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Thread: using a spot meter as an incident meter!

  1. #1

    Join Date
    Sep 2003
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    South of Rochester, NY
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    282

    using a spot meter as an incident meter!

    I don't know if anyone else has done this, but curiosity got me to test this...

    You can use any spot meter as an incident meter by simply placing the "Lumisphere" dome from a Sekonic L-398M meter in front of the lens of the spot meter!

    I have tested this with all kinds of lighting conditions and it works great. Since it's almost impossible to judge reading from different meters, I have compared the results between an L-398M, L-718 and Luna-Pro F meters. The results were all withing a 1/3 stop.

    The easy way to mount the dome would be to get a lens cap for the spot meter and make a hole in it to accomodate the dome. Or you could use the cardboard sheet that the dome comes mounted on when new and make a lens cap from more card stock using glue and/or tape.

    Once mounted in front of the lens, the meter works as any standard incident meter. And no, you can't see anything through the spot meter this way, except grey... ;-)

    Just thought some other people could use this info as I like to get both spot and indident reading and sometimes it's just a pain to use two meters...

    One other note. None of the other dome/spheres I have will work. They're all too dark. Only the "Lumisphere" from the Sekonic 398 will work as far as I know...

  2. #2

    Join Date
    Aug 2000
    Location
    Brookings OR
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    132

    using a spot meter as an incident meter!

    I find it works with the dome from my Minolta IVF on a Pentax/ZoneVI Dig. Spotmeter. Problem is, I frequently point my incident meter upward and there is no way to lock in a reading on the Pentax. The meter always has to be read "live". It would be pretty difficult to get your eye behind the Pentax to measure subjects below eye level.

  3. #3

    using a spot meter as an incident meter!

    You can do this with an SLR camera too - that's the invention of George Wallace (expodisc.com - Wallace Photo Products) . He sells these domes even in a flat shape as he found out how to make the flat pannel sensitive to the direction of light. It's a clever and not so much known invention which didn't find too many followers, unfortunately.

  4. #4

    Join Date
    Mar 2005
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    184

    using a spot meter as an incident meter!

    the expo disc products are becoming more useful with the advent of digital photography, since you can effectively use them to set a custom white balance.

    not that anybody takes the time...

  5. #5

    using a spot meter as an incident meter!

    The spotmeter would need to cover with its angle of view the whole diameter of the dome in order to work properly. As this is not the case it only works when the main light shines on it from directly ahead, not from a side.

  6. #6

    Join Date
    Sep 2003
    Location
    South of Rochester, NY
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    282

    using a spot meter as an incident meter!

    george...

    I thought that too when I first tried it. But the nature of the dome diffuser is... diffusion! It works extremely well no matter what the angle of the light is. If it didn't, I wouldn't have bother posting the info...

  7. #7

    using a spot meter as an incident meter!

    Rich, the function of the dome is not only to diffuse the light but to capture the appropriate amount of light when it comes from an angle (that's why it must be a dome and not just a flat diffuser !). If the sensor's angle of view doesn't see the whole diameter of the cupola it cannot measure the light comming on the dome from an more extreme angle - it measures just a small part of the dome's surface, the rest is invisible for it. That's why it cannot measure properly. And a spot meter (espescially if it is a 1 spot meter) sees just the top surface of the dome, not the whole dome.

  8. #8

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    using a spot meter as an incident meter!

    george... Have you tried it??? Argue all you want, but I've tested it, it works fine and I've made two dome/lens covers for my spot meters and will happily use them. You can not use this idea. That's fine...

    Without doubt there can be certain lighting situations where the spot/dome combo may give a false reading, but that applies to every single design of every light meter made. I have tested this idea with as many lighting conditions as I could think of and it works. The only obvious flaw would be is there was a small spot of bright light falling on the center of the dome where the spot meter reads, and that's a pretty absurd lighting condition and would be considered operator error!

    Noone is forcing you to use a dome on your spot. It works so well for me and solved the problem of carrying a seperate incident meter that I thought I'd share it with other in the same situation. For 10 bucks new and a 1.50 used, I can have an incident meter with me without carrying another meter...

    What more can be said. It works, I'm _very_ happy with it and all I hope is that someone else finds it useful. If you don't like the idea, don't use it...

  9. #9

    using a spot meter as an incident meter!

    "The only obvious flaw would be is there was a small spot of bright light falling on the center of the dome where the spot meter reads" (Rich) - wrong again , it's just the opposite because in this exact condition the meter would read this falling light correctly as it falls on the part of the dome where the sensor sees it. It is when the light falls on the part of the dome where the sensor cannot see it (because of its limited angle of view) that it reads incorrectly. And yes, I constructed a dome for two of my SLR lenses some 15 years ago and use it instead of an incident exposure meter. Of course, there it works perfectly as the lens covers the whole diffusing sphere with its angle of view. That's why it works.

  10. #10

    Join Date
    Sep 2003
    Location
    South of Rochester, NY
    Posts
    282

    using a spot meter as an incident meter!

    george, give it up until _you_ do the testing! I was/am right. Any major light difference between the exact center of the dome, be it a dark spot or a bright spot would produce an error in the reading.

    Fine, according to _you_ this whole idea doesn't work. Then DON'T USE IT! and quit at that and leave the rest of us alone!

    _I_ tested it for two days under every concievable lighting condition. It works as I stated, within 1/3 stop of three extremely accurate incident meters. So it doesn't work for _you_ even though _you_ never did the testing...

    Like I said, I'll be using it, and quite accurately. You don't use it... We'll all be very happy...

    By the way, NO 35mm behind the lens meter will meter totally evenly across the whole film area. So by your own words, your system can't possible work on the SLR either... Ya can't have it both ways... Just give it up and let the rest of us use or not use this as we feel fit...

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