I'm making tiny animations in Photoshop, (72dpi greyscale 10cm x 10cm, approx 2 seconds length, filesize around 22k). I then export from Photoshop at the default setting, Quicktime in .mov format.
Ah, a classic example of Photoshop thinking! It's time to think in After Effects.
Forget all about dpi. The concept doesn't exist in AE. Photoshop only utilizes it as a handy guide for common video resolutions, and it's becoming less useful every day. AE deals in PIXELS: the number of horizontal pixels and vertical pixels in a comp. DPI is completely irrelevant.
Here's an example: In Phiotoshop at 400 DPI, a 1-inch x 1-inch image has dimensions of 400x400 pixels. At 100 DPI, a 4-inch x 4-inch image has dimensions of 400x400 pixels. Imported into AE, both images are precisely the same size: 400x400 pixels
And if DPI means, "dots per INCH", it must be tough to work in metric linear measures like centimeters, n'est-ce pas?
I then export from Photoshop at the default setting, Quicktime in .mov format.
The ".mov" file extension simply indicates that the file is a quicktime movie. Quicktime movies are simply media containers. The file can be encoded via a ny number of schemes, called Codecs. Here's a metaphor: an .mov file is a bottle. A bottle can hold many different kinds of liquids: beer, milk, water, juice, gasoline... you get the idea. Those liquids are the codecs.
The codecs of some Quicktime Movies don't work well in After Effects. Your configuration of Photoshop may default to one of the bad ones: we can't tell. But you can -- highlight the problem footage in the project window and look at the information at the very top. The identity of the codec will be revealed there.
Thanks for the reply, I get the pixel / ppi issue, and you're right, after many years of use, my thinking is firmly embedded in Photoshop logic..
In the meantime I've found a solution to this, I have tried exporting as mpeg-4 and that actually seems to work very well for this purpose. I will come back if I run into further problems. Thanks again!