I’ve recently liked to shoot with Welta Weltax folding camera which is manual in every possible way. It does not have a film advancing level nor a range finder. Everything is screwed and set by hand. But it takes 6×6 photos on a 120 roll film and it fits into my jacket pocket. It has amazing photo quality and it looks really nice. Last Sunday (30/365) I took it with me when we went to see the building site of our future home. The apartment building will be built during this year but at the moment there’s nothing much more than piles of sand and machines.
Development notes: Kodak Tri-X 400 was exposed based on Sunny-16 rule, although I think I over exposed the roll. Luckily it was easy to fix during scanning & processing. The film was developed in Kodak HC-110 B in 20°C. Development time was 7:30. The tank was agitated for 30 seconds in the beginning and then 5 seconds every 30 seconds. Fixed and washed.
Film scanned as positive and processed in Photoshop (invert, desaturate, curves). It’s my (new) favorite way of processing black and white film in medium format.
I’ve never really learnt to like Kodak Tri-X but I have to say this roll of film looks pretty good. It was the first time I developed Tri-X with HC-110 and they seem to work really well together. This was my last Tri-X roll though.
Development notes: Kodak Tri-X 400 was shot at ISO 1600 which required a two stop push in processing. Kodak HC-110 (B, 1+31) used as a developer in 20 degrees. Development time 16 minutes, agitated every 30 seconds. Fixed and washed.
Film is a funny medium. Depending on the film, it loses sensitivity when the exposure time is long enough (usually after 1-2 seconds). This is called (low intensity) reciprocity failure (you’ll find science and math behind the link). Basically all you need to know is that you have to compensate the reciprocity failure by extending the metered exposure time if you want to get properly exposed frames. Each film has its own characteristics so the needed compensation is different for each film. Fuji Acros 100 film is one of the only films that have very small reciprocity failure and you can use exposure times up to 20-30 seconds without compensating.
Noon Pinhole camera, Kodak T-Max 100, f/207, 4-5 seconds
Here you can find a small reciprocity correction table for some of the popular black and white films. For example, if you meter that the correct exposure time is 30 seconds, with Ilford HP5+ you have to expose for 54 seconds to get good exposure, and with Kodak Tri-X 400 for 78 seconds (1:18). Google is usually your best friend when trying to finding out the film’s reciprocity failure if manufacturers’ data sheets fail to help.
I’m planning to take a few long exposure photos this weekend. At the moment I’m thinking of taking them with Yashicaflex with cable release. The pinhole camera is another option. I’ll probably use Kodak T-Max 100, Fuji Reala 100 and / or Rollei Pan 25 as the film. The latter would enable really long exposure times. Rollei Pan 25 is said to be very similar to Agfa APX 25 so APX 25′s reciprocity failure compensation could be used. Here’s a screenshot from APX 25′s data sheet.
By the way, digital camera sensors do not have a reciprocity failure.
If you are photographing with a pinhole camera which has an aperture value that is out of your light meter’s scale, you have to calculate the exposure time based on the light meter and then add time for the reciprocity failure. A simple formula for calculating the exposure time (ignoring reciprocity failure) for a pinhole camera is ( f / R )^2 x Tm = Tc where f is the camera’s aperture value, R is the light meter’s aperture value, Tm is the exposure time in seconds given by the light meter, and Tc is the corrected exposure time in seconds.
For example, my Noon Pinhole camera has an aperture value of f/207. My light meter goes up to f/64. If I measure 1/2 second at f/64, the correct (but not compensated) exposure time for the pinhole camera is (207/64)^2 x 0.5 = 5.25. If I was using Kodak T-Max 100 film, the compensated exposure time would be around 6 seconds. With Fuji Acros 100 I could use exposure time of 5.25 seconds because Acros 100 does not require compensation below 20 seconds.