This picture is actually a lot more impressive than it looks, because there were no color cameras available when it was taken. Instead, he had to take three different pictures, using three different color filters like RGB, and then combine them to make it color.

From one source:

Prokudin-Gorsky's camera design required a camera operator to take three individual negatives after each other. Given that Prokudin-Gorsky is seen posing in the image, it is more likely that one of his assistants took the picture.

And another

To this day, nobody knows exactly what camera Prokudin-Gorsky used, as no documentation of his equipment is known to exist, but it was likely a large wooden camera with a special holder for a sliding glass negative plate, taking three sequential monochrome photographs, each through a different coloured filter.