> The right amount of compression in a photocopy machine is zero.
This isn't an obvious statement to me. If you've had the misfortune of scanning documents to PDF and getting the 100MB per page files automatically emailed to you then you might see the benefit in all that white space being compressed somehow.
> But what does it mean to “be aware of” compression that may give you a crisp image of some made up document?
This isn't something I said. A good compression system for documents will not change characters in any circumstances.
If you are making an image of a cityscape to illustrate an article it probably doesn't matter what the city looks like. But if the article is about the architecture of the specific city, it probably does, so you need to 'be aware' that the image you are showing people isn't correct, and reduce the compression.
Compression that gives you a blurred image is a trade-off.
But what does it mean to “be aware of” compression that may give you a crisp image of some made up document?