I always use a black and white copy of the subject photo as reference. The one I used to draw from for this painting was approximately 9" X 5". Not all that big. I started drawing with my paper on an easel, vertical, so it would be easier to draw accurately. Then, when the outline looked fairly decent, I moved everything to a table. From then on, I used the image on my computer screen as reference. You can zoom in to see details.
Today, it was time to work on the man's shirt. I had no idea he was wearing a plaid shirt! The black & white photo reference just showed hints of plaid, which I completely missed. Well, he has a plaid shirt. Interesting challenge.