I've noticed that the bloom effects on one computer with completely identical settings (in RS) are more pronounced than on the other and cannot be seen through. In some instances, they're slightly ridiculous, such as fish bowls glowing brightly and appearing solid white when dropped (as opposed to minimal glow and natural transparency, on the first).

How can I change these settings?

Do the goblin priests with bloom on... Your screen will just stay completely white. You can still see your interfaces to disable it though...

 

I've not heard of a way to change them. >.<

There is no way to change it currently. It just has an on / off option.

By the sounds of it it's a computer issue (opposed to the jagex end known issue Stev referenced, where some areas are blown out with bloom and being fixed bit by bit), along the lines of an older/less powerful graphics card that can't deal with doing bloom properly so it's fudging up the opacity.

 

So essentially the advice would be play around with your actual graphics card settings on the problem computer see if you can find anything that helps, if not just turn bloom off on that computer.