It is NOT used to determine exposure time. It is used to set the f-stop of the lens at a specific number of seconds. The exposure time is constant, the f-stop is what changes.
As for the adjustment pots, you should email roger and get a copy of the instruction manual.
This is what I think it is from memory. But realize that the last time I read the instructions for this device was over 30 years ago, so I claim no accuracy to the following.
- To calibrate, you MUST turn off ALL the lights in the darkroom, including the safelights. The only light is the enlarger.
- The slide switch for 1 and 2 are probably for either of 2 program settings #1 or #2, each is independent of the other.
- I think the * is to calibrate to the black dot on the right of the meter for max brightness (no negative in the enlarger) at a particular enlarger light setting (combination of height of the head above the baseboard and the f-stop the lens is set to).
- I think the delta symbol is to calibrate for a max density. If I remember correctly, you stack 6 pieces of 1 stop ND filter pieces over the sensor. Thus done, from the dot to the 0 on the dial is 6 stops of density. What I do not remember is the exact number of filter to stack, might be 5, 6 or 7. The max number should cover the contrast range for paper grade 0. If you don't have the ND filters, you can order a small sheet of 1 stop ND filter gel from B&H or Adorama.
- Then you remove the stack of filters, and one at a time; put a piece of ND filter over the sensor and mark the scale, then repeat till you have all 6 pieces on the sensor. The meter scale now shows a scale of 6 stops, and you can see where each stop of density is on the scale. So you can determine the density/contrast range of a negative.
To use it, to determine density range for paper grade
- you put the sensor under the clear part of the image.
- dial the f-stop on the lens so the meter aligns to the black dot
- put the sensor under the DARKEST part of the negative
- The meter will show you the density range of the negative in f-stops, which you can then match to the appropriate paper grade.
Caution, some negatives do not go from white to black. When printed they may go from white to gray or gray to black. In other words the negative does not have the full tonal range, because the actual image does not go from white to black. Then you have to use your head to determine what the proper paper is for that image.
To use it set exposure
1- First you need to make a good print, ideally on grade 2 paper. There is no way around that.
2- Then you set the meter to read a particular point of density on the film. When I do it, I meter the clearest spot (where the print will be BLACK).
3- Then you note the meter setting for that; it could be any place on the meter. As long as you are consistent in where it is. In fact you could use that light level to do the calibration above.
4- You have now calibrated the combination of enlarger+paper.
When you put a new negative in the enlarger, you put the sensor under a clear part of the negative and close/open the lens till the meter reading is the same as above in #3. If everything works as it should, you should be close to a good print. You will still have to fine tune the exposure or contrast to be what your eye wants.
If you change to a different paper or grade of paper, you still do the above, but you have to experiment to determine what the appropriate exposure TIME should be for that paper.
Example grade 2 might be 10 seconds, grade 3 might be 14 seconds, grade 4 might be 20 seconds.
As with calibration, when you use it, you MUST turn off ALL the lights in the darkroom, including the safelights. The only light that is on is the enlarger itself.
That is a very cool device, that I would not mind having. But with the cheap price of used color analysers, those are an easier to find option.
