Quote Originally Posted by devb View Post
Could the other variables include environmental factors like the spectral qualities of the light being captured?
Yes, of course, as film spectral sensitivity is not flat. SPD (spectral power distribution) of light that our silver crystalls receive depends on the illumination SPD and on the spectral reflectiveness our subject has, and our filters. So at the end we have light with particular SPD reaching our silver crystals. Is SPD peak hits a valley in the film spectral sensitivity curve then we need longer exposure, with greater LIRF correction (Low intensity reciprocity failure).


I may be like the way exposure correction for a particular color filter depends on the light source, see here different corrections for same filter (for TMX) depending on if daylight or tungsten, page 20 : http://www.kodak.com/global/en/profe...JGWRQHIO3JXWJI


Also a great variation (Alaska -30ºC vs Death Valley +45ºC) of temperature will substantially change LIRF, it is lower with cold, as astronomers saw in 1930s, they were using "dry ice" cold backs.