@Diadalos;
Please be considerate of those who are on dial-up connections.
If you insist on "shrinking" your uploads to the maximum 500kb....you will be losing almost all of the folks who are still on dial-up.  I for one will be very reluctant to wait for a 500kb image to load unless the thumb is a real stunner.

For your info, here is a discussion we had a while back regarding image sizes;

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2747600

I routinely compress 36MB TIFF files for upload here...they end up being around 200kb...if they're "mussied" up...it's because of my lack of photographic skills, not compression.....

In youth, we learn....with age, we understand.