Believe me, working from life is absolutely an awesome experience than making it solely from a picture. I found it is completely true in a life drawing experience during my recent trip to Kansai, Japan.
When confront with a group of lovely Nara deer which wandering around in the park, I was fortunate to study the comparative anatomy of these creatures as well as the introspective mood in the same time. It was a pleasure to sketch the live deer than working merely from photos.
I remember Richard Schmid had once explained in his book of Alla Prima II that each subject exists in three dimensions in the world while drawing and painting are to create them into a two dimensional depiction like camera does to a photo.
Drawing requires sharp scrutinization in measuring and seeing the relationships among the shapes, and figures out the proportion of each aspect which sometimes could hardly be juggled on a photo. Working from life is indeed offering a good opportunity to find out more than you can acquire from a book or others’ experience sharing that you could never expect.