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