They can act both as demonstrative pronouns or as demonstrative determiners. If acting as a demonstrative pronoun, they do not modify a noun. For example: "is dit een oude foto?" Here, "dit" is a demonstrative pronoun. If acting as a demonstrative determiner, the modify a noun and thus must agree in gender with the noun they modify. For example: "is deze foto een oude foto?" In this last example, "deze" is being used as a determiner, that is, as a "pointer", it is specifying which photograph you are referring to. As such, it must agree with the noun it's " specifying". In this case, "foto". As " foto" is a "de-woord", you have to use "deze".
So, do I understand correctly, "een foto" is one type, a subcategory, of "een afbeelding"?
If so, would it be common in Dutch to link a subcategory to a main category with "or"? It isn't quite how one would do it in English, but it makes a certain amount of sense - sort of like "Are these images generally, or specifically photos?"
In short, to state that "these/those" are identical to something, "dit/dat" are used ( with zijn or other linking verbs); to state that "these/those" have certain properties, i.e. being described by adj., "deze/die" are used.
Hope this helps :)
I'm aware of this construction, but I'm confused due to the lack of an adjective to warrant this construction. I think after reading your explanation though, I've come to conclusion that the use of an adjective is being implied via "dit", but there is no adjective actually present in the sentence itself. Am I right, or am I a long way from the target? (<.>)