Your regular printer, like mine, presumably puts down a line of melted plastic material with an extruder, bit by bit, so the print time is guided by complexity as well as size.

Resin printers, basically, are stereolithographic. They:

- dip the build plate (upside down) into a thin tray of resin

- push it all the way onto onto a screen at the bottom of the tray

- blast that screen with UV through a translucent LCD display that contains a mask image of the current "slice" of the whole plate, enough that the thin layer of resin partly cures

- lift the plate out of the resin so it peels off the screen and the resin replenishes below it

- repeat, with the next slice.

- then the whole model is taken out by hand, washed off, blasted with UV light to completely cure it, and the (more or less inevitable) supports snipped off.

So instead of printing line by line, the entire plate prints layer by layer — a small print takes (approximately) the same time as a full plate.

There are several big differences, notably that it is single-colour, much higher resolution, the various peel/adhesion forces are managed differently, larger parts need to be hollow with a vent so uncured resin drains out, most resin prints are quite brittle, and the whole process is traditionally really rather cytotoxic.

There are eco resins, tough resins, and printers that do a better job of not being chemically evil; this is one.

I've stayed away from it, because it's not the kind of printing I need (for all except one part that I might end up subcontracting) and because it is chemically nastier than b/w darkroom printing, which until now has been about my limit of risk.

The above is a bit of an oversimplification but it covers the main differences I think (happy to have corrections/additional comments)

https://formlabs.com/uk/blog/ultimate-guide-to-stereolithogr...