I am looking for some advice about upgrading my current camera. Here's what I have at the moment:
Canon 550d, 50mm f1.4, 70-200 f4 L IS, 430EX II flash, Sigma 17-50 f2.8 OS
I am interested primarily in portraits / people (maybe 80%), about 3/4 of which is of my 3 year old daughter. The rest is mostly travel. I do not do any wildlife, sports etc, that have special requirements. A 3 year old is a fairly high-speed object with erratic movement though.
There are two reasons for upgrading. The first is that the autofocus of the 550d struggles with fast moving subjects (i.e. children). The second (less important) reason is that low light performance of the camera could be better. I am generally happy up to about ISO 800, but after that it degrades rapidly. I have also found the performance of the 17-50 disappointing, but I think this is because the AF system is particularly ill-behaved with this lens; the keeper rate is lower (maybe 60%), and there is fairly consistent back-focus which I can't correct. I generally do not print anything larger than 8x10. I will occasionally shoot video, but nothing serious.
I am trying to decide between the 7D and a 5D III. In the 7D case, I would stick with the 17-50 and hope for improved performance given the better AF system and AFMA. In the 5d III case, I would sell the 17-50 and replace it with a 24-105 f4. I live in central Europe and hope to buy something on my next trip to the US in about a month (delivered to a friend's house to collect). For this reason, the 6d and 7d II / 70d (if they ever appear) are not options. Prices here are much higher, and I will not be back to the US for at least a year after this trip. I also tried a Nikon d600, but really didn't like the ergonomics, plus I don't want to dump everything and start again.
The 5d III offers everything I want of course and is FF, but the price is very high and the camera is basically overkill for my purposes. I don't care so much about the super robust build, dual card slots etc, and would gladly pay less to give up these features. In this case I only have sufficient budget to buy the kit with the 24-105, which would leave me with a 3 lens configuration (50 1.4, 24-105 f4 and 70-200 f4), which will not actually be taking advantage of some of the camera's AF capability, and moving from the 17-50 f2.8 to the 24-105 f4 partially offsets the ISO improvements. I can get the 5dIII + 24-105 kit for about 3750 USD. That's not from an authorised dealer, but I don't care because I won't be in the US to return it anyway if it breaks. I can recover ~450 USD by selling the 17-50 in this case, so say 3300 USD net.
The 7d is maybe a more logical choice for me, since it is a lot cheaper and addresses the more important AF concern. However, I am not keen on buying something that is about to be replaced by a newer model. It also has the same sensor as my 550d, so presumably the same low-light performance. The video capability is somewhat worse. Refurbs go for about 1200 USD on occasion. Given that that is about 2000 USD cheaper than the 5d III option, I would also consider buying some additional lenses; probably the 24-105 f4 anyway (I realize not a popular crop choice, but the range I like most on crop), and an 85 f1.8 or 100 f2. Even with those two added to the purchase, the total cost is several hundred dollars lower.
I'm grateful for any advice or other ideas.