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