I rented the 70D last month for the sole purpose of determining whether it would be a worthwhile replacement for my 60D. I also have a 5Dmk3 and 1Dx, but I use those for work and would rather use a lesser camera body for personal stuff. Hence the 60D.
I used the 70D for a four day photo/video project in which I conducted run and gun interviews for documenting a volunteer campaign. Here are a few points worth mentioning:
AF Live view for photos and video:
The AF system works almost as well as a dedicated camcorder. That's no small feat considering the depth of field you're able to obtain with an APS-C sized sensor. The touchscreen is sensitive enough where you can follow focus with it to a great extent. The AF system can be customized to use specific focus points (19 of them) or you can have it set to be center weighted. Face detection also works fairly well, but can be a problem when you have multiple people in frame and you're using an aperture wider than f4 as it will have a tendency to hunt for the correct focal distance. AF live view does have it's limitations though. First, it has problems focusing in high or low contrast situations as it will tend to hunt noticeably longer than usual. Second, the system works best with an STM lens. I compared the 18-135 IS STM vs a 17-55 f2.8 IS. The STM lens' focusing motor is practically silent and focuses notably faster than the 17-55 at the same apertures. The USM focusing motor in the 17-55 makes a lot of clicking noises which will be audible while recording. In this scenario it would be necessary to have an off camera mic unless you want to manually focus using the lens ring.
AF system via Viewfinder:
It's identical to the 7D with 19 cross-type focus points. It's a huge step up from the 60D but a noticeable step down from the 5Dmk3. The viewfinders built-in LCD overlay is pretty neat as you can now enable levels and rule of thirds grids to be seen within the viewfinder. Useful and not a distraction.
Image /Video Quality:
The color profile is pretty much the same as the 60D and 7D. Though I did notice at least 1 stop better ISO noise levels. Essentially, ISO 3200 on the 70D offers similar noise and color detail performance compared to ISO 1600 on the 60D & 7D for both images and video. It doesn't compare to the 5Dmk3 and rightfully so since the FF camera is nearly 3 times the price.
Build Quality:
It feels identical to the 60D and with the exception of a few button placements, they look the same as well. That said, I'm satisfied with it's overall build quality at this price point. Several of my interviews were in a rain forest and I was never concerned with rainfall or humidity harming the camera's internals (I still had the camera wrapped with a weather guard).
Responsiveness:
The camera can shoot at 7fps, but the burst length is not as long as the 7D. The 70D can realistically shoot 8 RAW frames at it's full 7fps, then it will slow down to 1 or 2 shots a second. Whereas the 7D can realistically shoot 15 RAW frames at 8fps before it slows down. Overall, the camera's buttons and menu system worked well, though I prefer the 7D and 5Dmk3's joystick and button layout. In addition, the 70D's playback button is located to the left of the LCD so now you're forced to use both handles on the camera when reviewing your content.
Video Recording:
Similar to the 5Dmk3, the 70D can record in 2 different bit rate levels which is handy because you'll rarely have to record at the highest setting if you're in perfect lighting situations. The higher bit rate will help in post production as the files have more color detail and will result in less noise when adjusting exposure and saturation levels. I wish it could record 1080p at 60fps, but at least you can do it at 720p. The 70D uses the same battery as the 60D, 7D, and 5Dmk3, but I noticed it eats through them at a significantly faster rate than the 60D. You'll probably get a solid hour of video recording with the 70D set at it's highest settings. Have spares ready and consider buying the battery grip (I rented that too and it fits the camera very well...better than the 5Dmk3's grip).
Am I going to buy the 70D to replace my aging 60D? ABSOLUTELY!
The AF live view system was the primary factor and the rest of the feature set is similar to what you'll find on the 7D...just with a slightly improved sensor. All for a lower price? Yeah, it's a bargain in my eyes.
Hope this helps,
David
