My passion is wildlife photography and my prime lens is the 100-400 4.5-5.6 L IS. I often have to do a significant amount of cropping even at 400mm in order to get useable images. The more I crop the more I have to contend with noise.
My two bodies are a 7D and a 5D Mark iii. Each has its advantages and I use both of them a lot. The 7D obviously gives me meaningfully greater reach. But, for me, it produces noisier images than the Mark iii. So much so that I generally shoot with considerably lower ISO on the 7D than on the Mark iii. The 7D also has a much slower, and for me, considerably less accurate autofocus than the Mark iii. I get far more blurry and useless photos with my 7D.
I've wound up using the 7D only at times where I really need the extra reach, where the lighting is bright, and where I'm not too worried about objects in motion. For all other shoots it's my Mark iii.
+1. Exactly my experience. And, in practice the higher IQ and lower noise of the 5D III more than makes up for the loss of crop factor.
« Last Edit: February 03, 2013, 10:56:43 AM by AlanF »
5DS R, 7D II, EOS-M, Powershot G3 X, 300/2.8 II, 1.4xTC III, 2xTC III, EF 1.8 STM, EF 70-200/4 IS, EF 24-105, 15-85, 100-400 II, Sigma 10-20, Sigma 150-600mm C, EOS-M 18-55, f/2 22, 11-22