Top tips: Capture fluorescing flowers
Get a UV flashlight
The Convoy S2+ UV LED flashlight used here has a concentrated UV beam, so keep it away from eyes, even with your safety glasses on. This 365nm torch is mostly used by mineral-lovers seeking out rocks and gems or testing minerals at shows. But it’s also ideal for capturing fluorescence in flower photography.
Attach a ZWB2 filter
This little circle of glass behaves as a longwave bandpass filter, cutting out some of the light spectrum outside the UV range. By doing so we prevent visible light from overpowering the weak UV reflectance in flowers. You can tape it to the front of the torch or unscrew the head and fit it inside.
Set an exposure
The correct exposure will depend on the strength of the torch and the amount of UV reflectance, so it may take some tweaking to get right. As a starting point, set the camera to Manual mode with a shutter speed of 15 secs, aperture f/8 and ISO100 (or some variation of this, like f/11, 30 secs).
Focus then lock
When shooting in low light like this the camera’s autofocus has a tendency to hunt around for the point of focus, so it’s best to turn on a light (or if outside, shine a normal torch light on your subject), then pre-focus on the plant. Once locked on, switch to manual focus to keep it in place.
Start light painting
After starting your long exposure, shine the torch over the flowers. We can concentrate the beam in different areas of the composition to build up the lighting on both the subject and surrounding plants. Take note of which areas fluoresce the strongest and arrange the flowers to include these parts in the frame.
Sculpt with the light
Experiment with the angles of the torch, as a side-on light will help to reveal the texture and detail in the flowers, while plunging other parts into shadow. By shining the light at the front, back and sides of the subject for varying lengths of time you can mimic a two-, three- or four-light setup.