it's missing though are AF Expansion and AF Spot mode. I have read many reviews that make light of these two modes, but I've found them very useful. AF Expansion is very useful for tracking a fast moving BIF. And I find Spot mode far more useful than I'd originally thought, when trying to get a lock on a bird through dense foliage. I've gotten some shots with Spot mode that would probably have been impossible without it. The year prior to buying my 7D, I was trying to get images of Bald Eagles nesting in Port Colborne (a town near me in the Niagara Peninsula of Ontario, Canada) with my T3i, and I was constantly frustrated by the AF system focussing on a branch in front of the subject. The Spot AF system would have been a huge benefit! I've since used the Spot AF in tricky situations with birds and other animals, which naturally try to seek cover when confronted with a curious human armed with a large tube they keep trying to aim at them, for unknown purposes! :
I'm a little surprised that Spot and Expansion modes are disabled in the 70D. Likely just a firmware feature, perhaps left off to give a bit of 'separation' between the xxD series 70D and the xD series 7D, which nominally sits above it. Perhaps, once the 7D is discontinued, the 70D will gain these features in a FW update!
As compelling as the 70D is, it doesn't really bring enough to the table for me to change to it, especially since I only purchased my 7D in 2012. It's the 7D Mark II that interests me, as I want a quantum leap in AF capability, and also hope for substantial burst and buffer improvements (as well as some IQ improvements, but I'm expecting those to be more modest than the AF and burst changes). If I was buying new however, I think it would be a tougher proposition. IQ and AF accuracy favour the 70D, which is to be expected. For the Videographer of course, it's a no-brainer--the 70D beats the 7D hands down for video. The tilt-shift screen may erode weather sealing, but it can also be very useful in some shooting scenarios, where one wants or needs to shoot at odd angles, and the DPAF on the 70D can be very useful for that, although I find shooting in Quick AF mode during live view largely makes AF speed in live view a non-issue. On the other hand, the 7D does have the (slightly) faster burst mode and, more importantly, a deeper buffer. It also has the two additional AF modes which, although often overlooked, can be extremely useful for the "action" shooter. I'd be in a tough, tough place if I was buying new for the first time!!!! The 70D I think wins overall, incorporating new technology, but I'd really miss the deeper buffer and extra AF modes!
Regarding the D7100 vs 70D, vs 7D comparison, I think it largely depends on what you're shooting and in what conditions. Many have stated that the D7100 is probably the better "stills" camera, but I believe that is a statement that needs clarification and qualification. I think if I was shooting under low light, the D7100 sensor does have some advantages, which has been covered extensively. I very much agree with the earlier post however, that people often overstate the DR issue, ignoring the Canon system's other strengths. It certainly does seem to be a case of people fixating on the "C" and ignoring the A's"! Given that it is designed, like the 70D, for action shooting, I'd say the D7100's biggest downfall is the shallow buffer, even for JPEG shooting. This seems to be the biggest Achilles heel for an otherwise outstanding camera. Another interesting comparison between the 70D and the D7100 also revolves around AF systems. Many reviewers seem to fixate on the fact that the D7100 has 51 AF points vs only 19 on the 70D, and thus automatically give the D7100 the nod. However, it’s less simple that that—only 15 of the D7100s AF points are cross-type, whilst all 19 of the 70D’s are cross-type. Moreover, what really matters is how well they work in real life.
There is an interesting review at
https://www.youtube.com/watch?v=bOM4r1gxsbs. There doesn’t seem to be much to choose from in terms of AF accuracy for side-moving subjects, but the tests definitely give the edge to the 70D when it comes to advancing or receding subjects. I think it’s interesting how Canon and Nikon appear to fluctuate when it comes to various parameters of camera design, but it does seem , from a number of comparisons I’ve read or viewed, that Canon has gained a slight edge in AF speed and accuracy over the last few years, beginning with the 1DX. The review also covers the difference in buffers. Unfortunately, the reviewer only covers JPEG and RAW+JPEG buffers. I’d have liked to have seen a RAW only comparison as well, as the 70D is reputed to be good for 15 or 16 RAW shots before the buffer fills, which is certainly not bad!
In the end, I would say I’m happy with my 7D overall. Yes, I’d love to get something that has an even better AF system and better IQ. The 70D appears to deliver, but not sufficiently for me to consider it. The much anticipated 7D Mark II is the beast for which I am yearning! It’s possible that a 70D might end up in my bag, way down the road when the price is lower—it might make a better second body to go with the 7D Mark II than my 7D will, and give me a much better “tilt screen” camera than my T3i ( I will always want to have at least one SLR with a tilt screen!). If I was going to advise someone on deciding between the 7D vs 70D, I’d probably recommend the 70D given that it has better sharpness, noise –control and newer technology, such as DPAF. Unless of course they needed maximum durability and a much deeper buffer, in which case I’d say the 7D is still very difficult to beat. The 7D may be an “old” horse it the unforgiving technology race---but it’s STILL a damn FINE horse!!!!
