There are a total of 10 Optional Photos that you will need to find in order to obtain this. You can "Play Episodes" and select specific parts of the Episode in order to find the missing optional photos through
collectibles mode. There is also a counter on this screen to help you figure it out.
The optional collectible locations can be seen below:
[0:17] - Optional Photo #1
[0:39] - Optional Photo #2
[1:04] - Optional Photo #3
[2:06] - Optional Photo #4
[2:36] - Optional Photo #5
[3:00] - Optional Photo #6
[3:42] - Optional Photo #7
[4:26] - Optional Photo #8
[5:15] - Optional Photo #9
[5:43] - Optional Photo #10