Dodge and burn (D&B) technique allows us localy lighten or darken specific areas of images to reach desired result. Usually it's used in a meaning of beautyfying human skin and that's the way I'll try to explain.
Way no.1 - using the basic tools
In a tool palette there are two specific tools called dodge tool and burn tool. Dodging lighten up the image and burning darken the image. These tools are very easy to use. Using the strenght slider you may reach the desired amount of dodgin and burning. I do not use these tools for regular retouch because it's simply destructive. You have to apply these tools directly to an image. But yes, I do use these tools on masks. This way it becomes really handy helper. Especially in combination with channels it becomes very practical. For example separating dark hair from lighter background takes just a while.
Way no.2 - using the gray layer
Using blending modes allows us to reach the more control above the image. Using a soft light (or hard light blending mode) on a neutral gray layer has a reason. We can reach the same effect using a blank layer but once you start switching between normal and soft/hard light mode (or other, depending on a decision) it allows you to see better where you painted white or black. Seeing it in a normal blending mode can give you a great idea how much you dodged and burned the image and where.
I do believe some of you may become confused. Blending modes like soft light or hard light interact with layers bellow in the meaning of contrast which affects colors and luminosity of tones. This means if you paint black in a new layer, blend it to a soft light, you'll darken the image (you increase the contrast and darken the image). Because black, white and shades of gray are neutral colors, they do not change a color of layer bellow but only contrast. Color will be affected just in a minor way. If you paint red you'll get the change of luminosity but you get the tint as well. These blending modes affects everything but the neutral gray. Principle is, you create new layer, fill it with neutral gray and blend it to a soft/hard light which means neutral gray won't be displayed but once you change blending mode to normal, you can clearly see where you painted. Then you paint with black, white or shades of gray to darken or lighten specific areas. This was the method we used before there were adjustment layers. It's not bad at all but these days there are more ways to have an image under control.
Way no.3 - using adjustment layers
If you heavily lighten or darken image, there is a color change appearing. Instead of using gray layer you can apply contrast using an adjustment layer. You can use levels, curves or exposure. I like using curves the most. It does the same as a gray layer but there's an advantage. You can blend it to a luminosity mode which means the colors stay the same but only luminosity changes. There is no tint at all. This solution may be enough if there is no radical dodge and burn but sometimes you need to do it. Using an adjustment layer is great because you paint white on a black mask to reveal the effect of lightening or darkening image (it means you do not use single layer for both - lightening and darkening an image but two separated layers, one for lights and the other for shadows only). Once you have this mask you can load it (CTRL + click on mask) and create another adjustment layer to change the tone of undesired color tint of heavily dodged and burned areas. You do not need to paint another mask, you just copy a recent one.
Using a control set of layers
If you want to see where to paint the light I reccomend to create another set of layers for control. One simply black and white adjustment layer and one or more layers for increasing a contrast ( I usually use curves or brightness and contrast layer). Turning image BW means colors won't distract your eyes. Increasing contrast helps you find out where are problematic areas. Once you are done you'll delete these control layers.
Using dodge and burn needs some of practice. I usually go from the bigger blemishes to smaller and end up with the smallest details. The last action is painting fake lights and shadows.
Everyone has a different eye so everyones D&B technique looks a bit different. You can use it to reach very natural look or something extra retouched like Dior commercials but basic principles stay the same. I can only reccomend to zoom in and out once in a while and hide a "eye help" set of layers times from times to stay informed about whole canvas.
My way is using adjustment layers of curves, then I invert the mask and paint with low opacity white or black brush. I usually use brush with 5-8% opacity and brush is soft. Size of brush varies from 2px brush to several hundreds of pixels. That's very individual.
You may find this article helpful - Myths about dodge and burn
Well, I hope I explained you this technique enough, I yet plan to do a video demonstration of using this technique once I shoot something suitable so you can use it by yourself with no further questions. Wishing you a good luck with you images and stay tuned.
Lucie Kout
Chanels is limited. I love retouching but mostly get accused of overdoing every time.
A video would be great
just stay tunned and read following articles, there may be another useful tips for you!
regards
Lucie
P.S. I believe there are lots of people who wants to share the knowledge, we just usually don´t know what keywords to search :) good luck with your improovement