now then,
in the Batch Rendering settings:
Image File Output¬

Frame/Animation Extention:¬

ie: frame.#.(Tiff)
if you select the: Frame.tiff.#: (Option)
Photoshop, etc, will not reckonise the frames' extention file format

If rendering a sequence of frames substituting the # for 01,02 etc,
maya will insert the numbers per frame for you.
and the animation will be viewable as stills.
see the attached...
Hope this helps?

later
Grocer.