Here is the full list of all 46 Viewfinder achievements. It takes around 5-6 hours to unlock all of the achievements on Windows.
Break the windmill inside the painting
Collect all the camera filters
Find all the planets in chapter 4
Draw using the green pencil
Make a choir of screaming people
Find all the mahjong tiles in chapter 3
Get behind the waterfall
Release all the blueprint Dustins
Ride a balloon
Get multiple jump powerups
Get the jump powerup
Break the cartoon rope bridge
Make the maximum possible number of batteries in the first camera level
Slice a Dustin
Make an army of Dustins
Drop a Dustin off the level
Find all the magnets in chapter 2
Grow the flower to attract a bee
Put down both playing cards
Find all the ducks in chapter 1
Put the three paintings where they belong
Place the recursive photo 15 times
Rewind for a really long time
Complete the third level without touching the battery
Complete all the optional challenge levels
Carve the melon repeatedly
Complete the game
Complete the simulation shutdown sequence
Complete a timer level with only a fraction of a second to spare
Take 100 Photos
Go for a walk in the barcode forest
Ride the train to the final hub world
Complete the picture frame levels in chapter 4
Beat a level in less than 10 seconds!
Complete the illusion levels in chapter 3
Drop a battery onto your head
Break the only teleporter
Take 25 photos
Try duplicating Cait
Get the camera
Get tricked twice in a certain level
Pet Cait
Drop a battery off the level
Place a photo while falling and land on it
Ride the train
Return to the hub world