You can't really teach depths, only things you need to know really are:
  • To Understand Depth
  • Ways To Add Depth


Im not sure if i am right and i doubt this will be a technical explanation but ill give it my best. Depth is similar to contrast, view an image and turn down the contrast and it will seem boring and bland, turn up the contrast (not to high) and it will jump to life. When it gives you the impression that things are on a different level to each other than can be depth to, not in the 3D sense.

As i dont do graphics anymore im a bit rusty, but the main ways i increased depth was changing colours (only works at times) but the main method i used was a brightness and contrast layer, and sometimes a level setting. These are im sure, the easy way and dont have half as good effects as the 'proper' way to do so but thats my view on it

Hope it helped.

Ben