What photo resolution should be used on the photographer's website?

Question

HTML

I'm in charge of optimizing a photographer's website. Website loading speed is one of the key search engine ranking factors for organic traffic.
Last year optimized photos for 1280px resolution on the wide side. Technologies are developing rapidly. The main traffic goes through mobile devices, but their screen resolutions are getting larger and larger.
Please advise what resolution to follow for the next year in this situation, in order to balance between the speed of loading the site and the quality of the displayed photos.

Answer 1

As a coder and frontender, I will say this so that you don’t bother too much, use fullhd, compress images, make them links to the original, and use popup or without it. That's the whole secret. If you get very confused, you can use the picture element, on this issue Makeev made a cool video on his channel, google it.

Answer 2

As stated in the comments
All this works fine when loading images using the GD extension, or custom classes on top of it. For example: sanchiz.net/blog/resizing-images-with-php

Answer 3

You can specify the size 1920 with 57% compression jpg will weigh 542kb, you
can specify the size 1200 100% compression jpg will weigh 860+kb.
The difference is almost three times!
- the format should be JPG
- so that the size is not more than 1920 on the larger side (height \ width, as there are different orientations of pictures)
- so that the compression is around 60-80%
And sometimes they push the BMP format instead JPG 4400 pixels, and wonder why the picture weighs 12mb instead of 500kb.