|Print Version||Last modified: December 16, 2014|
Note: The correction tables below are for films made in Soviet Union. Modern color films have much wider range of use. As for modern black and white films, correction values may differ for each type of film. Consult your film manufacturer, make test shots by yourself or use exposure bracketing.
|Exposure correction for FOTO 32-250 (silver-based B&W) films for outdoor shooting, depending on lighting type|
|Electric Light||Bright Sun||Clouds||Clouded Sun or Evening|
|Exposure correction depending on shutter speed
(Compensation of Schwarzschild effect)
|Shutter speed according to the meter||Correction values|
|FOTO (silver-based B&W) films, for ГОСТ/ASA/ISO||Color Negative||Color Slide|
|1/8, 1/4, 1/2||+1/3||+1/3||+1/3||+1/3||0||X|
0 - no correction required.
X - use of this type of film is not recommended with the given shutter speed.
This table has been taken from Robert Kosara's homepage: http://www.kosara.net/photo/pinhole.html.
As mentioned above, pinhole cameras require long exposure times. Starting from about one second, the exposure has to be corrected to account for the reciprocity failure or Schwarzschild effect. The usual way is to open the aperture, but this is not possible for pinhole cameras. So the time has to be corrected, which means that another correction has to be made (because the longer time would need a different compensation ...). The following table gives the corrected numbers for most black and white films (specifically, the Agfa Pan 100 (APX 100)). To calculate these numbers, the following formula can be used (thanks to Dieter Lefeling for that):
tc = 0.1*(10*tm)^(1/(1 - lg 2))
(where tc is the corrected time, tm the measured time, and lg the base 10 logarithm).
Note: The formula can be rewritten as:
tc = 0.1 * (10 * tm) ^ 1.430676558073393
|Measured Time||Corrected Time||Measured Time||Corrected Time|
© Sergey A. Galin, 2005 · sageshome.net