Lumen Print Experiments

I recently saw an article on Filmwasters website about a guy selling a little wooden box camera that he calls Lumenbox, and doing Lumen prints. I decided to try my hand at it.

In the short Lumenbox video you can see him doing what at first glance appears impossible: exposing paper negatives to bright sun, then loading them into the little box camera, but not before first wetting the paper in a little container of water. After some time in bright sun, a pretty conventional looking paper negative results, straight out of camera. I did some thinking about this, and then remembered a textbook on photography science that I had around the house, which revealed the answer.

Silver halides have this property, if given sufficient exposure, of auto-development. That is, the halides will turn a darker tone or color, merely from the action of exposure to sun; without the aid of any development chemistry. Of course, the process is almost too insensitive to light to be of any use photographically, unless you're doing lumen prints in a pinhole camera of the sun's course across the sky over weeks or months time.

The little wooden Lumenbox camera has a sufficiently fast lens to capture a sufficient exposure in about 15 minute's exposure to a brightly sunlit scene. I remembered that I had a cardboard box camera with plastic, credit card-sized fresnel magnifier lens, which I used for my initial experiments. Here's the video I made on that project:



Later, I decided I needed a better quality optic, and so salvaged a broken Riteway film holder by replacing its cracked dark slide, and proceeded to employ my Speed Graphic and Fujinon 135/5.6 lens. The image atop this article is from that camera, which I documented in this video:



The key to making this process work is wetting the paper before placing it into the camera. I'm not enough of a scientist to understand what the water does to the emulsion, but the image above was make with a 43 minute exposure in bright sun - accidentally prolonged due to my forgetfulness. I suspect a shorter exposure would have sufficed, since it appears that the highlight density is self-limiting; as that portion of the paper darkens, it limits additional light from affecting further exposure. So even though this was in high-contrast, sunny daylight conditions, the grade 2 paper seems to have produced a very good paper negative image, whose inverted tones can be seen here:



I made reference in the video to the paper perhaps being developer-incorporated, which might explain how the pre-wetting affects a better negative image; but this might be in error, as I've been reminded that few modern paper have developer-incorporated emulsions.

Going forward with this project, I'd like to take the Kodak Ektar 127/4.7 lens out of the camera obscura box and repurpose it for these lumen prints, since it's a bit faster than the Fujinon lens. Second, I have a number of various out-of-date print papers in my darkroom that I'd like to experiment with. Third, if having the emulsion wet is important to the process, would it be advantageous to periodically re-wet the paper in-camera, with perhaps some form of spray system? More experiments are warranted.

Speaking of experiments, in my first video I'd mentioned using a base-pH water solution for the pre-wetting, which did affect a different, slighter more contrasty and dense image. I need to work more with this idea and see where it brings me.

This is a quirky process, a light-sensitive medium that requires no chemical developing agent; yet it's rather impractical for subject matter other than still life and landscapes. As for reproducing the images, it really begs to be a hybrid process, combined with scanning into a digital file, given the paper's continued light sensitivity and hence unknown fragility. This implies that some experiments around fixing these images need to be conducted; but conventional fixer will usually cause these auto-developed images to vanish forever. I've thus far taken to storing these negatives in light-tight sleeves, until I have a permanent solution in place.

What I love about this process is its impracticality, especially in contrast with the state-of-the-art in digital image capture. Whether real "art" can be made using this method is entirely up the practitioner, however.