Last Sunday was Worldwide Pinhole photography Day, so I decided to make a pinhole camera and play around with some exhausted Ilford Ilfospeed x.44M B&W Photographic paper as source material for some paper negatives. The camera I build out of a Chinese Tea Tin lined with black gaffer tape and trilled a hole in it for the pinhole using a set of ultra fine drill bits for the Dremel. Camera Specs: 0.4/75mm f/187.5. Single shot, Paper Negative: 55 x 127mm (diagonal 138.4mm) mounted in a curved plane. Angle of view is 85.4°
Here’s some Pinhole math:
1. 75mm / 0.4mm = 187.5 i.e. f/187.5
2. 187.5 / 16 = 11.71875 i.e. 11.7 x exposure at f/16
3. Reciprocity Failure (per Beal, p164): <1 sec none; 1-15 s = x 1.5; 15-30 s = x 3; 30-60 s = x 4; 1 m-30 m = x 6 4: The Ilford Ilfospeed x.44M series of papers seem to be nominally rated at around ISO 400. The Sunny 16 Exposure is apparently 1/4 sec. Now, we know that at f/16 for ISO 400 that gives us a target Speed of 1/400th sec. normally if we keep the speed, then we drop down in the following series: f/16 - Bright Sun, Hard Shadows f/11 - Clear Sky, soft shadows f/8 - Partly Cloudy, Open Shade f/5.6 - Overcast f/4 - Dark Clouds, Rain f/2.8 - Dawn/Dusk f/1.2 - Street Lights, Well lit night. However, if we keep f/16, as the 'exposure' setting, then we need to change the Shutter Speed. This becomes, (based on the Minolta SRT101) 1/500 - Bright Sun, Hard Shadows 1/250 - Clear Sky, soft shadows 1/125 - Partly Cloudy, Open Shade 1/60 - Overcast 1/30 - Dark Clouds, Rain 1/15 - Dawn/Dusk 1/8 - Street Lights, Well lit night. Given these speed ranges we can then translate to Pinhole Exposure Times, thus. 1/4 - Bright Sun, Hard Shadows that is 1/500 x 125. 1/2 - Clear Sky, soft shadows 1 - Partly Cloudy, Open Shade 2 - Overcast 4 - Dark Clouds, Rain 8 - Dawn/Dusk 16 - Street Lights, Well lit night. Next, we need to consider Reciprocity Failure for long exposures. From point 3 above the table now looks like this: 1/4 - Bright Sun, Hard Shadows 1/2 - Clear Sky, soft shadows 1.5 - Partly Cloudy, Open Shade 3 - Overcast 6 - Dark Clouds, Rain 12 - Dawn/Dusk 48 - Street Lights, Well lit night. and now we have a working guideline for exposing our paper negatives. Because this particular film stock is very old, it may be fogged, it may be discolored, and it may be less sensitive to light, so times will need to be adjusted accordingly. Interestingly though, these are relatively quick speeds. Using a tape shutter means that there is very real risk of camera shake when applying and removing the shutter, and the higher speeds can't be obtained with a tape shutter, at least not with the gaffer tape that I'm using. To give an example, if you take a normal sports stop watch and hit the stop/start button with your same finger as quickly as you can, you might be able to clock in at around 0.7 of a sec. Many clock in at double that. If you apply the same logic to opening and closing your middle finger and thumb, wide, on the same hand, as fast as you can, you might just be able to clock in at 1/4 of a second. Now do that with your pinhole camera without shaking it... So, images? Yes, I have one. It's my first successful image from this camera after much trial and error. The negative was processed in 1.5% Rodinol Developer solution, stopped with running water, then (not really) fixed in concentrated salt solution before being dried and scanned on an HP Scanjet 3110 flat bed scanner. The negative was inverted to a positive in Photoshop and then trimmed, dodged and burned using Lightroom. The original is still a paper negative which I might try contact printing into a paper positive at some later date when I have some propper fixer to use for finishing off the prints.
For today, that’s what’s in my
Line of Sight.