Not surprisingly, I wanted to find out how good the picture quality would be.  So I carried out the following test.  I selected one of the pictures I had taken and had it blown up to A1 size (about 24 x 36 inches).  As part of the preparation effort before enlargement, I increased the image size from 2,048 x 3,072 pixels to 4,800 x 7,200 pixels, using "bicubic interpolation".  This would enable printing at 200 dots per inch.  Everyone will tell you of course that it is impossible to create more picture information after the fact.  Hence, the resizing should not matter.  I did it anyway, knowing that the print shop would print at 200 dpi.  This way, I controlled how the additionally necessary pixels were created (i.e., the interpolation type used).  Furthermore, I used the "unsharpen" feature, which sharpens hard edges, but leaves the rest of the image unchanged.  Finally, the print shop also increased the image brightness by 10%.

The result was a positive surprise, even to the people in the print shop.  It was a poster size picture with the sharpness of a typical digital photo.  Very impressive.  The quality was considerably better than that of posters created by scanning 8 x 12 inch photos and then printing them at larger size.  The poster was much sharper, showed virtually no grain, and had a great range of colors (hues).  The only weakness was a slight look of artificiality, most likely due to the image size enlargement and interpolation. 

The picture to the left is the one I used for the poster.  Note the fine dark line on the gray building in the background?  It looks like a hair or piece of dirt, doesn't it?  Well, it's not.  Have a look at the image on the right (cut-out) that went to the print shop.  You'll see it is scaffolding.   Depending on your screen, the picture to the right will be roughly 2 to 3 times actual size of the final print.  NOT BAD!

What did I learn from this exercise?

• Good quality posters can be created using the EOS 10D (with a good lens, 100 ASA sensitivity setting, high resolution JPG--not even RAW).
• The poster image quality is superior if the entire process is kept digital.  Take the picture digitally, make any necessary digital modifications, then print digitally.  In my organization we have previously made posters from medium format negatives (6 x 9 cm), but even they cannot compete in sharpness, if the final result is printed using a digital printer, thus requiring a scanning/conversion process in between.
• The EOS 10D images may be "print optimized".  They look good on screen, but look better printed (my subjective impression).
• As usual, always try the extreme--you'll likely be positively surprised.