For my animations, the frames have to be rendered at a final resolution of 400 dpi at 8.25" x 4.25" (3300 pixels x 1700 pixels). All I do is render with the document size at 3300 x 1700 which comes out to 45.83" x 23.61" (at 72 dpi). I then adjust the image in PhotoShop by making the dpi 400 and the size 8.25" x 4.25". Basically, the picture doesn't change because it is still only 3300 x 1700. Does this make sense? PhotoShop makes it easy to do with the Actions feature. You just record your steps in the action feature, then use it again for multiple frames.