Hello all,

New here. Building my first 4x5 camera, following (mostly) Grepstad's design, with standards based on an old Burke and James design. Completed front and rear frames, plus ground glass holder and spring back, and bought a used Cambo bellows and Fujinon 135mm f/5.6 lens. Bellows turns out to have some pinholes, so I've started thinking about making my own.

Searching forums here and elsewhere, it looks like light-tight material is hard to come by, with the curtains from Thorlo labs being about all that is available. So I decided to experiment with easy-to-find (and not-so-easy-to-find) alternatives.

The not-so-easy-to-find stuff is some aluminized cuben fiber I had lying around (cuben fiber is an ultralight, ultra-tough fabric developed for racing sails that's been widely adopted by the ultralight backpacking community). The easy-to-find stuff is aluminized mylar (polyester) space blanket. Neither is light-tight on its own--both are very dimly translucent. I gave both materials a coat of flat black paint (Krylon Dual Superbond, claimed to stick to plastics), which seems to block all light. After an hour dry time, the paint appears well-bonded to substrates.

Next, I used 3M General Purpose 45 spray glue to bond black cotton broadcloth to the painted sides. Testing by crumpling and creasing and holding against a strong light showed light leaks. I made another pair of samples, this time painting both sides of the substrate, gluing broadcloth to one side and 1.1 oz calendared ripstop nylon to the other. Use of nylon was inspired by Intrepid Camera bellows. This time, the assembly remained light-tight, even after creasing and folding back and forth multiple times.

For both substrates, the thickness of the whole assembly is about 0.015" or 0.4mm. Adding cardstock stiffeners brings the thickness to about 0.03" or 0.8mm. This is a bit thinner than the Cambo bellows, and should be lighter as well.

Next step is to build a complete bellows and test it--I'll post pics here when I do.

My ultimate goal, once I finish the first camera, is build another weighing less than 2 lb (900g) not including lens and lens holder. Monorail, full movements, frames made from 2mm carbon fiber panels, with 20mmx20mm carbon fiber square tube for rail.

Any advice or suggestions is more than welcome--I'm a fairly experienced maker of things, with access to a CNC mill and full shop, and have some experience in 35mm and digital photography, but first experience with LF will be when I finish building a camera and start figuring out how to use it.