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  1. #1

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    Is something wrong with my light meter?

    OK, please don't flame me because I'm using a digital camera to test my light meter. I recently purchased a Sekonic L-508 off ebay. Once I got it I realized I had no idea if it was accurate or not. I've never used a light meter before. I bought it to use with my three Pentax SLRs. So I sent it to Quality Light Metric Co. which I've read is very good. He said he did make some adjustments and brought it within factory specs. He said he calibrated it at 18% gray.

    So I'm testing it out tonight. The incident meter seems to land pretty regularly around 18%, judging from my histogram (pentax k-5). The graph stacks up just left or directly on the mid-line.

    The spot meter (1 to 4 degree) OTOH is a different story. I played with it outside, pointing at all kinds of things and the result was always a blown out picture. I came inside and spot metered off of a gray card on the wall. The Sekonic gave me a reading of 1/30th, f/2.4 @ 1600 ISO. The incident meter just in front of the card gave me a reading of 1/500, f/2.4 @ 1600 ISO. The incident meter was right within that 18% range. The spot was of course overexposed.

    Is this typical of a spot meter to be that much off? I can dial in a compensation from -9.9 to 9.9, to "calibrate" the spot meter. I know the spot and incident typically read differently, but 4 stops seems like a lot different. So should I send this back to Quality Light Metric or not? If I shouldn't, what compensation should I dial in on the spot meter?

    Sorry this was so long but I'm confused.
    Thanks,
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    Kenton Brede
    http://kentonbrede.com/

  2. #2
    wiltw's Avatar
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    If you meter a gray card with any reflected light meter, the results should be quite similar to what you get with an incident light reading. While the ISO calibration equation allows for a manufacturer-chosen variable value, which can lead to differences in readings between different brands of meters, the results should be within 1EV of each other at the most.

  3. #3

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    If what you say is right, that means your meter is off by 4 stops. They are supposed to agree pretty closely. If you have an 18% gray card and stand in front of it. Place your meter in incident mode and point away from the gray card and read. Then, place your meter in reflective mode and point to the gray card and read. Both reading should match pretty closely. Just be careful of your own shadow. You shouldn't have to compensate at all.

    But, since you said your meter was professionally checked and calibrated and it's your first time using any light meter, I think re-checking of checking method is in order.

    I have a L758 and I've only used 508 few times, so I'll have to look up where the controls are.

    When you go from incident to reflective/spot, you need to switch the meter. The switch is located on the right side of the meter and around the eye piece. You rotate it. Are you doing that? When you do, at middle top of the display, dome icon for incident and something that look like a triangle for spot should show. Does it?

    Let's do that much and see....

    By the way, let's take your DSLR out of equation for now. It's not calibrated to 18% and we need to first check if your meter agrees with itself.
    Develop, stop, fix.... wait.... where's my film?

  4. #4
    wiltw's Avatar
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    If you meter a gray card with any reflected light meter, the results should be quite similar to what you get with an incident light reading. While the ISO calibration equation allows for a manufacturer-chosen variable value, which can lead to differences in readings between different brands of meters, the results should be within 1EV of each other at the most.

    If I compare my Minolta Vf incident meter to my Minolta Spotmeter F pointed at 18% gray card compared to my Canon dSLR pointed at 18% gray card, all three readings match each other. But I consider that more 'luck' than 'expectation'.

  5. #5

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    OK, you guys are going to get a kick out of this one. Boy am I red in the face. When I was spot metering I was looking through the wrong end. I switched ends and now the readings match. You guys telling me the readings should match up pretty close helped. As I was testing again, this time I reversed the ends and the reading was much closer. I had looked at the manual but it wasn't real clear which end to use. In my defense I've never seen anyone use one, and this is the first meter I've ever seen.
    Thanks,
    --
    Kenton Brede
    http://kentonbrede.com/

  6. #6
    MattKing's Avatar
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    Quote Originally Posted by kbrede View Post
    OK, you guys are going to get a kick out of this one. Boy am I red in the face. When I was spot metering I was looking through the wrong end. I switched ends and now the readings match. You guys telling me the readings should match up pretty close helped. As I was testing again, this time I reversed the ends and the reading was much closer. I had looked at the manual but it wasn't real clear which end to use. In my defense I've never seen anyone use one, and this is the first meter I've ever seen.
    Thanks,
    Well this did make me smile .

    I wouldn't feel too embarrassed, except for one thing.

    It is always good to carefully read the manual first.

    Just in case: http://www.sekonic.com/downloads/L-508_English.pdf

    Have fun!
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  7. #7
    DWThomas's Avatar
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    Even if it reddens the face, it's comforting to know there's a logical explanation! I have an L-508 and I'm pretty happy with it. It seems so complicated I have to occasionally embarrass myself and read the manual while working in the field.

  8. #8

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    Hehehehehe......
    Develop, stop, fix.... wait.... where's my film?

  9. #9

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    Don't be embarrased!

  10. #10
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    Quote Originally Posted by kbrede View Post
    OK, please don't flame me because I'm using a digital camera to test my light meter.
    I have often thought a digital camera is the best type of light meter.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

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