After 5-6 years of no darkroom fun (I was on an expat assignment for work and all my equipment was in storage), I have returned and built out a new darkroom in my basement. Been shooting and working darkrooms as a hobby for decades. I have always loved my Beseler 23CII enlarger and love taking care of old equipment (we will lose it all one day if we don't), and to be honest, the equipment has taken care of me.
That all being said, I’m recalibrating an RH Designs Analyser Pro after several years in storage and I’m running into behavior that seems inconsistent with my previous calibration notes.
My setup:
To slow exposure times, I added Tiffen ND filters to the enlarging lens. I verified the ND filters independently with a Sekonic spot meter and they appear accurate (e.g. ND 0.9 giving approximately a 3-stop reduction). However, even after installing the ND 0.9 (3-stop) filter, the RH reading only increased to roughly 5–6 seconds under the same conditions, which seemed implausible.
Yet actual paper tests suggested much longer real-world exposures before reaching D=0.04.
Following the RH calibration procedure, I:
What further confused me was the size of the correction factors required to obtain a usable D=0.04 calibration strip. To get workable test strips, I ultimately had to increase exposure approximately +3 stops for Grades 00–3 and approximately +5 stops for Grades 4–5 relative to the RH’s initial readings. The resulting calibrated exposure times then became extremely long and inconsistent with both my historical notes and my prior experience using this exact enlarger and analyser combination before it went into storage.
At this point I’m trying to determine:
I’d appreciate hearing from anyone with substantial RH Designs calibration experience, particularly with condenser enlargers and Ilford MG filters.
Dowd
That all being said, I’m recalibrating an RH Designs Analyser Pro after several years in storage and I’m running into behavior that seems inconsistent with my previous calibration notes.
My setup:
- Beseler 23C condenser enlarger
- 75W PH140 bulb
- EL-Nikkor 50mm and Rodenstock Apo-Rodagon 80mm enlarging lenses
- Ilford MGRC paper
- Ilford MG filters inserted in the enlarger filter drawer above the condenser/lens path
- Glass negative carrier
- RH Designs Analyser Pro
To slow exposure times, I added Tiffen ND filters to the enlarging lens. I verified the ND filters independently with a Sekonic spot meter and they appear accurate (e.g. ND 0.9 giving approximately a 3-stop reduction). However, even after installing the ND 0.9 (3-stop) filter, the RH reading only increased to roughly 5–6 seconds under the same conditions, which seemed implausible.
Yet actual paper tests suggested much longer real-world exposures before reaching D=0.04.
Following the RH calibration procedure, I:
- raised the enlarger head to maximum height,
- stopped the lens down to f/22,
- took an unfiltered reading,
- then proceeded through the grade calibration strips.
What further confused me was the size of the correction factors required to obtain a usable D=0.04 calibration strip. To get workable test strips, I ultimately had to increase exposure approximately +3 stops for Grades 00–3 and approximately +5 stops for Grades 4–5 relative to the RH’s initial readings. The resulting calibrated exposure times then became extremely long and inconsistent with both my historical notes and my prior experience using this exact enlarger and analyser combination before it went into storage.
At this point I’m trying to determine:
- Whether the RH’s raw pre-calibration exposure readings are expected to differ significantly from actual paper exposure times.
- Whether others using condenser enlargers and MG filters have seen similarly large correction values during calibration.
- Whether practical-height/f8 calibration is preferable to the “max height/f22” method in real-world use.
I’d appreciate hearing from anyone with substantial RH Designs calibration experience, particularly with condenser enlargers and Ilford MG filters.
Dowd
