Keying a painting deals mainly with value [black and white], although it can also deal with color. But for now, I'm only going to discuss it in terms of value. Basically, keying a painting is determining which sets of values you are going to use throughout your work.
Here is a value scale consisting of 9 tones ranging from black to white. This is just one that I made myself, I'm sure there are others out there with 10 tones or more but that's alright, I think 9 is enough to demonstrate this idea. [And since there is an odd number of tones, that gives us a middle grey.]
For the most part landscape paintings are usually painted in a higher key [not always the case though], especially from artists that paint outdoors or plein air. You may be wondering what the difference is between high key and low key? High key uses mainly lighter values while low key uses mostly darker values. I can hear the questions coming in now - "Can a painting in a high key also use a very low [dark] value?" Of course it can. High key just means that the painting is mostly consumed or dominated with lighter values and a little of darker values in shadows and other areas. Also, the same is said for a low key painting with light values.
It is up to you to determine which value ranges you are going to use in your paintings. There are no rules or limitations - you are the artist, so it is your decision. Just think of it as another part of the design process - no different than choosing your colors, composition and subject matter. In my latest post about not using photo references, I stated that nature doesn't often give you a good design or composition, therefore you have to move things around and manipulate. Same with using keys. Don't let nature decide what goes onto your canvas. Play around with values and knock down the lights a bit if you don't want a super light painting or composition. It's something I'm still working on myself and learning to be aware of when I paint.
Here are some ways you can use value in your work. Don't over-think or become too worried about it - it is just a good idea to be aware of how to key a painting and to know which range of values you are using since different situations, times of day and moods call for different sets of values.
Below is some work from artists that I enjoy and I also show in the bottom left-hand corner the range of values used in their paintings.
|Sylvester Phelps Hodgdon|