This is an image of Papaver Rhoeas and Campanula—or, to use common names, Poppy and Bellflower—both kinds of flowers from my garden.
I place the flowers on a flourescent light box to create a back lit effect and photographed straight down. There’s very little light coming from the front of these flowers. To increase the transparent effect, I sprayed them with water, brushed the water around for even coverage, and pressed the ensemble gently down with a large piece of 1/2 inch plate glass. I removed the glass before taking the photos used to create this composite image.
My technique with this kind of transparent, high-key image is to bracket exposures, all of them biased to the over-exposed side. In this case, I used my Sigma 50mm macro lens. I set the aperture to f/11 and the ISO to 100. Then I made ten exposures, ranging in shutter speeds from 2 seconds to 1/50 of a second.
I started by processing the lightest and brightest exposure (the 2 second one) in Photoshop. Then I gradually layered in detail from the darker versions, using layers and the Paint Brush Tool in Photoshop.
The resulting composite produced the effect I was looking for: the transulence and brightness of a water color with light apparently shining through the partially transparent flowers.