flash setting and camera settings

I'm using a sunpak 5000af with my 20d and it really isnt a good pair because the flash doesnt work properly with it. I'm not sure I really understand how they are suppose to work together. Before I get a new flash, please tell me which is the best to get for the 20D? where do you start with getting the settings right? Do you set the camera differently because you are using a external flash? What kind of setting do you suggest for some extreme different situations? Like your kids school dance in a dark room? Or, outside on a cloudy day? what method do you use to to get the best pics in these situations. assuming that you dont have lots of time to fiddle with things? Is it a good rule of thumb to work in aperture priority? will the 580ex make the proper adjustments? As you can tell, I'm looking for easy to understand terms from the well informed... Thanks again!!

Your Sunpak flash will only work in Manual Mode on a 20D. If you are skilled at Manual Flash, it will work fine. If you want to take advantage of ETTLII, Canon's advanced flash system, you need an ETTL/ETTLII compatible flash like one of Canon's EX Series flashes.
There is alot on this in the EOS Flash Sticky.
Scott

You need to use the old film trick of matching your flast output to distance. Most manual flashes have a guide listing fstop and distance on them. If yours doesn't you will need to make one using a meter. There is a really good article at shootsmarter.com that covers this basic concept.

I kind of figured that manual mode was the only mode that was functioning properly. Let me ask you guys this? Say I have my camera in manual mode and I am 10 feet away from my subject. would I start by setting the correct flash distance with the F-stop dial on the flash. I noticed that when I change the F-stop on the flash it shows me the distance of coverage. After I set the flash distance would I then be correct to assume that the cameras F-stop should be set as the same as the flash? this is where I'm very confused. Should the F-stops match up? Also, if you are using bounce flash off the ceiling should you up the power of the flash?

You decide on the f stop based on distance to the subject and DOF you want. The you check the flash guide. You will have to adjust your distance and f stop to suit your needs. So basically you play with the f stop and distance till you get what works for you.
The f stop on the lens/camera must match the f stop for the distance on the flash. Usually there is a choice of two f stops because of overlapping ranges. If you are in tight quarters, you can't play with distance so you adjust the f stop. If you are far away, you need to open the aperture. As to Bounce Flash, you need to add the distance to the reflective surface and from the reflective surface to the subject. You also have to take into account the reflectivity of the surface and the dispersal of the light. You take a test shot and adjust the f stop or your distance based on the histogram.
Scott

http://www.shortcourse​s.com …enumbers/guiden​umbers.htm
http://www.photographi​c.com …echniques/132/i​ndex2.html
http://bobatkins.com …raphy/eosfaq/fl​ashfaq.htm
http://homepages.ihug.​com.au/~parsog/Guy/fla​shnotes.html