Originally posted by Carynn Thanks Sagitta....not sure I understand all you said but I think it gives me "stuff" to think about....I'm a bit of a dunce yet about all this...Today I went to a seminar about DSLR camera's. I learned a lot...and I've bought a "dummies" book on dslr photography to help with the basics...anyway, I'm not taking pictures for a living so probably the f/5.6 will suit me fine and I really should try and save the $'s...thanks for your help, you've been really nice and I appreciate it!![COLOR="Silver"]
Starbursts are basically the flare you get from a shot, most noticeable in either night shots or when directed towards the sun or some other super bright point of light. They tend to be star-shaped, hence 'starbursts'. Due to ~math~, the 'old' 10-20mm will have starbursts with 6 points. The f/3.5 version has an added blade, which gives you 14 points. (Even number blades, you get points equal to the blades, odd blades, you double the number) It tends to be a lot more dramatic, for better or for worse.
The extra f/stops basically means that the f/3.5 can shoot faster (ie, less need for a tripod) in darker environments. If you plan to shoot interiors of rooms and don't want to lug a tripod around, this could be important.
As far as night shooting, again its the same issue - a wider aperture (ie, lower f-stop) means you can get the same results in less time when exposing. Not so important for landscapes (you'd want to stop down in those cases anyway), but handy if you're just wandering around wanting to take shots.
As a quick example, here is a starburst from a 6-bladed lens (I think it was my 18-55 kit lens)
...and here are some from the f/3.5 with the extra blade creating a 14-pointed starburst.