I have been using my KM Maxxum 5D for about a year and a quarter, but just recently started getting stuff for it. I originally got it because my previous point-and-shoots had horrible low-light performance (even bright indoor shots didn't come out well) and I wanted something with a bigger CCD to deal with that.

However, I am now getting into more advanced photography and am starting to outgrow what came in the one-lens kit. I recently bought a Sigma EF-500 DG Super flash, which I have received, and a Minolta 80-210mm f/4 "beercan" lens, which I have not, but should be getting in about a week.

Shooting with my Sigma flash yesterday in lower light, I noticed that the camera was having trouble metering properly. In one indoor portrait shot I managed to overcome the metering problems by setting a +1 eV flash exposure compensation on the body. However, that didn't do the trick when I was taking pictures at a very-low-light musical performance that evening. There, direct flash worked fine (but was ugly), but bounce flash was way too dark at 1/60th of a second. I needed to reduce the shutter speed to between 1/40th and 1/15th of a second, depending on the angle. I also needed to bump the ISO up to 1600 or 3200, which obviously caused some noise. I was using the flash on full power in the default automatic metering mode. Is there something I need to be doing differently?

I think that part of the problem was the 18-70mm kit lens, which at 28mm has a minimum f-stop of f/5. I think I would be better served by a constant f/2.8 lens of around the same focal length -- 17-28 mm minimum, 70-80mm max. Does anyone have suggestions on what lens to get? I want to spend as little as possible, but don't want to go out and buy something that I'll be unhappy with just to save a few bucks. I have been looking at the Sigma 24-70mm f/2.8 but am not sure how well people like that.

Cliff's Notes:

-- Have been using my 5D for over a year and finally starting to buy stuff for it
-- Got a Sigma flash and a "beercan" lens
-- Sigma EF-500 DG Super flash -- having trouble getting bright enough shots with bounce flash at 1/60th of a second
-- Recommendations for a good f/2.8, equivalent focal length replacement for the 18-70mm kit lens?