Anyone know how to Calibrate Gossen Luna Pro?

[phototone]

I have a couple of Gossen Luna Pro lightmeters, both work, I use the Wein Air Cells in them to get the correct voltage. (These are original Luna pro, not "F" or "SBC")

However, they are off in exposure. In full daylight, one is off by 1 stop, giving me a reading of (for instance) 1/500 @ f22, for ISO 400 film, when it should give me a reading of near 1/500 @ f16.

I have found lots of sites on Gossen meters, but haven't found one that tells you how to adjust them. (other than the zero adjust, which is obvious).

I figured you guys might know. Of course I want to use these meters, with my classic RFDR cameras.

It seems silly to send these meters off for repair, when all is needed is a little calibration tweaking.

Gene McCluney (Phototone)

 

[kiev4a]

IMHO wein cells are crap. I had a Luna Pro and found an adapter for 20 bucks that allows you to use silver cells. The Weins don't last very long and after you have purchased a couple you could have bought a silver adapter. Sorry, can't remember who made the adapter. I eventually sold the meter and got a later Luna Pro that uses a 9-volt battery.

 

[Nikon Bob]

Gene

Have you tried here for a manual http://www.gossen-photo.de/english/foto_sammler.html. You might have to check a few models out because the European names may not be the same as the North American names. You can contact them directly also and they have been very helpful to me in the past. Lots of luck.

Bob

 

[jlw]

If it were just as simple as twiddling a screw, then Kyoritsu wouldn't be able to sell calibrated light sources for such big bucks. Analog meters are by nature non-linear, so you have to go back and forth adjusting the different parts of the response curve against a known standard to get consistent readings throughout the range.

I'd suggest contacting Quality Light Metric ((323) 467-2265?) and at least getting an estimate for calibration only before dinking with them.

 

[Max]

The luna Pro responds to the voltage, if you can put two batteries that add up to 2.7 volts it will read ok. Ordinary Znairs don't last that much, may be a couple of months. But I found a somehow ridiculous solution. I used Panasonic Znairs and when depleted, they flatted at 1.2 volts. So i tried one depleted ZnAir with one ordinary silver battery, and got something very close to 2.7, and the metter was higly accurate with this combo. It lasted for two years. Now I'm using another depleted ZnAir with another silver one. What I do is carry around in a filter box several batteries in different levels of use, and when you get a combo that adds up to 2.7 volts the battery check measures right on and the mettering is perfect at all light levels. The Luna pro should be zeroed using the screw in the back to work right. If you tweak this screw to get a good battery check reading with a voltage different than 2.7, the readings on the upoper zone of the scales will get completely out of whack, there's no calibration method available without making modification to the electronics.
The meter is big, but beautifully built and extremely accurate even in very low light levels. if you get it to work you'll love it.
On second though, if your metter is zeroed, the voltage of the batts adds up to 2.7volts (top of the red battery check mark) but it's still off, your meter cell might be loosing it's sensitivity, and I think there's no fix for that, except replacing it, which I guess should require another meter for parts.

 

[peter_n]

Bob thanks for the Gossen manual link! 🙂

 

[LCL]

You need Mercury batteries

You need Mercury batteries

Lunar Sixes were designed for Mercury batteries, as indeed were almost all lightmeters and built-in lightmeters of their era. Mercury batteries are unique in that they give a constant voltage right though their life. All other batteries steadily lose voltage as they discharge. This special feature of Mercury batteries meant that the circuitry in light meters could be very simple.

Such batteries are illegal and are no longer manufactured because Mercury is highly toxic, especially in the form that batteries come in.

They also have a very long shelf life, and you may be able to source some old ones. If you do, please, please, please don't throw away used ones. Keep the old ones in an airtight jar labelled "Mercury - poisonous fumes" and wait for a legitimate way to dispose of them.

LCL

 

[Doug]

My Luna Pro F uses a 9v "transistor" battery, the common brick-shaped one. I got it used on eBay, so was not sure it was accurate. Just as a precaution before relying on it, I took it to my local repair guy for a checkup. He fixed some internal wiring and calibrated it. Not a big deal, apparently, and he said it was now right on, and I could use it as an accuracy check for my other meters! So I'd suggest you do the same... 🙂