Yes, of course. Remember there are no rules in art. Middle values are fine. It is important that you understand that they are not a particularly dark or light value. They are simply in the middle in terms of value. Sometimes, when we have a lot of middle values, it can be more difficult to see the picture because there is less contrast. Because the value “difference” is minimal, the picture can sometimes feel subdued and less striking. Again, there is nothing inherently incorrect about making a subdued, subtle painting. We just have to understand why our picture feels this way.
