The highest resolution supported by the Optoma DX328 is 1600 x 1200 (UXGA). That's over six times the resolution of the most common graphics resolution of 640 x 480 (VGA) (which is also supported by this projector). This Optoma data projector also support graphics resolutions of 1024 x 768 (XGA) and 1280 x 1024 (SXGA) and 800 x 600 (SVGA).
This data projector's resolution (1600 x 1200 (UXGA)) is actually the best supported resolution across all projectors of this spec and age.
Across similar types of data projector the worst supported resolution is 640 x 480 (VGA).
There are a number of alternative multimedia projectors that support graphics resolutions of 1024 x 768 (XGA), 1280 x 1024 (SXGA), 1600 x 1200 (UXGA), 640 x 480 (VGA) and 800 x 600 (SVGA) which you might want to also look at including the DX325 (£310.14), or the DS311 both from Optoma which have a better Kagoo Rating™.
If you are looking for a projector with a higher resolution then you might want to also look at the Benq MS521 (800 x 600 (SVGA and higher rated),1600 x 1200 (UXGA and higher rated),640 x 480 (VGA and higher rated) and higher rated).