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Tom
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 26, 2006 - 07:57 pm: | 
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I have a Gossen Luna-Pro "S" light meter. This meter consisently overexposes by two stops or more. I have been throught the manual and can't find anything I am doing wrong. The batteries are charged, the meter is calibrated and everthing set correctly. Any ideas??? |
George Welcher
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 27, 2006 - 08:53 am: |
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Your not taking reflected readings with the incident dome in place by any chance, are you? That would give a reading that was overexposed by about two stops. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 27, 2006 - 09:04 am: |
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On what basis are you calculating that the meter is out?
I take it by saying 'charged' that you mean good batteries. However what batteries are you using? this meter was originally designed around the 1.35 volt mercury cell. In the later production run Gossen produced a battery adapter, so that it could take 1.5 volt silver cells. Here in UK the adapter costs £19.95 - complete with cells, from the Gossen distributor. When you send this meter to Gossen in Germany for service, the price includes the adapter - if needed. Note - Gossen can only service the black cased Luna-Six/Luna-Pro range.
You should also note that this meter does not take kindly to DIY recalibration for 1.5 volt cells. I have seen some pretty crap recals from so called pro-shops also.
So bad recal/wrong cells could be your problem. Properly serviced and calibrated this meter is extremely stable and accurate. My 'S' is from the early production run and still meets the design specification. After a complete refurbishment by Gossen about 18 months ago, it looks like a new meter and is still my preferred choice even though I also have a Starlight model. |
Tom
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 27, 2006 - 07:15 pm: |
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I'm sorry, I made a mistake. The meter is "underexposing" by two stops. When I need 1/60 and F8, the Gossen gives me 1/250 and F8. No the incidence dome is not over the cell and the device has two 1.55v SR44W batteries as called for in the instruction book. Thanks for your responses.
Tom |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 27, 2006 - 07:41 pm: |
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If you have had the meter for a long time and it has just started doing this, get it serviced and re-calibrated. On the other-hand; if this is a resent eBay purchase, check that the battery chamber insert is actually the voltage adapter and not just a bit of tube. It is a common scam to just put a bit of tube in the battery chamber and sell with a late model instruction book. It is not always possible to check by looking at the rear data plate for correct battery info - Gossen will provide these free of charge, if asked. |
Tom Hawkins
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 28, 2006 - 05:22 pm: |
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Glenn - This was a new-in-the-box Christmas gift from a few years back. I just started using it to meter a small collection of vintage cameras. Thae data plate on the back lists two 1.55v sr44 batteries. That actual batteries are Panasonic Sr44W batteries and the chamber insert is the real thing. Thanks
Tom |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 28, 2006 - 08:01 pm: |
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Tom,
So this is a hardly used meter that is powered correctly. Therefore I come back to my original opening sentence - with what and how are you getting your comparisons?
Because the majority of my photographic work was in situations that did not allow reshoots, I have always used any TTL system in conjunction with a hand held meter. I have one calibrated/certified Lunasix 3s, a Lunasix F and a Starlight (a new toy!). These meters are within 1/3 stop of each other and the cross checks using all three, mean that I can extend the recalibration period of the 3s.
This may seem over the top, but I worked in an environment that required traceability and ongoing proof of calibration. The bottom line is that I know exactly how all my exposure metering systems vary, from the calibrated standard.
Unless you can trace one of your metering systems back to a calibrated source, you can never be sure which system is reading wrong.
Looking on the bright side, two stops is well within the exposure/processing latitude for colour negative and most B/W films. So unless you use reversal film, you will get acceptable results.
Glenn |
David Ritchie
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 29, 2006 - 03:35 pm: |
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I am not familiar with this particular meter so I do not know if it has a battery check or not. However, I have had a problem of over exposure due to batteries which were just on the verge of showing "no good" and giving an overexposure of about two stops. If you have seen the curve of how these batteries lose their voltage, you will note that there is a short perior of time where the curve starts down but may still have enough power to operate the meter. This was what happened to me as I lost a whole roll of slide film. Therefore, if you have not done so, check the batteries using a checker which will put a load on the batteries. If that proves negative, then I would suggest that you satisfy yourself that all contact surfaces are clean. An unseen and insidious film can build up and give you fits until those contacts are well cleaned. |
Wolfgang AM
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 17, 2006 - 06:17 am: |
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I bought soem Lunasix 3 on ebay a year ago. Even with a battery adapter, which I made myself with a lathe and some diode insertion, the meter was off a lot. So I recalibrated the whole thing. I uses a graycard and some lightmeter (which is itself old and may not be so accurate any more). Additional I cross checked the outcome with my Canon EOS 5 and an old Pentax. There were no mayor differences between the readings and from that point on I used my Lunasix 3 with success.
I know a Luna-Pro is no Lunasix 3 but I must emphasise how important the right battery is with meters. |
Sandy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 31, 2006 - 01:06 pm: |
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What is needed is a one (germanium 0.2V NOT silicon 0.6V) diode drop from a silver cell. Simply insert an OA91 or better an OA47 diode with the black bit towards the negative side of the battery. Be careful, theese diodes do not like excess soldering heat. Also, some recepticles on batteries do not 'take' ordinary solder (like an OM1) in which case a mechanical contact is needed. |
John Phillips
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 22, 2006 - 10:39 am: |
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I have a Gossen Luna Pro SBC that is underexposing in low light by about 2 stops. Did Bogen buy Gossen? |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 22, 2006 - 03:25 pm: |
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No, Gossen is still going strong in Germany.
www.gossen-photo.de
Always understood that Bogen was just the US distributor of Gossen products, but if they have a similar set up to the UK distributor, they will be able to service it. You should note that the factory offers no service scheme for their old Luna Six/Pro meters that have GREY plastic cases (no spare parts available).
Can never understand why Manfrotto products are always labelled Bogen in US. Manfrotto are the designer/manufacturer, Bogen only distribute. Is it a tariff or trade mark issue? |
Paul Ron
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 23, 2006 - 10:31 pm: |
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Now hold on there you kids! I have 3 SBCs and the older luna Pros. An SBC meter uses a 9V battery not a button cell, the other uses the button cells. Check it again? Is it an SBC or the older Luna Pro? |
A 62 year old kid
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 24, 2006 - 02:29 pm: |
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Paul,
The original subject of this thread was the Luna Six 3S/Pro S family. John Phillips joined the thread with a misreading/faulty SBC. He did not however ask directly for DIY help, but questioned Bogen's involvment with Gossen GmbH. I took this to mean he was looking for service info. To my mind the identities of the respective meter types have never been in doubt/question.
Interestingly; it is the older Lunasix 3S that has stood the test of time, being still available.
One of the Kids. |
paul ron
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 24, 2006 - 05:27 pm: |
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sorry. I thought the other fellow was having a battery issue with his SBC. oops. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 24, 2006 - 06:06 pm: |
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Easily done and I will be getting someone jumping down my throat for stating 'the older Lunasix 3S', when I should have said the 'basic Lunasix design/concept has stood the test of time'. The Lunasix 3S came out in 1988, the SBC in the mid to late 70s - I think. The original Lunasix 3 / Luna Pro dates from about 1966.
Anybody know why the meters are called Lunasix in Europe and Luna Pro in US? |
a problem child
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 25, 2006 - 05:54 am: |
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Glenn, sorry don't know anything about the German based Gossen naming game, but I am somewhat puzzled speculating about the counterproductive etymological roots of those names beginning with luna ... Is it a derivative from French "la lune" ? An allegory: Lunatic professionals? Teutonic puns ?
On the other hand the answer is easy, it's German, and that's that! (You may read into this whatever you like, W.) |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 25, 2006 - 10:24 am: |
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I have a very early press release/article from the late 60s. This indicates the Luna name was chosen by Gossen because this meter was the first mass produced pocket instrument that would measure exposure under moon-light conditions. However this may just be journalistic license and your second para may provide the answer. |
