poster sized prints
I work with 20 by 30 as my standard print and file size. A 7 megapixel camera is sufficient though not ideal...the ideal is a camera beyond any pixel count one can imagine. That is the key. Infinite res is what one wants but what one can afford is a different issue but let me say that the way one should determine what pixel count is necessary is decidedly NOT to simply divide pixels per side by the print res such as 150 or 240 or whatever. This simplistic and common method does not consider that modern software both available either in the printer itself or in computer software allows for essential re-sizing and thus, decreasing pixel sizes to make them invisible. I work with an 8 megapixel Canon and as well a Sony. Both are equally sharp but the former has a quieter image due to its larger sensor. I can print considerably LARGER than 20 by 30 with fantastic results after resizing and some modest sharpening. It is far superior to any 35mm camera film image. Remember, one does not stand two cm from a poster and analyze its micro structure. That is not the point of an image and surely, not that of a poster. There is very little visible difference between a 7 and and 8 megapixel sensor...Remember, its relationship is the square root of the sensor. If there is a good lens and a good steady image and if you judiciously use sharpening and resizing algorythmns such as bicubic ( sharper) than the results will be fine. I recommend whenever possible, that RAW files be the choice if that is possible but if not, the finest JPG file needs to be created to make less visible any artifacts of the compression ( jpeg) process.