Thursday, 24 November 2016

Pinhole Camera – 4x5, 60mm – Test Image

After the paint had dried on the inside, I took the camera out for a test.
The 0.3mm pinhole has an effective aperture of f/200 for the 60mm focal length. This gives an exposure of 10s with +1 stop for reciprocity failure compensation.
Which I timed on my phone.
And then used the ‘Massive Dev Chart’ app to help with the development (awesome app, you should get it). I processed the 4x5 sheet film (Shanghai Pan 100, aka ‘GP3’) in Rodinal at 1:49 dilution.
I normally print my negatives, so wasn’t setup to take a scan (photo) of a 4x5 negative. I placed the negative on my tablet computer. This resulted in a bit of a weird image (as you can see the pixels) but was good enough for a test.
With the image inverted in GIMP. The grey area on the left is an inverted white reflection of my ceiling. Good enough for a test. Looks like I needed to add more reciprocity failure compensation.

Sunday, 20 November 2016

Pinhole Camera – 4x5, 90mm (Build Part 2)

Minor update on the 90mm focal length pinhole camera. I sealed the joins with black silicone, then painted the inside with matt black chalk board paint. I made sure to cover the shiny brass bolt in lots of paint so it doesn’t reflect.

Saturday, 19 November 2016

Pinhole Camera – 4x5, 60mm (Build Part 1)

This is the second pin hole camera I started to make, and the first I have finished. The last camera was made out of Oak and used butt joints, this one is made out of Mahogany and uses dove tail joints.
Cutting the tails and pins.
A closer look… these were my first dove tail joints and whilst ok they weren’t as good as I’d hoped.
Test fit. They fit together fine, but not as close as I’d have liked.
I’d previously created a wider board by joining two pieces of stock together. In this case a cut the second piece in half, so I joined a half on either side of the first piece. I did this so I wouldn’t have to drill a hole for the pinhole on the join. I really wanted to see how the wood would look with a finish, so added some bee’s wax.
I glued up two more pieces of stock for the back, this time I didn’t need to worry about the join being in the middle.
I added a border for the film holder to fit into, and also cut a channel for the notch on the film holder to fit into.
I cut a notch out of the side of the camera to let the film holder sit inside the box slightly so that the edge didn’t line up with the light seal. I added a lip all round the inside of the camera for the film holder to sit on.
Test fit of the film holder. Once it fit correctly, I could add the hinges to allow the back to open to accept the film holder.
Hinges added. I used brass ones and made sure to recess them.
The film holder fits in quite snug.
I still need to add some felt to act as a light trap. This will also give some spring for the catches to work with.
Next I drilled a hole for the vertical spirit level.
And same again for the horizontal one.
Next I did the same for the tripod mounts.
And again…
With the tripod mounts and the spirit levels epoxied in, I added the catches.
And drilled the hole for the pin hole to be installed. The pin hole will be glued on the inside, but I need to make sure that the outside won’t vignette as the wood is quite thick here, hence the step cuts.
I added opaque sealant (black silicone) to the seams and a felt light trap. This also adds some pressure to the catches (which I had notched anyway to stop them flying open).
Building the shutter, here you can see the holes for the magnets, and the magnets themselves.
Holes drilled in the camera body ready for the magnets.
I used the same black silicone sealant to glue the pin hole into the camera, then painted the inside of the camera with chalk board paint.
Next was some furniture polish.
All ready to go! Smile