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