With all these examples, I'd ask you to remember that you're looking at 'before' and 'after' side by side, so you know where to look for the repairs! And, these pictures for the web are saved as JPGs to shrink their size, so some of the quality is lost.

This first one is moderately old, but taken with a really poor quality camera (pin-hole lens?), and I suspect, poor film and/or wrongly exposed. The image isn't in focus anywhere, the highlights have burnt out, the shadows are dense black. There are limits to what can be done, but I hope you'll agree it has been improved. I thought any further changes would spoil it.

The original:

The updated:

Next a 1950's vintage, the original has reasonable contrast, but the photo is very damaged and very soft focus. The enhancement has repaired the damage, increased the tonal range slightly and slightly improved the focus (overdoing the sharpening makes the picture go very grainy).

The original:

The edited version:

A 1920s portrait, slightly damaged, the original has very good definition, but poor contrast.

The original:

The edited version:

Want to turn a bit of a grey day into a sunny day? I like this picture, but I feel the grey appearance of the sky (even though in reality it was a sunny day, with blue sky & white clouds) spoils it a bit.

So I added a new sky. This is a 'real' sky, but from a different day.

Or you'd like to pull out a particular part of a photo and lose the rest. In this example, some of the clutter has been removed to enhance the subject.