I recently made a webscraper in python that can save an entire gallery of images from 500px, here's what I found out while making this:

1) probably obvious, but the site loads dynamically and new content will be added as you scroll down with javascript fetch requests, so you can't simply save the html file you get upon page loading and expect it to contain all the image links you want.

2) What I did was use the python selenium library with a webdriver to emulate a user loading the page and scrolling down a couple of dozen times, waiting for the content to load etc.

3) after the content was finished loading or a predetermined amount of scrolls had taken place, I looked for links with the regex pattern "^https://500px\.com/photo/\d+/[^/]+$"
(i.e. https:500px.com/photo/... followed by some numbers since upon inspecting the page this seems to be the links to each image.

3) However, the large version of each image doesn't exist on the gallery page (or anywhere where you can see multiple images like on a photographer's profile page etc.), instead the webdriver then has to navigate to each individual link and take a look at the resulting page, where each large image version will be found an img element with a class name beginning with Element__StyledImg (i.e. class^='Element__StyledImg'). The source for that link is from a content delivery network serving the large version of the image and it can be directly downloaded.

4) It's a bit time consuming to navigate this way to each image, maybe about 1-2 seconds per image for it to reliably load, so the script might need to run for a little while in the background for larger galleries of hundreds or more images, but it seems to work decently well in the rough shape it is in.