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Thread: Spot meter

  1. #21

    Join Date
    Jul 2016
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    4,362

    Re: Spot meter

    Quote Originally Posted by Ricardo Maydana View Post
    Hi, guys.
    This issue of isolation. Leads me to the next question
    Measuring candlelight with the photometer. It has a certain EV value. I have two photometers and they both read differently. How do I know which one is more accurate?
    Greetings


    Enviado desde mi iPhone utilizando Tapatalk

    > Use a camera with a reliable photometer (like nikon F-65) and see what photometer matches.

    > Buy a $ 10 yo $20 cheap Luxmeter, search: https://www.ebay.com/sch/i.html?_fro..._odkw=luxmeter

  2. #22
    Arca-Swiss
    Join Date
    May 2002
    Location
    Phoenix, AZ
    Posts
    124

    Re: Spot meter

    The battery idea is a good one, but another one to look at is what kind of metering cell the meter uses. The earliest spot meters used a CDS cell(Cadmium Disulfide) which had some issues with some kinds or colors of light. It also had memory. If you pointed it at a very bright light, it was like humans and retained that for a while. Look at the sun and you see a bright ball for a while until your eyes/brain sort of let it fade.
    Then came the Gaspd (Galium Arcsenide photo diode). Big improvement. This one also was blessed with a wider light spectrum. It also did not have a memory problem like the earlier spot meters. The soligors, and the Pentax Spotmeter V, were among the CDS types that were common. The Pentax Digital was of the GASPD type and also had few moving parts making it sturdier.

    If both meters are the same model, they should or could be tuned to match. If not, the above info may explain.

    One other point you cannot get a good meter reading through a filter with most spot meters except the Minolta M, Pentax modified by Zone VI, and the later GASPD meters like the Pentax Digital and the new Sekonics.
    For Zone system the Pentax Digital with a Zone system sticker installed is by far the easiest to use.
    Rod Klukas
    US Representative
    Arca-Swiss International
    480-755-3364


    Digital Camera Solutions including R-series Technical Cameras, Large Format View Cameras and Ballheads. 480-755-3364

  3. #23

    Join Date
    May 2015
    Location
    SooooCal/LA USA
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    1,785

    Re: Spot meter

    Then there is the basic test... Bring both outside on a sunny day, meter a grey card with both, one should read close to the "sunny 16" rule, which is in normal bright sunlight, at f16 set, the shutter speed will be the same as the ISO box speed rating, so one meter will be close, but the other not...

    Then a film test with color chromes about right with the highlights and shadows, or with B/W, the neg should have a good balance of shadow and highlight detail... You can fine tune this in later tests...

    Good luck!!!

    Steve K

  4. #24
    (Shrek)
    Join Date
    Mar 2011
    Location
    Montreal
    Posts
    1,666

    Re: Spot meter

    Quote Originally Posted by LabRat View Post
    Bring both outside on a sunny day..
    Part of the issue may be that the analog Pentax V meter reads far into the infrared range. In fact I use mine to shoot infrared, I mount my filter on the front of the meter with step-up rings, take my reading at the lowest ASA setting (I have to use the internal light to see the needle and of course I can't see what the meter is pointing at so I wave it around until I find my spot), then adjust by the number of stops necessary for the film i'm using. My exposures come out perfect every time.


    If you're using a Pentax V to shoot say transparencies outdoors in strong sunlight, I would recommend using an IR blocking filter on the meter, because it has none internally.

  5. #25

    Join Date
    Apr 2004
    Location
    SF Bay Area, California, USA
    Posts
    315

    Re: Spot meter

    Quote Originally Posted by Jody_S View Post
    Part of the issue may be that the analog Pentax V meter reads far into the infrared range.
    I think the Pentax Spotmeter V and Digital use the same silicon photodiode, and both read well into the infrared (the brochures show the response juxtaposed with that of the 1931 CIE observer); the curves appear to be the same. I had a rough spectral-response test done many years ago that pretty much confirmed the advertised curves; the result for my Minolta Flashmeter III more or less matched the curve marked “Visibility” in the Pentax brochure. Neither curve, of course, matches that of a particular film or a digital sensor. In my experience with a fair number of samples of both meters, they track very closely for normal subjects (e.g., a gray card), nearly always within ±1/3 step over the entire range.

    Interestingly, the same is true for my Zone VI–modified Digital, though it diverges from my unmodified Spotmeter V when reading through a red filter.

    So I think the difference Ricardo is seeing is more likely a calibration issue than a design difference.

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