[ken666]

20D-8mega pixels 放相可放到幾大仲系sharp,想放16x20"吾知夠吾夠像素.

[man1492]

300dpi ~12R

[tam_dominic]

Assuming you look at 5" x 7" at 12 " distance, you'll look at 16" x 20" at 3 feet distance.

If you need 300 dpi for 4" x 6" then
you may need 200 dpi ) for 16" x 20" (in practice it may be interpollated to 300dpi before print)

You may reference the wall size advertisemnet photo and see how many dpi it is.

Happy shooting !