Passion flowers (like Orchids) are a world unto themselves with approximately 500 different species and about as many hybrids. Characterized by a ring of coronal filaments (straight, curvy, spiky, or anything in-between), they appear, to me at least, like flowers from another planet.
When encountering my first Passion flower at a local nursery about 10 years ago, I was impressed enough to return home, get my camera, tripod, etc., go back, and attempt to do it justice. Subsequently I joined the Passiflora Society International, attended one of their annual meetings in Florida, photographed a bunch of different species, and managed to alienate the society president who “never in (his) wildest imagination did (he) guess (I) photographed dead flowers” upon discovering I was working with cut blooms (after he had earlier given me permission).
Whether indoors or out-in-the-field, what is involved here is basically Table-Top Photography. So if you have an actual table top, great; otherwise, the name of the game is Improvise. Any solid surface will do — boxes, stools, apple crates, etc. Believe it or not, at home I often use a garbage can (see “Rings & Things”) that is easy to position with regards to the light.
Procure about one square yard of the blackest fabric you can find; black velveteen, acquired from a fabric store is what I use. If you prefer a textured background, then I suggest acquiring a large piece of “aquarium coral,” about two to three times the size of your largest subject and spray-paint it with quick-drying flat black enamel.
Be creative: smaller blooms on a Lotus seed-pod, or how about a nice piece of bark? One of my backgrounds was made by gluing tiny pine cones next to each other on a piece of cardboard and then spray-painting them black. Any portable textured surface is fair game. Also useful to include among your accessories is black masking tape, good hand-eye coordination, an awareness of light, a sense of composition, and patience.
I used to use a regular 35 mm SLR camera, but now for the last several years have been utilizing the Canon PowerShot G-9 / 11 / and 12 digital cameras. A tripod certainly is useful for deliberate composition, although no longer so important for stability because of today’s excellent internal stabilization. Stop down for maximum depth-of-field and focus about one-third of the way in from the front edge. All these were done with natural light and without filters. Don’t be afraid to bracket your exposures. Another useful accessory is a free-standing hobbyist’s vise that is small, portable, and adjustable. The bloom won’t be resting on anything, but they are ideal for positioning your subjects to show details in the best light possible.
That most dramatic effect of back-lighting is achieved by shooting towards the light, rather than into it (unless you want lens flare) early in the morning or late in the afternoon. If your subject is sufficiently translucent, it will take on a glowing quality and will stand out, especially against a carefully chosen dark background. Cloudy days often result in better color saturation and if the full sun is too harsh, try diffusing it with wax paper, a plastic bag, cheese-cloth, etc.
While my subjects here are Passiflora, I suspect the above can be applied to many other types of flowers.