There are a total of 6 Optional Collectibles 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:
[0:03] - Draw a Sketch
[1:00] - Collectible #1
[2:25] - Collectible #2
[3:00] - Collectible #3
[4:13] - Collectible #4
[5:07] - Collectible #5
[6:40] - Collectible #6
You will also unlock the following trophies along the way:https://www.trueachievements.com/a260740/the-dharma-bums-ach...https://www.trueachievements.com/a260741/train-of-thought-ac...https://www.trueachievements.com/a260742/zero-hugs-given-ach...https://www.trueachievements.com/a260743/green-thumbs-achiev...https://www.trueachievements.com/a260744/dancing-days-achiev...https://www.trueachievements.com/a260745/one-of-us-achieveme...