Originally posted by asahijock It sounds from what you have said that had it been the 645Nii v the K1 this might have been the "game changer" in terms of which to buy.
The Pentax645n lacks mirror lock up features of the 645 NII. There are some who think this is a
minor difference as the 645N has an extremely well damped mirror mechanism - for a majority of users the lack of MLU would go unnoticed, but if you work with long lenses 200mm+ in the 1/125th~1s shutter speed range, MLU can make a observable difference. Also the 645NII is more likely to be in good condition as it is a newer camera and its body finish is less likely to chip.