The one thing that bothers me more than it should, it's than the new photos are not taken at the same angle and/or distance than the original ones, making the comparison worse than it could.
You should keep in mind that getting the lens focal length right is very important here, and it's something that's rather hard to do if you don't know what the original focal length and film size was.
It shouldn't be that hard if you have the original photo with you when taking the new picture. Simply look at the proportion of near and far objects and walk back and forth until they are the same as in the old picture.
I completely agree. I find the sliders to be frustrating and detract from the experience of taking in the changes in their entirety. We aren't doing a pixel by pixel comparison so the UI shouldn't treat it that way.
I recall a talk or possibly HN post I saw once, where they developed some software to warp photos like this to account for camera position and focal length.
