One of my current research projects is related to hydrogen infrastructure safety. We study how hydrogen flames behave and how large they become if the gas leaks from a storage tank or a pipeline.
Recently, our industrial partners tried to photograph a hydrogen flame and found that it was not easy to capture the details of the flame because the fuel (hydrogen, in this case) burned very cleanly, so there were not many particles in the flame to “mark” it. This challenge is not unique to the scientific experiments, but is common in conventional photography when fire is involved. So here are some notes on photographing flames.
Including fire in a photo can add dramatic impact, because we, as humans, have a deep emotional connection to it. I wrote before about shooting portraits by a bonfire, but when the fire itself is the subject, different considerations and camera settings apply.
How easy it is to see (and therefore, photograph) the flame depends on the fuel. Generally, for artistic photography, we prefer fuels that do not burn cleanly, but instead “volatize” tiny unburnt particles into the flame, which serve as flow tracers and give the flame its color. Precise color of the flame depends on many factors involving fuel-air mixing, but generally, burning wood, paper or natural textiles give a warm, yellow-orange flame color, while gas- and alcohol-based fuels burn with bluish color. As I mentioned earlier, hydrogen flames are nearly invisible (fortunately, they are not common enough to be a popular subject).
Wood fire is quite easy to photograph, because it emits a lot of smoke and unburnt particles. To capture the details of the flame, a dark, uniform background and a fast shutter speed (shorter than 1/250 sec) work best.
Sometimes, it is best to focus on the traces of sparks (e.g. in fireworks), in which case, I usually take long exposures (2 – 10 sec) in bulb (B) mode.
Smoke is an interesting subject too. It usually requires an additional light source to capture the details of a smoke plume.
When fire is an important part of the photo, but there are other elements in the frame, the main challenge is the high dynamic range in the scene that may be beyond what the camera’s sensor can capture. In this case, I expose for the fire, which is usually the brightest element, and add more light to the other subjects using flashes or in post-processing.
