tiff help

I am no graphic designer, but can do enough basics to layout a 32 page quarterly magazine. Quark is fairly simple and I can do the basics with Photoshop. I have a question about the tiff format. My printer guy says I need to change all photos into CMYK and save them as a tiff. When I take a 853kb file and save it as a tiff the size goes to 12mb. Usually I don't worry about it, but this issue our members are submitting photos and I have a lot to change and put in. The size of the magazine file will be ridiculous. Am I doing something wrong?

what is the resolution of these tiff files? Over 300 dpi is overkill and you really only need that much resolution if you are printing above 150 linescreen.

Do you know what "linescreen" your printer is using to produce the magazine?
linescreen multiplied by 1.414 equals minimum printing resolution.

You will get a heavier file using the tif format but it is the way to go.