I have a Nikon D7200 and recently tried a new project, 360 degree product photography using a homemade turntable and shooting a product a friend of mine makes, carbon fibre horse saddles.
I had the camera mounted on a very sturdy Benro tripod and used an external shutter release, however on all the tests i did i came across a puzzling problem.
It appears that the mirror (maybe) is moving slightly and altering the vertical postion of the shot, compare the two shots below.
If i looked thru the viewfinder whilst taking the shots i could actually see the movement, it wasn't a 'fast' drop, more a slow 1/4" sec slide down.
Can anyone suggest a reason for this and how to fix it, in the end i post-processed the dozen or so shots that had dropped and aligned them as best i could, the results are here (yes, i forgot to polish the acrylic, but it was just a proof of concept to show my friend).