What the picture must have in common with reality in order to be able to represent it after is manner - rightly or falsely - is its form of representation.
2.171 The picture can represent every reality whose form it has.
The spatial picture, everything spatial, the coloured, everything coloured, etc.
2.172 The picture, however, cannot represent its form of representation; it shows it forth.
2.173 The picture represents its object from without (its standpoint is its form of representation), therefore the picture represents its object rightly or falsely.
2.174 But the picture cannot place itself outside of its form of representation.