The client is happy with the photo shoot for the portrait commission. Do you really then want to do an on-site head study in less than an hour possibly flying by the seat of your artistic pants? What happens if you have a bad day? All could be lost with the client.
I personally think it is called 'doing your art homework'. I see so much painting a face that I don't see through the camera lense which so intrigues me - and this will aid my final portrait.
I am eternally grateful to my mentor Mr. Everett Raymond Kinstler, N.A., who has made me see the value of this discipline. It was a big jump for me in my portrait work when I started to request a head study at the portrait shoot.
This one is my drawing for the day yesterday. I sat the client by a window and painted this in about 55 minutes.