A question about picture sharpness

At my previous website I used Jalbum to present my pictures:

http://www.krovoll.net/Kraakvasstind/
this the main page of this "Kraakvasstind" album -- look at the nice and sharp thumbnail pictures!

Each picture is presented in full size like this:

http://www.krovoll.net/Kraakvasstind/slides/P11.htm
this is the full size 1000 x 750 (reduced and enhanced/USM from a 10 mb canon EOS 30d picture).

My new Joomla/ gallery this is presented like this:

http://www.itrollheimen.net/index.php?option=com_gallery2&Itemid=102&g2_itemId=3238&g2_imageViewsIndex=0

My questions are:

a) How can I get such nice and sharp thumbs AND nice and sharp reduced pictures in Gallery?

b) when you click on the picture you get the nice and sharp full size picture,
is there an component/ modul that presents these in a pop-up / full screen mode?
(like Simple Image Graphics)