Gossen Luna Pro: readings way off

removedacct1 · Jan 23, 2015

I recently bought a Gossen Luna Pro from an acquaintance for $20, and yesterday I installed the Gossen silver oxide battery adapter to correct for the voltage difference. In comparing the Gossen's readings to my Nikons built in meter and my iPhone metering app, the Gossen consistently reads nearly four full stops under the other meters. (Would result in gross overexposure)
Is this meter worth repairing - is it even possible? What would you suggest?

Paul

MattKing · Jan 23, 2015

George Milton at Quality Light Metric: http://www.yelp.ca/biz/quality-light-metric-co-hollywood

I exchanged emails with him in 2012, but get the impression that email is not the best way to correspond.

chip j · Jan 23, 2015

You can adjust the Luna Pro w/the little screw on the back.

removedacct1 · Jan 23, 2015

chip j said:
You can adjust the Luna Pro w/the little screw on the back.

That screw is only for zeroing the Battery Test function, not for making calibration adjustments, or so the manual states.

E. von Hoegh · Jan 23, 2015

chip j said:
You can adjust the Luna Pro w/the little screw on the back.

No you can not. That screw is for zeroing the needle, you remove the battery, press the rocker, and adjust the screw so the needle rests at the zero index, this is explained in the instructions.

There are four calibration potentiometers, two for each range, also IIRC a battery check adjustment - and they are not user-accessible for very good reason.

E. von Hoegh · Jan 23, 2015

paulbarden said:
That screw is only for zeroing the Battery Test function, not for making calibration adjustments, or so the manual states.

See my post above and reread the manual.

removedacct1 · Jan 23, 2015

OK, so - is this worth pursuing or do I just give up on it and buy something modern?

Moopheus · Jan 23, 2015

paulbarden said:
OK, so - is this worth pursuing or do I just give up on it and buy something modern?

A Luna Pro F is basically the same meter with additional flash meter, and works with a standard 9V battery. They're not hard to find under $100.

MattKing · Jan 23, 2015

paulbarden said:
OK, so - is this worth pursuing or do I just give up on it and buy something modern?

What type of batteries have you put into the battery adapter, and how new are they?

removedacct1 · Jan 23, 2015

MattKing said:
What type of batteries have you put into the battery adapter, and how new are they?

I bought the Gossen conversion kit which includes two Silver oxide batteries - presumably appropriate for this application since Gossen markets it as a kit. I have no idea how "new" the batteries are, but I got the kit yesterday and installed it immediately. New enough, I would imagine. The Battery Test indicator lands right smack in the middle of the red swatch, so.....

BrianShaw · Jan 23, 2015

You may have just discovered why the meter hadn't been used for a long time.

They seem to sell for about $50 or so, in allegedly working condition. Having George overhaul it will likely cost twice that, but you'll end up with a perfectly functioning meter that will last a long, long time. I have a real fondness for the Luna Pro (and us one on a regular basis) but probably would scrap that one and find one in better working condition.

John Koehrer · Jan 23, 2015

Paul, Nice meter but in the Chicago area they seem to be going for around $50.00. depending what Quality Metrics
charges should make the decision for you..
If they get $50.. for the repair, you're going to have a very nice meter. Probably with a warrantee of some sort. Another used
meter is an unknown quantity.

Ken Nadvornick · Jan 23, 2015

paulbarden said:
OK, so - is this worth pursuing or do I just give up on it and buy something modern?

My vote is still for something modern. Light meters are analogous to data backups in the sense that their main purpose in life is to confer peace of mind. Both are only worth the trouble to have if you know you can trust their results every single time. And if you begin to have any doubts at all, both essentially become worthless.

It's often the case in these situations that by the time one spends the money to bring a questionable older device* up to the level of trust of a newer device, simply adding 20% more would have covered the cost of the newer device anyway. And that additional 20% premium, when spread over the period you will be using (and trusting) that device, is usually pretty trivial.

Ken

* Or devices, if you end up needing to source several to get one good one.

MattKing · Jan 23, 2015

If you like the meter (I do, and own one) then it probably is worth spending the money, unless you intend to buy a new meter instead.

E. von Hoegh · Jan 23, 2015

paulbarden said:
I bought the Gossen conversion kit which includes two Silver oxide batteries - presumably appropriate for this application since Gossen markets it as a kit. I have no idea how "new" the batteries are, but I got the kit yesterday and installed it immediately. New enough, I would imagine. The Battery Test indicator lands right smack in the middle of the red swatch, so.....

Wait a minute - are you absolutely certain you're using the correct scale(s) on the calculator dial? There was a guy here a year or two ago who was setting the number from the meter scale on the EV/LV scale, he had a similar problem to yours.

removedacct1 · Jan 23, 2015

E. von Hoegh said:
Wait a minute - are you absolutely certain you're using the correct scale(s) on the calculator dial? There was a guy here a year or two ago who was setting the number from the meter scale on the EV/LV scale, he had a similar problem to yours.

I've considered this a user error issue as well, but here's the deal: I take a reading, which gives a value on the YELLOW scale in the readout window, and i match that value to the YELLOW arrow/scale on the opposite side of the dial (NOT the LW/EV window numbers). And yes - I have matched ASA on all the devices, so its not a matter of misaligned ASA or some such. But the readings I get consistently suggest a shutter speed + aperture combination that is overexposing by 3.5 to 4.5 stops. I'm pretty certain its not just me misunderstanding the device. (I read the manual three times through to be sure)

I think I will just set this device aside and buy a new Sekonic. Maybe I'll look into repairing it some day, but right now, I'm turned off of the idea of this particular meter. Thank you for all the advice.

gone · Jan 23, 2015

Those are accurate meters, when they work correctly, but big and bulky, w/ an interface that cannot be read as quickly as other analog meters. Going to a newer meter won't buy you any greater accuracy. If it were me, I'd buy the meter that I have, a Gossen SBC Super Pilot. Much smaller and less weight, w/ the same great SBC meter cell that will read accurately in very low light. Plus, these have a bridge circuit in the electronics that allows you to use 1.35 OR 1.5V batteries w/o needing recalibration. I have a pair of 1.5V batteries in there that must be at least 5 years old and still work fine. You could sell your battery adapter (never did like the price they wanted for those, and they are not absolutely necessary, as you can use cheap 1.4V hearing aid batteries in most meters for peanuts). Compare the two meters below. The Luna readout is just a complicated nightmare, the Super Pilot can be read in a thrice. If I didn't already have a good one, I'd buy the one on ebay below because it's in such good condition. And it's KEH, so they probably tested it, and for sure will guarantee it.

http://www.ebay.com/itm/Gossen-Supe...300122?pt=US_Light_Meters&hash=item1c4c8b941a

http://www.ebay.com/itm/Gossen-LUNA...660?pt=LH_DefaultDomain_0&hash=item35e3bdf0c4

removedacct1 · Jan 23, 2015

I'm going to assume the CdS cell is unusable and so I have ordered a modern Sekonic Ambient + Flash meter. The flash measuring feature is something I need anyway. No amount of wishing is going to make the Gossen function properly, so I may as well accept that fact and move on.

Alex Muir · Jan 23, 2015

I think your new Sekonic might be the L308s ? I got one recently and it is excellent. Although the LunaPro is a good meter, when you have a working example, I don't think you will regret buying the Sekonic.
Alex

removedacct1 · Jan 23, 2015

Alex Muir said:
I think your new Sekonic might be the L308s ? I got one recently and it is excellent. Although the LunaPro is a good meter, when you have a working example, I don't think you will regret buying the Sekonic.
Alex

Yup, thats what I've ordered. I would have been happy to work with the old Gossen meter - IF IT WORKED - which it apparently didn't. So be it.

jeffreyg · Jan 24, 2015

Since you are getting a new meter, before you toss the malfunctioning one see if it is consistently off by the four stops mentioned. Reset the ISO on the meter to accommodate for the error and you might have a backup meter. The Gossen has an incident dome. I don't know about the Sekonic.

http://www.jeffreyglasser.com/

E. von Hoegh · Jan 24, 2015

paulbarden said:
I've considered this a user error issue as well, but here's the deal: I take a reading, which gives a value on the YELLOW scale in the readout window, and i match that value to the YELLOW arrow/scale on the opposite side of the dial (NOT the LW/EV window numbers). And yes - I have matched ASA on all the devices, so its not a matter of misaligned ASA or some such. But the readings I get consistently suggest a shutter speed + aperture combination that is overexposing by 3.5 to 4.5 stops. I'm pretty certain its not just me misunderstanding the device. (I read the manual three times through to be sure)

I think I will just set this device aside and buy a new Sekonic. Maybe I'll look into repairing it some day, but right now, I'm turned off of the idea of this particular meter. Thank you for all the advice.

That's the way to do it. Another point, I very often see schmutz on the lens in Gossens - this will skew the reading, but probably not as much as yours is off.
Does the metal placque on the bottom show any signs of tampering? I ask because the access holes for the calibration pots are under this.

E. von Hoegh · Jan 24, 2015

paulbarden said:
Yup, thats what I've ordered. I would have been happy to work with the old Gossen meter - IF IT WORKED - which it apparently didn't. So be it.

That's too bad. The LunaPro has been my main meter since about the mid 1980s, and I have a new-in-box spare I like it so much.

removedacct1 · Jan 24, 2015

APUGuser19 said:
I wouldn't chunk it if I didn't want it any more. I'd feed it back into the market, whether EBAY or put it up for free on here, or whatever. Somebody else can make use of it by parts or repair. I've ended up repairing back to usability more "parts cameras" and other pieces that I actually ended up robbing for parts. It's entirely possible there's nothing more than a tarnished pot or corroded wire causing the problem. Or if it is the CdS, then somebody might want it and use the CdS from another meter that had been run over by a train with nothing but the cell that survived. Throwing this stuff away is heresy, and should be punishable.

I don't believe I said anything about throwing it in the trash - that's not my intent, I assure you. I will likely inquire about having it repaired at some point, but right now, I just want a working meter, which is why I've purchased a modern Sekonic. But thanks for expressing your concerns.

removedacct1 · Jan 24, 2015

E. von Hoegh said:
That's too bad. The LunaPro has been my main meter since about the mid 1980s, and I have a new-in-box spare I like it so much.

Agreed. I would happily have made that my go-to meter if it was accurate, but it ain't. :-(

Gossen Luna Pro: readings way off

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