Slave flash for both A80 and 300D?

[rain-]

I usually don't use flash when taking pictures, but it would be really nice to have a slave flash and actually learn to use it. I have A80 and 300D and I would like to get only one slave flash, is it possible? And since I am asking, what would be a good third lense for the 300D for aquarium photography purposes? I have the EF-S 18-55mm kit lense and Sigma 55-200 1:4-5.6. I suppose I need a macro, but what kind would be the best? Or something else?

Thanks for the help, I am not that good with this hardware thingy :)

[meriadoc]

flash - probably either the 420EX, 550EX or 580EX.

as for lenses, Ed here uses a 100mm 2.8 macro from canon, I use a sigma 105mm macro - both are nice and sharp.

All a matter of what you want to use - just get used to a VERY small depth of field ;)

[rain-]

Thanks :)

*goes to write a shopping list*

[paradise]

Rain, I have the 100mm 2.8 Macro, which I like a whole lot. It's a heavy and big lens, costs around $350-400, but is a great "detail" lens. I also have the 50 mm 1.8 fixed lens, which is an inxpensive yet very effective aquatic lens. It's got a 1.8 Aperature, which lets in a lot of light, even at ISO 100, and is EXTREMELY lightweight, it weighs literally nothing, less than the stock lens. The bokeh is a bit spotty for my taste, and the DOF is really razor thin at 1.8 but it's a great "fish profile" lens, and is fairly quick.

Either one is fine as a choice.

As far as flashes, the 580 is a great flash, but you can also prob. do better by getting a wireless transmitter and a couple of 440s as slaves. That is a great aquatic photography setup.