How do I set the resolution for images in PopUp?

Hi

I am using the PopUp plugin which has some really great functionality - but when it comes to inserting images it is lacking. I created an image in Photoshop at 1o00px x 200px at 300dpi. I saved for web at 500px x 100px which is the size I want it to appear on screen.

When I upload to the media directory it looks fine. When I add media in PopUP it defaults to 300px x 60px. and the resolution is poor. When I resize it in the html to 500px x 100px it looks simply horrible.

I have even tried typing in the html manually, but the quality is still poor - I don't understand because it is calling on an image in the media library that is OK.

If you go to http://www.wagercentre.com and wait 10 seconds, you will see what I mean.

How do I get crisp images in PopUp?

Regards, Paul