If your project is relatively simple, it doesn't matter too much if the colours are exactly aligned, and you need fewer than 500 copies, you can get away with silver masters. Be sure that you ask to see the plates. Some unscrupulous printers will substitute electrostatic plates and call them silver masters. A silver master plate is white on one side and black on the other. The image is silver.
Electrostatic plates are purple.
They do not provide satisfactory results under any conditions. I used PhotoShop for my graphics, and then put together my newsletter in PageMaker. Now the printer says that he can't use the file, because the colours are unprintable. There's a big difference between colours that a computer monitor sees and colours that can be reproduced on a printing press. Your computer monitor makes colours with light, while inks use pigment.