Here's a post for tonight. This is from lesson 2 from the Fundamentals of Realism course on Schoolism.com.
I was tasked with making a block in of a reference image, and then add increasingly more detail. The challenge was that the block in had to be larger than the original.
Afterwards when I was finished I wanted to see if I could use my new found understanding of imaginary guidelines, plumb lines, angles and such to guide my painting, and it really worked!
The colours are muddy, sure, but I was able to get all the shapes right thanks to the guide! Really worthwhile lesson!