This is going to be short, since I've not had the chance to do a whole lot of shooting as yet. Consider it a "just out of the box" impression. I already have a Canon 5D Mk III, and a number of L series lenses. I wanted a "backup camera" for video shooting, and I was intrigued by the new auto-focus system offered on the 70D.
So far, I'm extremely pleased with this camera. The 18-35 mm kit lens gives a lot of range, and I tested the camera out with my other lenses. The L series lenses work very well, and auto-focusing is fast, smooth, and doesn't search around much even in very low light. The camera is not as heavy as the 5D Mk III, but feels solid enough, and not all that different in the hands. Even with the 70-300mm f4-5.6L IS USM zoom - my heaviest lens at the moment - the camera feels surprisingly balanced.
The crop sensor obviously changes the effect of the lenses, but having a full sensor and a crop sensor both, it's like having 2 sets of lenses. My 70-300mm zoom now has an effective reach up to 480 mm (on the Canon 70D) due to the crop factor of 1.6. To me, this is kind of a bonus, though not in itself a reason to buy the camera. Smaller sized sensors result in an apparent increase in focal length, and a greater depth of field, but this is a generalization and each lens has its own properties that affect the image as well. Read the reviews of individual lenses when considering how each one reacts to different types of camera bodies.
The main thing to take note of is that while the Canon 70D will accept all the EF and EF-L lenses, it is designed to use the EF-S series lenses as well. In fact, the EF-S series lenses are custom tailored specifically for the Canon 70D and (as far as I know) other APS-C crop sensor cameras made by Canon. These lenses - and the kit lens is one of them - will not work on a full frame camera like the Canon 5D mkIII; the rear element extends back into the camera body in a way that makes it impossible to attach lenses of this series to full frame sensor cameras. Even if they could be attached, I suspect the captured image might suffer from serious vignetting and other problems.
For a thorough understanding of how the APS-C, full frame and other types of sensors interact with various lenses, I highly recommend doing some research on the web. There's a lot of good information out there, and this is a fairly involved subject that I don't even want to attempt to dive into here :)
One thing I couldn't figure out before having the camera in my possession deserves a mention. This is my first experience with a fold-out LCD screen on a DSLR, and I had no idea how the display would deal with flipping around 180 degrees. Would it be upside down? This was the first thing I tried, and the screen auto-flips when it is rotated. Maybe everyone else already knows this - but I didn't! Anyway, the fold-out display is a great feature, and it also folds face-in to protect the display when not in use.
The ability to touch various points on the LCD display while in Live View or shooting video, and shift focus while shooting is - to me at least - worth the price of admission. If Canon eventually updates the 7D and/or the 5D Mk III, this functionality would be most welcome!
Purely as a "gut reaction" - I really like the 70D immensely. And it seems a very good value for the price. This may actually become my preferred "walk-around camera, though time will tell.
EDIT - 10/22/2013: I've spent a lot more time with the camera now, so I can add to my earlier comments.
While I purchased the 70D mainly for shooting video, I recently used it to shoot bracketed exposures for HDR (high dynamic range) panoramas. A friend of mine had a nodal camera head (The "Ninja" head) which allowed for precise rotation of the camera to cover a full 360 degree field-of-view. The Canon 70D allows for up to 7 bracketed exposures via the AEB controls. The plates were shot in the RAW (CR2) format, using the kit lens, and stitched together using PTGui software.
After some initial trial runs, where we ironed out the kinks in the whole process, the results were exceptional. For those who may be wondering "why do you want a 32 bit HDR 360 panorama at 10k-16k resolution?" it is used to create realistic lighting and reflections in a 3D/CG software (i.e. Modo or Maya, for example). The 3D scene can be lit entirely by the 360 panoramic image, producing a very convincing result.
At any rate, the Canon 70D delivered terrific results doing something I didn't even foresee when I bought the camera. I will try and upload some of the tests (where the photographic panorama serves as both background and light-source) if I can figure out how to do so on the Amazon site.
EDIT - 11/9/2013: A note to anyone who intends to shoot green screen (for color keyed composites) or do precise color grading in post production: The video output from the 70D is not YCbCr 4:2:2 compression. This is not apparent to the naked eye when viewing the video footage, but it becomes an issue when attempting to work with the footage in a post environment. The firmware update for the Canon 5D addressed this problem by enabling 4:2:2 color output via the HDMI port to an external recording device (I use the Atomos Ninja 2 for this) but currently uncompressed "clean" HDMI is not enabled on the Canon 70D. I have my fingers crossed this will be dealt with in an update to the firmware.
This is not a huge issue unless you intend to do extensive manipulation of your video footage in post production, but it is something to consider with this camera and DSLRs in general. There are workarounds, of course, but that can entail a fair amount of time & effort, particularly when extracting color key mattes (masks) involving fine edge detail or areas of transparency.
That being said, the footage is nevertheless beautiful. And I suspect this technical point should not be an issue for most people considering buying the Canon 70D. The CR2 (camera raw) files are not at all affected by this, it's a factor limited to the HD video.
So far, I'm extremely pleased with this camera. The 18-35 mm kit lens gives a lot of range, and I tested the camera out with my other lenses. The L series lenses work very well, and auto-focusing is fast, smooth, and doesn't search around much even in very low light. The camera is not as heavy as the 5D Mk III, but feels solid enough, and not all that different in the hands. Even with the 70-300mm f4-5.6L IS USM zoom - my heaviest lens at the moment - the camera feels surprisingly balanced.
The crop sensor obviously changes the effect of the lenses, but having a full sensor and a crop sensor both, it's like having 2 sets of lenses. My 70-300mm zoom now has an effective reach up to 480 mm (on the Canon 70D) due to the crop factor of 1.6. To me, this is kind of a bonus, though not in itself a reason to buy the camera. Smaller sized sensors result in an apparent increase in focal length, and a greater depth of field, but this is a generalization and each lens has its own properties that affect the image as well. Read the reviews of individual lenses when considering how each one reacts to different types of camera bodies.
The main thing to take note of is that while the Canon 70D will accept all the EF and EF-L lenses, it is designed to use the EF-S series lenses as well. In fact, the EF-S series lenses are custom tailored specifically for the Canon 70D and (as far as I know) other APS-C crop sensor cameras made by Canon. These lenses - and the kit lens is one of them - will not work on a full frame camera like the Canon 5D mkIII; the rear element extends back into the camera body in a way that makes it impossible to attach lenses of this series to full frame sensor cameras. Even if they could be attached, I suspect the captured image might suffer from serious vignetting and other problems.
For a thorough understanding of how the APS-C, full frame and other types of sensors interact with various lenses, I highly recommend doing some research on the web. There's a lot of good information out there, and this is a fairly involved subject that I don't even want to attempt to dive into here :)
One thing I couldn't figure out before having the camera in my possession deserves a mention. This is my first experience with a fold-out LCD screen on a DSLR, and I had no idea how the display would deal with flipping around 180 degrees. Would it be upside down? This was the first thing I tried, and the screen auto-flips when it is rotated. Maybe everyone else already knows this - but I didn't! Anyway, the fold-out display is a great feature, and it also folds face-in to protect the display when not in use.
The ability to touch various points on the LCD display while in Live View or shooting video, and shift focus while shooting is - to me at least - worth the price of admission. If Canon eventually updates the 7D and/or the 5D Mk III, this functionality would be most welcome!
Purely as a "gut reaction" - I really like the 70D immensely. And it seems a very good value for the price. This may actually become my preferred "walk-around camera, though time will tell.
EDIT - 10/22/2013: I've spent a lot more time with the camera now, so I can add to my earlier comments.
While I purchased the 70D mainly for shooting video, I recently used it to shoot bracketed exposures for HDR (high dynamic range) panoramas. A friend of mine had a nodal camera head (The "Ninja" head) which allowed for precise rotation of the camera to cover a full 360 degree field-of-view. The Canon 70D allows for up to 7 bracketed exposures via the AEB controls. The plates were shot in the RAW (CR2) format, using the kit lens, and stitched together using PTGui software.
After some initial trial runs, where we ironed out the kinks in the whole process, the results were exceptional. For those who may be wondering "why do you want a 32 bit HDR 360 panorama at 10k-16k resolution?" it is used to create realistic lighting and reflections in a 3D/CG software (i.e. Modo or Maya, for example). The 3D scene can be lit entirely by the 360 panoramic image, producing a very convincing result.
At any rate, the Canon 70D delivered terrific results doing something I didn't even foresee when I bought the camera. I will try and upload some of the tests (where the photographic panorama serves as both background and light-source) if I can figure out how to do so on the Amazon site.
EDIT - 11/9/2013: A note to anyone who intends to shoot green screen (for color keyed composites) or do precise color grading in post production: The video output from the 70D is not YCbCr 4:2:2 compression. This is not apparent to the naked eye when viewing the video footage, but it becomes an issue when attempting to work with the footage in a post environment. The firmware update for the Canon 5D addressed this problem by enabling 4:2:2 color output via the HDMI port to an external recording device (I use the Atomos Ninja 2 for this) but currently uncompressed "clean" HDMI is not enabled on the Canon 70D. I have my fingers crossed this will be dealt with in an update to the firmware.
This is not a huge issue unless you intend to do extensive manipulation of your video footage in post production, but it is something to consider with this camera and DSLRs in general. There are workarounds, of course, but that can entail a fair amount of time & effort, particularly when extracting color key mattes (masks) involving fine edge detail or areas of transparency.
That being said, the footage is nevertheless beautiful. And I suspect this technical point should not be an issue for most people considering buying the Canon 70D. The CR2 (camera raw) files are not at all affected by this, it's a factor limited to the HD video.
