Summary: I have over 3 years and 200,000+ photos worth of use out of this camera. It is great for sports, excellent image quality at high ISO. 6400 is very usable even for prints. 12,800 is where it gets a but shaky. 102,400 ISO is unusable for publication, but has a cool artistic effect if youre into that.
Summary: I purchased one of these amazing professional level DSLR's recently along with the new 7D Mark II to test them side by side and then decide which to keep. In my humble opinion the 1D Mark IV is better in every way except it's heavier and the video autofocus of the 7DII is better.
1D MK IV is in a league of its own, in a class by itself
Kenneth G. Nielsen, Amazon
1 November 2014
Summary: Top of the line professional camera. When you study the results on Canon forums you begin to see that it takes a good photographer to take good pictures, then comes the glass, the all-important lenses that yield the best results begin to show that this is the next important area that leads to taking...
Summary: Canon EOS 1D Mark IV 16 Megapixels The 16MP, $4,800 Canon EOS1D Mark IV is the first and only APS-sensor camera to claim a maximum ISO of 102,400, and has a recommended top ISO of 1320. It has a signal to noise ratio of 41.4 dB at ISO 100, and doesn't dip below 30 dB until after ISO 1600.
Summary: *** UPDATE, 2/21/2012: I sold my 7D bodies to upgrade to another Mark IV. The 7D is great, but the Mark IV is vastly superior on nearly all fronts. *** Just like with the Canon EOS 7D, Canon took a serious look at their line-up and listened closely to their customers as well as market trends.
Summary: There is a ton of info out there on this camera and I just want to echo most peoples findings. The pluses: Autofocus system is a huge win! I had a 5d mark ii and a 7d before this camera. I still have the 5d mark ii and the 1d mark IV destroys the 5d as far as autofocus goes.