Gossen Luna Pro F and Digisix

Discussion in 'Exposure Discussion' started by johnnywalker, Oct 23, 2009.

  1. johnnywalker

    johnnywalker Subscriber

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    I have a Gossen Luna Pro F I use with my Toyo 4x5. Before I got the Luna Pro, I used my F80 as a light meter, with reasonable results. The Luna Pro reads consistently one stop under the Nikons, and as a result the pictures are generally underexposed. To remedy this, I set the light meter at half the box speed, which has worked out ok.
    I recently bought a RB67, and ordered a Gossen digisix meter for it, which arrived today. The digisix reads within a hair of the Luna Pro.
    I don't understand why there would be a whole stop difference between the Nikons (all of them, generally irrespective of centre-weighted or matrix) and the Gossens. It's nothing I can't work around, but I'm curious as to why the difference. Perhaps "curious" is not a strong enough word. It bugs the hell out of me.
     
  2. arigram

    arigram Member

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    From the little I know, there is very often a difference between lightmeters depending on how they are calibrated in the factory. If I am not mistaken my Gossen Digisix reads Kodak grey slightly differently than my Sekonic 558, but unfortunately I can't test them now as I have sold the former.
    You can calibrate them yourself so its not a biggie.
     
  3. MattKing

    MattKing Subscriber

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    Do you have a large, even toned surface that is exposed to shadowless light? A painted wall illuminated by a cloudy sky would do.

    If so, try testing all the meters using it.

    It may be that the differences arise from the angle of acceptance of the meters.

    Or it may be that there is a definite difference that you need to compensate for.

    FWIW, my Gossen Profisix and my Gossen Digiflash read very similar. I haven't really checked them against my Olympus OM in camera meters.

    Matt
     
  4. jeroldharter

    jeroldharter Member

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    I think you are comparing apples and oranges between the two brands of meters. They are not set up to read light in the same way. Plus, your Nikon reading will vary with the lens attached. If your Nikon camera+lens meter is calibrated to your film exposure and development then simply adjust the calibration of the Gossen meter to match the Nikon. As long as the two meters are linear over the range of light values you measure then you will be fine. I think that adjusting the Gossen meter calibration would be a better approach than having to remember to adjust the ASA between different meters.

    The Digisix is a gem by the way. When I bought mine, I adjusted the calibration so that it read the same as my Luna Pro SBC which I had been using for >20 years and it works great. In some ways it seems silly to use such a small meter with large format but the weight and bulk savings are significant and it will easily fit in a shirt pocket. I think it is a great meter.
     
  5. johnnywalker

    johnnywalker Subscriber

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    I did adjust the nikon lens so it had the same angle (30 degrees) as the Luna Pro and shot them both off a grey towel, so I don't think I'm comparing apples and oranges. But you're right, the difference between the Nikons and the Luna Pro appears to be linear, so it's correctable. And as I said, the new digisix agrees with the LunaPro so no adjustment between those two is necessary. The Luna Pro F isn't adjustable (by me anyway). The Digisix appears to be adjustable, but I'll try it out with the RB67 and a roll of HP5+ before fooling with it.
    I really like the Luna Pro. In a way I'm glad the Digisix agrees with it, since that means it's probably working the way it is supposed to. I was going to send the Luna Pro off for adjustment when the Digisix arrived, assuming (erroneously) that the Digisix would agree with the Nikons.
    Anyway, it's nothing that I can't work around. The Digisix seems like a great little meter all right. I can't believe how small it is, even though I knew the measurements when I ordered it.
     
  6. Chan Tran

    Chan Tran Member

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    How many different Nikon's did you use to make the comparision?
    I found that the variations among Nikon's (to my dismay even of the same model) are much greater than that of the Minolta meters that I have. The newer Nikon's (once again to my disbelief) have more inconsistency than the older ones. I believe that the Gossen's will read a bit different from the Minolta's but would agree with another Gossen.
     
  7. Lee L

    Lee L Member

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    What metering mode were the Nikon SLRs in? I've found that in an average daylight scene with some variation in contrast, the N8008s and N90s in matrix mode match a Digiflash and LunaPro F incident reading to within readout error. Matrix metering tries to figure out exposures in a sort of 'black box' mode based on a number of factors, including light level, meaning you don't always know how it's interpreting a scene. Try seeing if spot mode or center weighted averaging off a gray card with the SLR is a better match to an incident reading with the LunaPro or Digisix.

    Lee
     
  8. Lee L

    Lee L Member

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    Interesting experiment I just ran with the N90s and N8008s bodies and a 35-70 AF zoom, using a Gossen Digiflash in incident mode, and both bodies in aperture priority auto with an Expodisc calibrated diffusion disk over the front of the lens to give an incident reading of a perfectly diffused medium gray field.

    The Digiflash meter gave f:8 at 1/640 in incident mode.

    The N90s body gave the same readings as the Digiflash in spot, centerweighted averaging, and matrix modes at both ends of the zoom range at f:8.

    The N8008s body gave readings that were 2/3 stop brighter (wanting less exposure) in matrix mode at 70mm (f:8 1/1000), matched the Digiflash within 1/3 stop at 35mm (f:8 1/500), and in spot mode gave f:8 1/500 at 70mm, but f:8 1/250 in spot mode at 35mm. In center weighted average mode, the N8008s matched the Gossen within 1/3 stop (f:8 1/500) at both 35mm and 70mm. This was all done in sunlight on a clear day with lens focused at infinity.

    The N90s reads out shutter speeds in 1/3 stops and the N8008s in full stops.

    Lee
     
  9. jmcd

    jmcd Member

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    I think meters are calibrated to at least two different standards. I have a couple of Weston meters, and a Gossen Luna Pro F. The Westons have been recently calibrated by Quality Light Metric, and the Gossen by Bogen. They match exactly, but are 2/3 stop more optimistic than my Canon F-1, Leica M6, Olympus Om1n, and Pentax Spotmeter, which all match each other almost exactly. The meters in camera give me the exposure I need, so I just compensate the rating on the handheld meters to get matching results.
     
  10. benjiboy

    benjiboy Subscriber

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    The crazy thing is that each meter used on It's own would give you correct exposure I have four meters and find this to be true, It's a case of " a man with one clock always knows the right time, a man with several Isn't sure"
     
    Last edited by a moderator: Oct 27, 2009
  11. Martin Aislabie

    Martin Aislabie Subscriber

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    My Gossen Profi-Six over-reads the light levels by a whole stop compared to my Weston Euromaster and Pentax Spot Meter (both are within 1/3 of a stop of each other)

    It is consistent, so is easy to make allowances for but took me a good while to identify the problem

    I just assumed it was my particular meter - but after reading this thread - perhaps not

    Martin
     
  12. johnnywalker

    johnnywalker Subscriber

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    Well, that is interesting. I tried what you suggested, and measured the light reflected of a gray card with the spot meters on my F80 and F100 and it matches the incident reading from the Luna Pro F and the Digisix. Using the Gossens to measure the reflected light from the grey card results in a one stop under reading compared to the Nikons. The Nikons read within 1/3 of a stop of each other, and the Gossens read within a hair of each other.
    I see the book that came with the Digisix recommends using the incident meter for normal metering, and I think that seems like the safest course to follow.
    Thanks for the tip. I'll have some confidence in what the meters are telling me which should allow the masterpieces to come out of the camera. :rolleyes:
     
  13. BetterSense

    BetterSense Member

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    My F801 reads to 1/3 stops in manual mode.
     
  14. Lee L

    Lee L Member

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    The 'analog' meter scale in the F801s/N8008s finder and top LCD display may read out in 1/3 stop LCD block steps, but your shutter speed display uses the traditional one stop steps, and those are the only shutter speeds you can choose manually. The N90s displays 1/3 stop steps on the numerical readout (e.g. 640) in both manual and auto exposure, and 1/3 stop shutter speed steps are selectable in manual mode.

    Lee
     
  15. eldercaribou

    eldercaribou Subscriber

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