So, right now I have a 40D, I really have no complaints about the performance of the autofocus or burst fire rate, and the image quality is fine when there is enough light. I do find the colors look a little flat straight out of the camera, and the dynamic range is lacking compared to what I've seen out of the newer stuff out there. Been shooting with it for 7 years, and this is the first time I've felt like my technology is holding me back. I've got some decent glass..(27-70 and 70-200 2.8 L zooms and a 50 1.4 prime) I mostly shoot vacation stuff, family, some portraits, some street photography, and lately some bicycle racing. I mostly shoot cyclocross, because that's when I'm in the environment with enough time to shoot (ie not racing myself the whole time i'm at the race) in CX the speeds are pretty low even the pros are in the low 20mph range, and the course is fairly predictable (riding between taped of segments). Having found no shortcomings in the AF of my 40d, I've been leaning towards a 6D, so I can get a significant bump in image quality, and gain some modern functionality (GPS tagging would be nice because the races are all over the place). But there's the nagging "sports" qualifier there, and the 7Dii has framerateand autofocus in spades, but I'm not too sure that it'd be enough of a boost to image quality to justify the purchase.
tl;dr
have a 40d, shoot predictable sports, already have nice glass
want a 6D for best image quality/$
7Dii is best sports shooter in my budget
which one to buy?
tl;dr
have a 40d, shoot predictable sports, already have nice glass
want a 6D for best image quality/$
7Dii is best sports shooter in my budget
which one to buy?