Approximate ISO-EI speed test with in-camera (LF) contacting
1. Shortcut: I’m blanking here – is there a series of formulas to convert a meter reading (for example 1s@f/8, ISO 100) to H in lux-seconds (or millilux-seconds)?
2. A long way (in-camera contacted wedge) which will include flare:
(i) Use long lens and/or avoid wide apertures to eliminate falloff
(ii) Mask lens to substantially eliminate lens/camera flare
(iii) Point camera at white card target (set to infinity focus)
(iv) Meter card at film ISO speed
(v) Give 5 (arbitrary) stops more exposure so that wedge step with D 1.5 corresponds to metered (middle grey) exposure on film
(vi) Develop film, measure densities: If no flare was present and development was correct, exposure from wedge D 2.5 should correspond to film net D 0.1 and exposure from wedge D 1.2 should correspond to film net D 0.9
Obvious problem is flare. Other problems? eg: meter calibration (12%, 18% etc.)?
3. A longer way (no wedge) with no flare (same as roll film methods):
(i) Mask lens to substantially eliminate lens/camera flare
(ii) Point camera at white card target (set to infinity focus)
(iii) Meter card at film ISO speed
(iv) Expose sheet at 3 1/3 stops less exposure than metered
(v) Expose second sheet at 1 stop more than metered
(vi) Develop film, measure densities: If development was correct, film net Ds should be 0.1 and 0.9 respectively
Same meter calibration issues as in test (2)
How bad is all this on a scale of 1-10, 1 being great, 10 being absolute failure?
(My lack of sensitometer is why I continue to contemplate these procedures)