Before there was photoshop....

[Detroit Stylin]

http://fstoppers.com/pics-manipulate...d-after-images

[Jimaz]

I'd bet they used some clever masking to make those images.

You can use masking in Microsoft Paint to manually make autostereograms. It's delicate, tedious work but it can be done.

[Zacha341]

Interesting site! You have to have a great deal of talent and time to retouch and clone things out manually with paint and tints like that.

[old guy]

Back in the 70's I worked at a photography studio. I used to spend about 30 hours a week during certain times of the year in a darkroom removing pimples from school kids faces on negatives with a tiny brush. To this day, when I see a kid with acne I think, hmm, there's about 5 - 8 minutes work.
I love photoshop.