The Good The Canon EOS 6D delivers the photo and video quality you expect from a full-frame sensor, in a well-designed and relatively lightweight body.
The Bad While the camera has nice extra features, like Wi-Fi and GPS support, it's missing some basics for the price like on-camera flash, multiple card slots, and a 100 percent-coverage viewfinder.
The Bottom Line The photo quality you get from the EOS 6D makes it well worth the upgrade over a consumer APS-C model, but between this and comparable or higher-end models it's a less obvious choice.
A lovely camera, but watch the trade-offs
In some respects, it's hard to tell who Canon's targeting with the EOS 6D, its "budget" full-frame camera. It's got some fairly consumer-y features and specifications. GPS? Check. Built-in Wi-Fi? Check. Single SD card slot? Check. Viewfinder with less than 100 percent coverage? Check. Wimpy autofocus system? Check. On the other hand, it's missing things like a built-in flash that you'd expect in a nonpro camera.
It's not that the 6D isn't a really nice camera -- I happen to like it a lot. It's got great photo and good video quality, relatively fluid operational design with a soft shutter action, and a solid (but not weatherproof) build. But ultimately I find it a confusing buy and just a tiny bit of a letdown.
I'm extremely impressed with the EOS 6D's photo quality; it delivers excellent JPEG processing and noise reduction, great dynamic range and tonal quality, and accurate colors if you change the defaults. JPEG shots are relatively clean through ISO 800 and still quite good through ISO 1600, even for large prints. And depending upon scene content and usage, you could probably get away with it all the way up through ISO 12800. By ISO 1600 I see noticeable advantages to shooting raw over JPEG for noise processing; Canon favors noise suppression over detail preservation, and I'm willing to accept a little grain. All of that's tweakable in the camera, of course, if you're dead set on JPEGs.