Meter accuracy

Discussion in 'Exposure Discussion' started by Mirko Lazzarin, Oct 30, 2009.

  1. Mirko Lazzarin

    Mirko Lazzarin Member

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    Good afternoon everyone,
    Here is my problem:
    I got recently a used Sekonic L308 (fo free, at least) after my old Weston master passed away. I thought to rely for once on a digital system rather than an analogic (never again!!).
    I went out shooting few 120mm films, giving maximum attention to expose correctly for shadows, checking the contrast range, etc etc etc (a very rudimental zone system application :rolleyes:smile:..I developed, as always, my films (Fomapan 100 in rodinal 1+25)...and the result was almost a disaster with the films underexposed, I'd say at least 2 stops.
    Would it be possible that the meter is in need of a testing procedures for its accuracy?? Unfortunately I do not have any othe meter to compare the readings and at the moment I cannot send it anywhere for testing.
    Is there any way/procedures to check its accuracy??
    I am pretty lost...and bothered.
    Thanks a lot
    M
     
  2. Denis K

    Denis K Member

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    Correct me if I'm wrong but isn't the L308 normally an incident meter. Does it have the integrating sphere? How were you using it for shadows and the zone system?

    You could always compare it to the Sunny 16 rule. Take it out in the sun, set the ASA to some known value and see if the reading comes out 1/ASA at f/16. It would be hard not to see 2 stops of error.

    Denis K
     
  3. bobwysiwyg

    bobwysiwyg Subscriber

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    It sounds like, for some reason, your exposure was off quite a bit. Without another meter of some sort to compare, I wonder if you could use a gray card and see if the meter will at least produce a setting somewhat close to the sunny-16 rule anyway.
     
  4. Mirko Lazzarin

    Mirko Lazzarin Member

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    Hi Denis,
    Reflective as well..Unless I am doign something wrong, but once you slide the sphere you have a reflective reading
    About Sunny 16 rule...I live in Ireland, this means I have to wait long for a bit od sun :D
     
  5. Mirko Lazzarin

    Mirko Lazzarin Member

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    Yep, I was thinking to buy a grey card...Thanks bob
     
  6. rmolson

    rmolson Member

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    Lacking a gray card to check a meter I have used a healthy look'g green lawn in the summer. IT has about 18% reflectance and in an emergency should be close to the sunny 16 rule too.
     
  7. Denis K

    Denis K Member

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    You don't need a gray card with an incident meter. Just slide the sphere in place.

    BTW, You are right, the L308 has a reflective reading angle of 40 degrees when in that mode.

    Denis K
     
  8. Martin Aislabie

    Martin Aislabie Subscriber

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    The Sunny 16 rule doesn't work for us in the UK or Ireland :sad:

    Try Sunny 11 instead - much closer to reality :smile:

    Alternately, there are a number of active and freindly Irish APUGers you could perhaps team up with to compare meter readings

    Martin
     
  9. BrianL

    BrianL Member

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    Of course it works. You may just have to use f/.95 all the time. You can hit the local photo store and test drive a camera and compare the meter to it. I've done it from time to time and the sales person never objected but, I always bought a little something to compensate, even if a set of batteries, a filter and film. Last time I did it of course I ended up buying a Oly E-500 kit but, that's another story.
     
  10. Ronald Moravec

    Ronald Moravec Member

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    Quality Light Metric in Hollywood, Ca will repair the Weston.

    George does fine work.
     
  11. Eising

    Eising Member

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    I have the same meter. It took me a while to figure out how to use it properly. What I usually do is slide the disc over, and measure the light source (e.g. the sun or sky) then I compensate for whatever light my subject is in. If my subject is in the shade, I compensate about four stops.

    I wouldn't worry too much about the zone system with an incident meter, as it is nearly impossible to meter the zones without a spot meter.
     
  12. Jose LS Gil

    Jose LS Gil Member

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    If memory serves me correctly. The back of your hand, talking about a Caucasian person, is in Zone VI. If you expose for Zone V or 18 % gray, your exposure will be off by one stop. Also, if you have a point and shoot digital camera, you can set the ISO to your film speed and use that as a general light meter. I had to do that today as all four of my meters, two old Pentax spot meters and two old Weston II meters, are either dead or needing calibration.

    One person stopped by while I was setting up my Crown Graphic and he showed me an app on his iPhone that can give you an exposure using the iPhone's camera. Granted, I don't know how accurate that app is. I also asked him, how accurate it was and I don't think he had relied on it for his exposures.
    Personally, I prefer an analog meter over a iPhone app.
     
  13. Martin Aislabie

    Martin Aislabie Subscriber

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    You can "Zone" with an Incident Meter

    See Phil Davis - "Beyond the Zone System"

    Martin
     
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  15. wiltw

    wiltw Subscriber

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    Regardless of race, the PALM of the hand is fairly consistent in brightness at approximately Zone VI.

    I metered my own palm vs. 18% gray card and measured precisely +1.3EV difference.
     
  16. Ian Grant

    Ian Grant Subscriber

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    On two Easter APUG get together (UK) a few of us tested some meters, and we found the readings to be remarkably similar, not even 1/3 of a stop different, that was Gossen, Sekonick, Pentax & Minolta.

    My own meters (UK) a Luna Pro SBC used with the incident light cone cone and as Pentax Spotmeter V, or capital Spot meter, and this year a Minolta gave the same reading, as did the CDS meter of my Yashicamat 124. My DSLR amtched as well :smile:

    Ian
     
  17. pentaxuser

    pentaxuser Subscriber

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    Yes sunny f11 at best and at this time of year probably only between 11:00am and 3:00pm or 10:00am and 2:00pm tomorrow when the clocks go back an hour.:D

    pentaxuser
     
  18. BetterSense

    BetterSense Member

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    This is what you get for relying on ANY meter. If the new meter recommended exposures 2 stops different than the old one, you should have noticed. If you didn't, then apparently you don't interpret your light meter's reading and just plug its recommendations in your camera. You should always take the reading your light meter gives you about as seriously as a politician's promise. It always needs interpretation.
     
  19. jerry lebens

    jerry lebens Member

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    All light meters have their own foibles. I've had a L308 for about ten years and previous to that I've used Gossens, Westons, Leicameters and several more that I don't recall. I've got the L308 wet in the rain and kicked it across several studio floors (black floor & black meter = bad combination) but it still comes back for more. I don't wish to sound rude, but it may be that you've set the meter wrongly or that your not pointing it at the tonal areas you're trying to measure accurately - you may, for instance, need to get closer to the area you're measuring.

    It's also possible that your new meter is inaccurate, but I doubt it. More likely, you've established a 'zone system' that works with your old Weston but no longer holds with your new meter. For a zone system to work it requires a 'closed system' with consistent components. It may be that, in setting up your old system, your Weston was consistently inaccurate (compared to standard) and that you then - unknowingly - compensated for this in development... A zone system may work well within it's own confines but fall to pieces when you inject a new component ; it could be a new film or a new camera, or a new light meter or a combination of all three...

    I suggest you discard the figures you've derived in your old system but, using the same methodology, start again - set up a new set of calibration tests and see where that takes you.

    Regards
    Jerry
     
  20. DanielG

    DanielG Member

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    And you do good in doing so. This iPhone App usually is at least one stop off. Sadly one can never tell wether it is one too bright or too dark this time. :sad:

    Kind regards

    P.S.: Hello APUG :wink:
     
  21. benjiboy

    benjiboy Subscriber

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    This is just an observation- but I think it has to be said, many people who are getting unacceptable exposed results from their light meters automatically blame their light meter and it's accuracy not their lack of understanding of the basic principals of exposure, and how to use the instrument.
     
    Last edited by a moderator: Dec 1, 2010
  22. tkamiya

    tkamiya Member

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    Seems to me, comparing your meter with a known-accurate meter is the first order of business. Otherwise, you have way too many variables to sort through. Would it be possible for you to do that with a friend or at a friendly local store? Especially with a second-hand equipment, anything is possible.

    By the way, back of MY palm is exactly 18%... wooohooo!
     
  23. Q.G.

    Q.G. Inactive

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    Exactly.

    You need to get to know your meter. And (!) how you interpret what it says to you.
    Both require getting familiar with idiosyncrasies, the meter's and your own, and is not helped by comparing the meter to other meters.
     
  24. benjiboy

    benjiboy Subscriber

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    Different meters use different parameters, and acceptance angles for measuring the light, I have five light meters and if I compare the readings of them on a Kodak grey card they vary by up to a full stop but each individual meter give me correct exposure when I use it, it's a case of a man with a watch knows the time, if he has several he's not sure.
     
  25. rmolson

    rmolson Member

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    sunny 16 rule

    The sunny 16 rule does work, It is not the zone system. But if you are in the field and your meter or battery dies it will get you a workable negative as opposed to coming home empty handed
    I spent the first week in Navy photo school in the 50’ memorizing the sunny 16 rule because as a general rule we didn’t have meters available all the time.
    Based on sea level it breaks down as follows using the film speed as the shutter speed Bright sun ( you can not look at it with your naked eye)harsh shadows f/16
    Haze sun you can look at it soft shadows open up one stop (f/11)
    Cloudy Bright you know it is there somewhere but no shadows ,open up 2 stops f/8
    Cloudy dull getting really dark open up three stops f/5.6
    Open shade open up one stop from normal f/11
    Closed shade open up two stops from normal f/8
    Sidelight open up one stop f/11
    Backlight open up two stops f/8
    Kodak use to publish the Master Photoguide with great exposure dials for just about any condition, I still have mine and once in a while check my expensive and sophisticated meters against it when in doubt.
     
  26. BetterSense

    BetterSense Member

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    If you have to go through all that, why use a meter at all? Why not expend that effort to learn the idiosyncrasies of your meter and how you need to interpret its reading into just learning to do without a meter? That's basically my philosophy. I can never be sure a meter is accurate, and most of the time the reading it gives me needs to be corrected anyway because of my own exposure judgments. So the utility of the meter is only in judging the actual brightness of the light, and I find that that can be judged fairly accurately with experience.