[reeferaddict]

The only dumb question is the one you never ask....

I got two flashes because they work as a master/slave combination so that you can have one off camera to provide lighting from a different angle to cut down on glare and provide fill flash etc. Straight on flash photography throws harsh shadows and highlights that scream "FLASH SHOT". I also got an ST-E2 flash transmitter so I can use both units off camera as slaves wirelessly. Both are about the same except the 430 will only act as a slave and the 580 is more powerful and will act as a master or a slave.

OK... on to IS...

When you are shooting, to eliminate blurry photos due to camera shake the recommended shutter speed is 1/focal length. So if you are shooting a 300 mm lens your shutter speed should be less than 1/300. This has absolutely no bearing on "stopping motion" in your photographs, this is just to eliminate blur due to shaky hands including the most steady of hands. If you have IS you can take the same shot at 1/30 or 1/60 allowing you to use a smaller aperature so you can get a larger depth of field or to be able to get the shot using available light instead of using a flash.

Here's where IS conflicts with moving subjects - To "stop motion" in a photograph you have to use a shutter speed of at least 1/60 or 1/125, even higher if you have a fast moving subject. As you can see, IS will let you shoot at shutter speeds lower than that even with a long lens, but the lower shutter speeds will make anything moving in your frame turn out blurry. I would learn to shoot without IS ... experiment with it on the 17-85 lens and you will quickly learn when to use it and when not to. Having said that, I would definitely go with the 70-200 4L. The lens is PRO quality, excellent build and more dust and weather resistant, as well as having flourite elements and low dispersion glass as all "L" lenses have. All these factors add up to superior contrast, sharp and fast autofocus, and almost a total elimination of flare. I have to warn you though, "L" glass is almost as addictive as reefkeeping!

As for macro, I don't yet have a true Macro lens. I am leaning towards either the EF-S 60 2.8 macro or the one Ruth has the EF 100 2.8, but now I see Sigma has come out with a 70mm 2.8, and I used to have a Tamron 90mm 2.8, a very sharp macro lens indeed! I think I will stick with Canon though as both those lenses are compatible with Canon's ring lights and serious macro work will require a flash so you can shoot at smaller aperatures to have greater depth of field. The shots I put up of the Powder Blue tang were using a 135 2.8 prime with an extension tube. The extension tubes work great with a prime lens to get macro shots. All they do is lengthen the distance between the lens and the film plane to allow for a closer focusing distance. For example the lens I used for those shots normally has a minimum focusing distance of 4 feet or so, slap on an extension tube and I can focus down to 4 inches or so but lose the ability to focus to infinity. As you can imagine, lighting an object only 4 inches from the front of the lens can provide some lighting challenges, especially with a flash head that sits up on a camera's hot shoe so far away from the lens... this is why I have flashes that can be mounted off camera and why I'll eventually get a Macro Ring Light flash unit.

BTW - the built in flash on the 20D will be adequate for probably close to 75% of your flash shots, and you can get cheap slave units to augment that until you can afford a bigger flash...