7 Cadobo Cam Lumen Exposures

And learning a lesson from them


sonny rosenberg

4/13/20232 min read

I've been a bit frustrated with the Cadobo Cam that I've been working on. My goal with a lumen camera using black and white photo paper is usually to get what I consider to be interesting colors. I have been able to get decent colors recently, but through more extravagant measures than I'd prefer to take. It took more digital tweaking than I'm comfortable with to get the colors in many of the recent lumen shots. I think this is largely because I just haven't been able to achieve the contrast that I'm accustomed to, and I think I've figured out why.

With Jorge Otero's wonderful Lumenbox, I, over time, figured out that pretty much the longer the exposure, the better (more intense anyway) the colors. I think that over time this conditioned me to by default opt for longer exposures. With the Lumenbox exposures of 10 or 12 hours or even several days were often optimal for what I was trying to achieve.

The Cadobo Cam however is a nuther beast entirely. The box itself is much more vapor tight so that soaking the paper in water as I always did with the Lumenbox often backfires on me. I've learned to only lightly mist the paper for the Cadobo Cam or leave it dry. The lenses are also much different, the Cadobo has a substantially larger Plano-Convex plastic lens than the Lumenbox's Bi-Convex lens as well as a much larger aperture, f/2 for the Cadobo compared to f/4 for the Lumenbox. Taken all together I believe these differences are significant.

Yesterday and today I began to experiment with shorter and shorter exposures. Today was a bright sunny day, so I feel like these are valid comparisons. As it turns out, the shorter exposures had consistently more contrast. See that, I actually learned something! I realize that in the photos that some of the longer exposures have good contrast, but those took quite a bit more tweaking in Lightroom to achieve that contrast.

So here are the results of the past couple days exposures. Unfortunately captioning photos on this site is a serious pain in the arsenal, so I'll just list the exposure times in order from top left to bottom right and provide relevant notes. Unless otherwise stated the photo papers were not dampened and the camera utilized its native f/2 aperture. These were all shot on Arista Edu Grade 3 paper.

Left to Right, Top to Bottom Exposure Times:

  1. 10 hours f/4. 2. 3.5 hours. 3. 3hours, light mist. 4. 2.5 hours. 5. 2 hours. 6. 1.5 hours light mist, paper backwards. 7. 1 hour light mist

I realize that this documentation of my pseudo-scientific experiments can make for some pretty dry reading. Thanks for bearing with me!