I sold my 40D and bought a 7D. (I already had a 5D MK II). The 7d just did not get used, so I returned it. I still needed a 2nd body so I found a deal on a used 1d MK III. It gets plenty of use, Its much better for my use than the 7D. I do not have the 1d MK IV, I was planning to get one, but the 1D MK III works well for me, except in the ultra high ISO area, I do not use it beyond ISO 3200.


The 1D low light appears to be just a tad better than the 5D MK II, the sensor has the same pixel density.


I have dropped my plans to upgrade from the 1D MK III to the MK IV due to the problems with AF in low light, its something I use a lot on my 5D MK II.


Images from the sensor should crop very well, its the same density as the 5d MK II, and the 5D crops extremely well.





I'd suggest the 5D MK II, but be aware that it is a bit of a shock going to a FF from a 1.6 crop. You will want longer lenses to get the same field of view, unless you are sticking to wide.