I set up my soft box with a white background first then changing to a black background, I wanted to see how the same object looked with different backgrounds, how would it change the perception of the object.
I decided to keep it simple... a flower. After various attempts at clamping, wedging and leaning the flower I found the best method was to put the stem of the flower into the end of a straw, that way it was more secure and didn't wilt.
Using my Canon 5D MKII, a Sigma 50mm f2.8 DG EX Macro lens and a Canon 580EXII speedlite all mounted on a tripod, Tethered to my IMac and using the Canon software I was able to view the whole proceedings from the comfort of my chair.
Using the camera on a manual setting gave me complete control over all aspect, so I first set my ISO to 100 to ensure low noise and best quality, as I haven't got a light meter I was relying on the in camera metering and review of the picture, checking the histogram to ensure a good exposure. If I was using studio flash I would have set the shutter speed first (good practice) as told by Mr Steve!, However as I was not using Studio flash but my speedlite I wasn't bound by shutter speeds and as I was using a macro lens I wanted maximum depth of field, my Sigma lens is capable of f45 so I set it to that. I knew that this would greatly decrease the amount of light coming in through the lens due to the extremely small aperture I increased the flash output to +3 stops, I initially tried a few shots on a shutter speed 1/200 second, This was fine for the white background shots but this was coming out a bit under exposed on the black backgrounds, again as discussed earlier in the day in the studio, there was probably more stray light bouncing around on the white background, I opened up the aperture to f36 on the black background which looked all ok on the histogram.
All pictures were opened in camera RAW, editing for white balance, an increase in contrast and saturation for black backgrounds and a reduction in Clarity for the white background giving it a more pastel soft feel. Opened in photoshop adjusted with levels to further whiten the whites and darken the blacks. finally creating a new background layer and copying all three selected flower photos on the the new layer, resizing and saving.
Here's the finished results two panels photographs ready for the club competition: