Good day,
I'm on vacation for the next few weeks and I can finally finish a few projects. Normally I'm a big fan of the trail and error mentality, but unfortunately this experiment takes too long for that, so I'm asking you for insights that can solve possible problems. An idea I've had for a while and is now quite advanced, is a solargraphy camera that doesn't use a pinhole, but a "real" lens. So instead of a circular pinhole camera in a can I want to make a box camera with a ultra wide-angle lens and ND filters in order to achieve the correct exposure. I now have a lens, ND filters and a photographic medium in the right format.
The idea:
I have two Minolta 195mm F6.5 photocopier lenses that I can reduce to F45 with an internal waterhouse stop. These lenses fill a 30x40cm negative at >F22. On this I can place two 10-stop ND filters of 58mm on the back of the lens (to prevent reflections and possible water damage). I've confirmed that they only minimally vignette by just inserting the housing of the filters, this only minimally reduces the image circle. I was able to get the two actual filters in one housing, this saves an extra ring, and therefore vignetting. It's impossible to test what this does for the image quality in a short time because no visible light comes through a 20 stop ND filter, but let's hope for the best. Because I don't want to leave a real camera outside for half a year, I'm going to build a box camera and paint it a few extra times. The lens has no openings on the shaft and only allows moisture to enter through the filter thread that the glass is attached to. That way I can put some silicone sealant over this to prevent moisture problems. I can also load RC paper into the darkroom once, so there are no problematic openings in the housing. And just to be sure, I can stick Silica bags in the part where no light passes (against the front panel), I already have these.
Possible problems:
Reciprocity:
The longest exposures I've done on Illford MGRC are around 2 hours and I had no visible problem with reciprocity. Well, this is a completely different order of magnitude in exposure time.
Using two 10 Stops filters. I have no idea if something like this is still useful, although apparently there is a 24-stop filter that works with digital cameras. Fortunately, I'm not too afraid of the color shift, because I use black and white paper.
Vibrations:
To prevent this, I'm going to anchor one camera to the corner of my brick shed at home, and the other to four sturdy posts at a friend's estate.
Exposure:
I calculated the exposure based on 13EV on average for 12 hours of light per day (in the Netherlands). This gives me 20 stops ND at F45 for 192 full days of 24 hours, so just over half a year. But from experience I have noticed that a stop more or less is not an immediate problem with this paper, so I do have the necessary leeway.
Do you see any problems that I didn't foresee? or do you know of anyone who has tried something like this before? I can't find anything except the regular solargraphy cameras.
Thanks for reading, and if you have anything to add please let me know, otherwise hopefully you'll see the results here shortly after the longest day of the year. I try to keep you informed.
Bookmarks