How to cite a figure that has been already modified from another source?

Question

I am wondering how to cite a figure that has already been modified from another source. Normally one should get the original figure from the original source, but there are cases when that is not possible or difficult.

Let's say that we find a figure A in source 1. Figure A is a modified version of figure B from another source 2.

So in source 1 figure A it says in its figure text:

...modified after [2].

Also I am wondering how to cite correctly when I want to modify the already modified figure? Saying modified after again seems quite silly:

modified after [1] which is modified after [2].

In addition one should include "with permission", but the following sounds wrong since it appears as if we have gotten "permission to modify":

modified with permission from [1].

This last example raises the question: does one have to ask for permission to modify a figure in addition to reproducing. Some organizations explicitly tell that no figures may be modified.

So my guess is that it should be formulated as:

reused with permission and modified after [1].

But this last I can't remember having seen any example of in actual academic papers. What would be the correct approach here?

Answer 1

"Reused with permission and modified after [1]." sounds good to me. It will also depend on copyright, which some journals require specifying in the figure caption. Whether the copyright allows re-use and modification is of course key.

Answer 2

I'd say something like "originally from [2], modified in [1], and further modified here"; it's longer than I'd like, but it gives appropriate credit to everyone involved, and it helps to prevent people from being blamed for what the modifiers later did to their work.