From my pt of view, it is recommended to take it asap. When he can crawl, he don't have patience to stay long for one place but will keep on looking for and exploring his new object.
Last time I took him to take photo in Studio123, I firstly let him to sit down on the mat, without 5 seconds...he starts to crawl...then I took him again..just 2 seconds...he continue to crawl...with this incident happened for several times, he didn't like and started to cry..Finally I only took ~4x photo with 4 different types using 1.5 hours.