Quote Originally Posted by CPorter View Post
Been looking at the spread sheet, the 21st or 31st step is shown as being the chemical fog density, but these are defined steps and clearly, at least from my tests, contain density both from exposure and chemical fog.
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It depends entirely on the amount of exposure you give during your test as to whether step 31 on the tablet contributes to exposure or not. Ralph's spreadsheet actually relies on there being no exposure for at least the last step, otherwise it can't work out the base+fog density which is critical for its calculations.