i am a 'professional photographer' in a mountainous wintry environment without salted roads
my accord isnt exactly show n shine, though i did finally fix the heater!
will detail in modzzz list!
also, my digital camera was flogged by some little dogs
i have a few film cameras though so im not out of the running yet!
anyway some input form my printing experiences:
4MP sounds about right for an a4-ish sized calendar in my inkjetting experience, but the final quality depends a lot on the printer and the paper, rather than the source resolution.
file formats might also be an issue, because most of us are storing and submitting JPEGS, which can have anything from quite clean compression to really nasty artifacts that look like pizza, depending on the camera, settings and individual scene elements. this is generally unnoticeable on the screen but hardcopy has more depth and dynamic range and thus less mercy, and once the images have been selected, it might be impossible to re-shoot for print.
so i advise photographers to remember this is going ultimately on paper and perhaps investigate what other settings your camera has for file formats, IE lossless like TIFF. big fancy cameras generally do 'RAW' now, but thats a bit different again and comes with its own problems for the poor guy [2ndgenguy?] who has to put it all together and proof it.
colour management is the final headache when it comes to printing, and basically means you dont get what you expected and saw on your monitor. you'd be surprised how bad and expensive the results can be and its easy to have some screw up that makes all your reds maroon, your blacks grey-blue and greens fluorescent.
i dunno whos handling this but if you're emailing the master file off and getting a box of calendars back, its a risk.