I am trying to simulate a traditional animation look on an AE rigged character animation. It is a 25 fps comp and I need to render every second frame or 12 fps, but want to retain the length of the comp. When I change the render settings to only render 12 frames the animation looks great but it only renders every second frame of the camera move, and there's too much juddering.
how about changing the composition settings to 12fps? you don't have to render it, you can preview it and only then decide if you want to render.
about camera move - you don't want the camera to play at 12fps. one way to do this is work with 2 comps. the main comp will be 25 fps, inside there will be a precomp of 12fps. the stop motion feel will be inside that comp, but the camera move will be in the 25fps. you need to check "preserve frame rate when nested" in the 12fps precomp so you can play 12fps inside a 25fps comp.
another way to go is use the posterize time effect and set it to 12 fps for the precomp (while working in the 25fps comp). if there is an expression somewhere that does what you ask, I Imagine it will be posterize time and it maybe needs to work on time remapping, so you would have to precomp anyway.
Update: Now I see that Dear Walter answered you question here: CreativeCOW so guess this actually works on layers and great way to speed up your workflow. so thank you and thanks to Walter. Great to know!
The lower the frame rate the more you get judder. At 12 fps your critical panning speeds are even more critical. There are only two solutions, More motion blur or use a pan or camera move speed that does not judder.