Very useful discussion on these meters!
My main contribution is to underscore that the weakness with this meter is that the prism inside will jump out of place and stay out of place if you drop the meter. Usually just replacing it in its socket inside fixes the problem. I've bought several Soligors that were "not working" on eBay for <$20 when this is all that was wrong. In one case only the prism cut into the wiring inside the moving coil meter itself which made it unrepairable. The other parts could of course be recycled if needed.
Always use the handstrap or the holster that Zone VI used to sell. If dropped and the prism is displaced separate the plastic shell sides and gently replace it in the molded socket with the spring holder in place. There is a screw in the battery compartment, I think one cross screw, and you have to loosen the knurled lock nut that the eyepiece screws in and out of to focus. Just turn this knurled nut CCW using padded pliers until it's a little loose and it will release it's clamp action on the two halves of the shell.
These are great meters that I've used for decades. They're a little bulky but other than that just fine. I have both the analog and the digital meter versions and I use them interchangeably. Essential for zone system work. Just do the film speed and development time tests as Picker taught and you'll be fine.
I can see no significant difference with Fred Pickers touted correction. It's a filter in a little cover that fits over the sensor. Zone VI also glued in an O-ring believe it or not inside the lens opening inside the meter obviously for some added light baffling. They may also have painted in a little bit of anti-reflective black paint.
I found I could.increase the linearity of my meter by increasing it's sensitivity one stop which meant I just had to double my ASA to compensate. So I'm shooting 100 ASA film with the meter set at 200 ASA and I get very acceptable linearity down into the low values.
Extreme precision in metering in the field is not necessary IMO. I say it's not even possible with moment to moment fluctuations between metering and exposure. I've found the Soligor to be more than up to the task.
I do routinely check negative densities in sky and shadow to get early warning of weakening chemicals or variations in film speed. I check my field log to see what the sky and shadow placements were by zone and just screen them in a couple minutes as I process film. This validates the entire process. Essential with a new batch of chemicals or a fresh box of film. I put a washed, still wet negative in a mylar 4 X 5 holder and read the density with densitometer. (Plenty of these on eBay with the demise of commercial film usage.)
