This section is for performing the film calculations
of Exposure, Reciprocity, Speed Correction and ISO/ASA to/from DIN conversion.
This section uses formulas from “Astrophotography for the Amateur”. See
bibliography for more information. This section based mostly on Michael
Covington’s book “Astrophotography for the Amateur”. Covington
Innovations Note that I have added combo boxes to make entry for some
variables easier. Just select the check box next to variable and then pull down
the desired value.
the Exposure Calculations enter the film ISO/ASA, the lens f ratio f/,
the Brightness Coefficient and the Schwartzschild Exposure Coefficient. Press
“Calculate” to compute the Time and Actual Time of the film. “Clear” to
erase and try again. The
Exposure Coefficient is film dependant and
can range 0.6 to 1.0 for most films. Check with your film supplier/manufacturer.
Typical values are 0.65 for most 400 ISO films, 0.75 to0.8 for Technical Pan
2415 and Panatomic-X and 0.95 to 1.0 for a film that shows little reciprocity
failure (such as spectroscopic or gas-hypersensitized films).
the Reciprocity Calculations enter the time in seconds, p the film
Schwartzschild Exposure Coefficient and the Rated filmISO/ASA. Press
“Calculate” to compute the Actual Time or Actual Speed of the film corrected
for reciprocity. “Clear” to erase and try again.
the Speed Correction enter either the Uncorrected or Corrected ISO/ASA
setting for the selected Filter setting number and it will convert to the other.
Press “Calculate” to compute or “Clear” to erase and try again. Filter
settings are based on Transmissibility Factors and can range 1.0 for clear, 1.2
to 2.0 for light filters, 8-10 solid colors, 16 for dark blue to 20 for dark red
or dark green. See Covington's "Astrophotography for the Amateur" page
83-83 for the color filer table.
the ISO/ASA<>DIN conversion enter either the ISO/ASA or DIN number
and it will convert to the other. Press “Calculate” to compute or
“Clear” to erase and try again.
this site for more information about these film standards. ASA,