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