def _unbin(tile_data, factor):
    """
    tile_data should have shape (num_frames, y, x)
    """
    s = tile_data.shape
    tile_data = tile_data.reshape((s[0], s[1], 1, s[2]))
    unbinned = tile_data.repeat(factor, axis=2)
    return unbinned.reshape((s[0], factor * s[1], s[2]))
