The Problems With Chemical-Based Photography

If your grain size is 50 microns, then you can't render anything that's projected onto your screen if it's smaller than 50 microns. The projected size of an image on your plate depends on the lenses you're using and the position relative to the plate. If you have a 50 micron grain size, you might be able to pick up more fine detail in a photo than if you were using 100 micron grains. But once again, these aren't exactly pixels. This is more a gross generalization of resolution.