Gossen Lunasix 3 (Luna Pro?)

While I have no doubt that a meter can be converted to read properly with a 1.5v cell, my concern would be with the discharge curve of the cells. Mercury cells pretty much maintain a constant voltage throughout their life while alkaline and silver constantly lose voltage. My suspicion is that the meter would end up less accurate as the battery voltage drops. Of course, the Gossen adaptor seems to work fine, and I'm sure that the shop would use the same technique, so who's to say.

I find that the best option for mercury cells is to use 625 hearing aid zinc airs. They require a spacer of some kind to make them the same width as a 675 and fit snugly in the compartment, but they're the same battery as a wein cell, except at a fraction of the price. They come in boxes of 6 or so for a few dollars at your local Walmart/whatever.
 
Eugen Mezei said:
... such a thing as converting mercury based lightmeters can not exist. ... Don't throw your money out the window for so called conversions.
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I guess I missed out on this knowledge. Can you please point me to the supporting evidence/data for this assertion?
 
Gumby said:
I guess I missed out on this knowledge. Can you please point me to the supporting evidence/data for this assertion?
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He is mostly right you know. It is simply the fact that most non-mercury cells do not deliver a constant voltage over their lifetime. The simple electronic design of older light meters depends on this fixed voltage and cannot compensate for changing supply voltages.

Silver-oxide batteries do have a sufficiently constant voltage over their lifetime BUT their voltage is too high. You can however make an adapter for that (Gossen do it themselves) or you can follow this document:

http://www.buhla.de/Foto/batt-adapt-US.pdf

So, if you stick to silver-oxide batteries you can convert an old light meter, and maybe calibrate it as well, if the circuitry allows it.

And yes, to forestall questions, I own a Lunasix myself (a gray one) and use silver oxide cells with adapters in that. It matches my recent Gossen Digiflash in readings.

Good luck with your meter.
 
Ronald_H said:
He is mostly right you know.
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Actually, Ron... I asked because I don't think he is right. I am a user of the Gossen Luna Pro (gray) with Gossen adapter and silver cells. Mine never needed "recalibration" to be "accurate". It works just as good as the meter worked with mercury cells.

The part I can agree with is that non-silver batteries have a discharge curve that is inconsistent with usage in a light meter. I can also agree that the air cells have a life-expectancy that makes carrying spares essential.

The statement I quoted is just too excessively absolute and all-inclusive... and appears to be coming from the perspective of a salesman selling old-technology batteries that were banned for environmental purposes. "(happly selling fresh mercuries to anyone contacts him)" says he.
 
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Thanks everyone. I think I am going to purchase the Gossen adapter. The way I figure it, the manufacturer made it, and calibrated it to work with the Lunasix 3. I just hope my meter is still good otherwise (will read properly after I get the batteries).

Do light meters "loose" their calibration over time?
 
Once you get the adaptor in it, I'd test it against a known good meter of some kind. It's not uncommon for such an old meter to be out.

But, you may be lucky. Mine came from a professional studio and is spot on with my dslr.
 
Ronald_H said:
this document:

http://www.buhla.de/Foto/batt-adapt-US.pdf
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Ron, thanks for that link. I've seen this paper in the past (it's been around a while but appears to have been updated) and I will re-read it. A good summary. I still question the graph on page 3. It show air-zinc cell longevity to be greater than all others. Even with the "equal load" assumption that doesn't seem consistent with user reports. Do you know anything about his?
 
Gumby said:
Ron, thanks for that link. I've seen this paper in the past (it's been around a while but appears to have been updated) and I will re-read it. A good summary. I still question the graph on page 3. It show air-zinc cell longevity to be greater than all others. Even with the "equal load" assumption that doesn't seem consistent with user reports. Do you know anything about his?
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It doesn't display longevity, it shows the voltage over the lifespan of the battery.

So air-zinc cell don't last longer, they just remain their full output voltage until they are almost depleted.

So a alkaline cell may last 300 days, and a air-zinc only 100 for a given load, but the air-zinc will still deliver the correct voltage after 90 days. These figures are of course arbitrary!
 
The main problem with air cells is that as long as they are unsealed, the chemistry is being exhausted. As a result, there is a definite lifespan of a few months until the cells are exhausted. Removing the batteries when they are not in use and covering the holes with tape would probably greatly extend their life.
 
This issue has been explored many time on this and many sites, showing the interest people have to get these old meters functioning again.
-Silver oxide batteries are the best replacement for the Mercury batteries but as we know the voltage is to high. Simply, the voltage must be reduced within the meter.
-If you are taking the meter apart anyway, solder a "shottky diode" 1n4148 or equivalent in one of the battery leads. Either lead, just experiment which polarity.
-Simply amazing.
-The battery test should then read in the center of the red. If this is what happens, (in the center of the red) you will find that the meter is likely reading as it would if you were to install mercury batteries. And in my case the meter (Luna Pro) reads exactly as my Luna Pro SBC and my F3 and F4.
-I think I paid $.02 for my diode. Took 15 minutes to install.
 
In the past I used to extremely dislike all Gossen light meters with the exceptions of the shoe mount pilots. This due to my feeling their scales are graphically unfriendly.

Nevertheless upon further investigagion I have found there are Gossen units very user friendly from the visual point of view, and even such for the meters designed for the pro market.

As for the Gossen Lunasix 3, I am sure Quality Light Meters will fix for around $50 (which is a very moderate price for having a meter spot on again)

The other highly interesting feature I know about the Lunasix 3 is its capability to accept the Gossen dual spot attachment - and this seems to be a HUGE advantage.

Cheers,
Ruben
 
Light meters with CDS a bit. With Si-diode not really and selenium cells yes a lot.
However when electronics is getting older the accuracy is getting slightly less. Due to the uA coil meter a Lunasix 3(S) is pretty stable. But after 30 years it's not too bad to have a check. The battery adapter from silveroxide batteries is the best solution for this Gossen meter.
 
I picked one up today at a thrift store, the meter still had the original price tag on it ($69.99 Canadian). I had some 625 batteries lying around and it works... I just have to figure out how far it is off. I'll compare it to my boss' Sekonic this week. Maybe I'll send it off.

I was close to buying a light meter, I'm glad I found one in great condition for a great price.
 
It's off by quite a bit, but it works. I'm trying to see if I can source the Gossen battery adapter in Canada. I'm going to need a bigger camera bag, the one I currently use barely has enough room for my Bessa, extra lens and film as it is and the Lunasix 3 is huge.
 
Lunasix

Lunasix

It weighs nothing! When I put it in the bag with my Bronica S2a and 40mm I can tell no difference!

How many grains of Tri X = 1 pixel?
 
capitalK said:
It's off by quite a bit, but it works. I'm trying to see if I can source the Gossen battery adapter in Canada. I'm going to need a bigger camera bag, the one I currently use barely has enough room for my Bessa, extra lens and film as it is and the Lunasix 3 is huge.
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I am not sure if I should be giving out this information, but I emailed Gossen about getting an adapter for my Lunasix in Canada, and they emailed me back two weeks later and said that they were going to make an exception and send me an adapter free of charge. This is what they did, and I got the adapter on Monday.

You can try emailing them and ask about a Canadian source for adapters. Maybe they will make the same exception for you.
 
Gumby said:
Actually, Ron... I asked because I don't think he is right. I am a user of the Gossen Luna Pro (gray) with Gossen adapter and silver cells. Mine never needed "recalibration" to be "accurate". It works just as good as the meter worked with mercury cells.
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May be. Even if, what cost that adapter? How long is the life expectancy (both on the shelf as in use) of a silver cell?

The part I can agree with is that non-silver batteries have a discharge curve that is inconsistent with usage in a light meter. I can also agree that the air cells have a life-expectancy that makes carrying spares essential.
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Here we agree.
Plus the price question.

The statement I quoted is just too excessively absolute and all-inclusive... and appears to be coming from the perspective of a salesman selling old-technology batteries that were banned for environmental purposes. "(happly selling fresh mercuries to anyone contacts him)" says he.
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I am very sorry you got this impression.
It just happened that looking for a viable solution for my cameras needing a fixed reference voltage (aka mercury oxide batteries) I came across the information GP/Silva still produces mercury cells and "imported" (= a friend travelling there bought them for me) two boxes of these from Asia. The hapilly meant I will be happy helping people using the same cameras as I do and be assured it covers not the intention to get rich out of this "big buck" business. Maybe this would be nice, but it surely will not happen.

As about old tehnology: Isn't this a bit contradictory, especially when stated in the same posting you tell us you use a gray Luna Pro?
Environmental purposes: 1. Used in a lightmeter or camera (even when it also supplies the shutter magnet) a mercury lasts about 10 years. How many Zn-Air cells will you consume in these years? Ofcourse they have no heavy metal, but they need to be produced. 2. How many mercury oxyde batteries could you produce from the mercury contained in a single neon tube? (Yes they intend to forbid tungsten bulbs until 2012 completly in favor of neon, veeeery environmental friendly.) 3. Returning rates of mercuries were indeed very low (this even worse with used neon tubes), but the main buyers of them were not photographers, they were extensively used in hearing aids where they get rapidly consumed (weeks and not a decade).
So if you will tell me they were forbidden out of environmental reasons I can only answer you that this is a big lie and in my opinion they were forbidden as it was in the interest of the industry. From the tehnological point of wiev it may be old (so what?) but it was a simple and working solution. A Wheatstone brigde don't need too much components but a pair of diodes and condensators (these also can contain heavy metals, especially if they need to be miniaturised - you don't want to have a bulky camera, do you?), some resistors also need to be produced and silicon production is also not the most environmental friendly.

Oh.. as about "excessively absolute": I have not found any solution that would be equivalent to mercuries in all these 3 aspects: 1. tehnologically (voltage sufficently constant to serve as a reference), 2. commoditiy (a. drop it in the camera and forget about it for the next 10 years, b. no modification to the camera), 3. pricewise (a. Zn-Air or even more expensive Wein cells every 2 weeks, b. expensive adapters). The different solutions replacing mercuries fulfill one or two of the 3 aspects, but noone do for all of them.

Well... this said, who is interested will contact me, who not... nobody forces him. :) I just don't like to be suspected by folks I would make a fortune when I am not, especially not if these persons talk without even asking what I would ask for a battery.

Eugen
 
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