How to properly apply an effect to an image in Photoshop?

Question

Image processing

Good afternoon.
There is an original image:

On one of the sites I saw how a filter was applied to it, and I really liked the result.
I can't figure out how it's implemented. If you can give a detailed answer or a link to the tutorial, I will be very grateful.

Answer 1

The easiest way is to determine which will be the lightest and darkest, set them and go Image - Adjustments - Gradient Map
Then you can slightly increase the contrast and so on.

Answer 2

I'm far from an expert, but I think it's called "sepia".
A Google search yields many tricks, take your pick.

Answer 3

Sepia Effect in Photoshop