I shoot with a Canon 40D and a Sigma ef 500 DG Super flash, mainly using a 50mm f1.4 lens, using the center focus point exclusively. Recently I've started shooting in dance clubs and concert events (venues where light is at a premium). http://photo.onsendesigns.com/ The problem I'm having is shooting at really low light conditions, while using the AF assist light to aid focusing results in many missed shots. (The AF assist light is the red light patters the flash puts out, not bursts of the light from the flash itself, just so everyone is clear on what I'm referring to) What happens when the AF assist light kicks in that focusing takes up to a second or two (the red AF assist light/pattern flashes a few times, and with each flash, the focusing gets adjusted a little more). This delay (of even a second) is very annoying and results in many lost moments since the shutter didn't get triggered at the moment I pushed the button, since person photographed is dancing (moving) or artist is moving/dancing/singing. As I have never owned a canon flash (430 or 580) and I don't know if the AF assist red light also flashes or if it's a continuous light on the canon flash?. This may be just a Sigma flash thing? I have tried not using the flash AF assist, and let the camera do the AF in ambient light, but even though the camera's AF indicator light indicates an in-focus image, the final image is less then sharp (when viewed on a computer). When the flash AF assist light is used, images are in perfect focus, which leads me to believe that due to the low light, and low contrast of the images, combined with the low DOF of the 50mm lens wide open at f1.4 (where even a small error in focusing makes a big difference in image sharpness), the AF accuracy is lower. What are my options to improve the focusing time, so the delay is reduces in low light conditions?