Just tested this once more with 2 different copters, 3 cams and 2 St16. On the desk, no need to be up in the air.
Both St16 have this problem. Nothing to do with the copter or cam (2x E10t, 1xE90).
With low TX voltage it starts shaking around tilt axis. Can see it in the RC monitor as well...
Hey, just realised I have the exact same thing when ST16s battery gets below 35% or so.
The cam (E10t) makes tiny up and down movements. No shaking if it is fully straight or fully down.
Luckily I remembered your post here. Left the drone switched on and inserted a fresh battery to the ST16s...
I am also using the H520 with E90, amongst other cameras.
From my limited experience I can recommend Microsoft Image Composite Editor (ICE). Did two projects with it. Dead simple to use and worked fine for me.
Sorry, Too little experience with it. The experts here should advise you.
Pix4D and DD trials looked fully operational to me though.
What is that job, you need to do? If it is 2D photostich only, you could use other free software as well.
DPI is totally irrelevant in this regard. A digital image has no DPI. The relevant property is how many pixels the image has.
DPI becomes relevant if you want to print. The bigger your print-out of the same digital image is, the less dpi you will have as the same number of dots (pixels)...