Imprimatura on the Canvas

I am experimenting with a technique of creating the imprimatura on the canvas 'as you go' rather than pre-prepared. Also having a different imprimatura in different parts of the canvas. There seems to me to be a warm underlying light in a rainy English winters day. So I tried a warm imprimatura in the mud area.

PS The photo of my painting is not accurate. I took it hastily under interior warm light. The actual colors are much truer to nature. But of course even though the photo is warmer, all of the internal relationships are accurately picked up by the camera.