How to make a scanned pencil illustration darker?

Question

Design

I'm trying to darken a scanned illustration with a pencil in Photoshop through contrast, brightness, etc. - in the preview it actually becomes darker, and after applying it returns to its original brightness. Scanned most likely in black and white, pdf format, translated into a jeep.

Answer 1

Firstly, look at what bit depth and what color space it is in now, apparently in one-bit b/w. Convert to RGB and put some of the effects of a slight blur, after which it will be possible to work with contrast. It is better to work with the original, without details it is difficult to advise something.