According to the Mark IV manual I just downloaded, on p 35 it states the battery life is good for approximately 1500 shots!! In my current Mark III bodies I get about 4 times as many pictures from a battery!! Do you suppose this is correct, I can not imagine there would be such a significant decrease in battery life with this new model?
The 1D3 is rated at 2200 shots, so if you're getting 2.5-3X as many from the Mk III, you'll probably get similar from the Mk IV. Figure, at your usage, 4500-5000 shots on a charge.
I think that the Mk IV uses more energy due to the brighter display and the increased processing needed for the larger files.
.. Really? Only 1500 shots this monster ?
??
