Last year during our Texas Wildflower season, one of my projects was to photograph portraits of the wildflowers blooming on our land. I did not want to disturb the flowers, but wanted to isolate them with a black background. Here is what I came up with!
First, the conditions had to be right. The wind had to be absolutely calm and I would only shoot in the early morning or late evening when the light was soft and fading. I took a 30x20 black piece of cardboard. I would drop it in behind the wildflower I wished to photograph, trying to gently pull the other wildflowers around it out of direct contact. Using the tripod and a macro lens, I focused and captured the image using a remote control. Sometimes the exposures would last up to 5 seconds because the light was so low.
It would often take several attempts to get exactly what I wanted. Even the slightest movement took away the sharpness and focus.
After I had an image I was happy with, I'd transport it back into Photoshop. Using adobe bridge, I used the black slider and turned that black background into absolute black while maintaining the brightness and color of the chosen wildflower. I'd also either clone out or crop out any flowers surrounding my subject, leaving a clean black background with my one Texas Wildflower subject.
Here is an example of my Texas Wildflower Portrait project... An Indian Blanket image...