Inspired by a 1976 video created by The Royal Institution, Krasnow takes “photosynthesis photography” to new levels by building his own camera and creating an original photo on a leaf.
Before getting to that level of complexity, it is worth looking at the much more basic versions of making images on plant leaves, also called “chlorophyll prints.” A popular way to make chlorophyll prints is to expose an existing image onto a leaf, treating the leaf itself like photographic paper.
This distinct photographic printing process relies heavily on a plant’s natural biological processes rather than putting artificial or harmful chemicals onto the leaf. By controlling the pattern in which sunlight falls onto a plant leaf, the areas that receive the most light will perform photosynthesis more rapidly. If the plant has excess energy, it will store some of the energy it does not need in the form of a starch granule. During the development process, the starch is stained dark blue, revealing the patterned light that fell on the leaf during the “printing” process.
Once a leaf has been exposed, it must be developed. The two-step process begins with an eight-minute boiling alcohol bath to remove the chlorophyll from the leaf. Pure ethanol is the recommended option, although it can be challenging to find.
The boiling process heavily dries out the leaf, which makes it crispy. A couple of minutes in water will help rehydrate the leaf before the final step in the development process.
The next step is when the magic happens. With a rehydrated but now very pale leaf, putting it in an iodine bath exposes the starch granules hidden beneath the leaf’s surface. These granules are organized according to whatever a person used to control how sunlight fell on the leaf.
The iodine solution creates a chemical compound with the starch granules, and as Krasnow notes, the risk of overexposure is minimal with this process, so photographers should just keep a leaf in the iodine solution until it does not get any darker.
Once complete, the chlorophyll print can be dried and preserved. These prints can be surprisingly detailed and offer exceptional resolution, as highlighted by artist Almudena Romero in an article on Lomography.
These prints are an enjoyable, relatively straightforward project that is safe for all ages. However, Krasnow wanted to take it further and build a camera that projects an original image onto a leaf rather than relying upon an existing print to control the light that strikes the leaf.
He built a massive lens using a large Fresnel element on the front and a single glass lens on the back. The colossal lens brings in considerable light and creates a large image circle through the back. Krasnow says it is an f/0.5 lens, so it is very bright.
Adjusting the distance between the elements changes the lens’s effective focal length, and he ultimately settled on a lens that is about 100mm. While the homemade lens has some issues with aberrations, it is not problematic for the photosynthesis photography project.
To see more from Ben Krasnow, visit Applied Science on YouTube.
Image credits: Screenshots from Krasnow’s photosynthesis photography video