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the spotmeter on the Sekonic 558


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#1 Gabriel Cortez

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Posted 05 January 2007 - 06:44 PM

Hi all,


I own the Sekonic L-558 Dualmaster, NOT the "Cine" version. I got the chance of testing it with a kodak grey card, and the incident and the reflected readings (spotting from the card) don't match, as they should theoretically.

The spotmeter reads the greycard about one stop higher than what I get with a normal incident reading of the light falling on the greycard. Then I used my Nikon F80's spotmeter on the greycard and it read just like the incident, thus confirming the offset of the spot on the sekonic.

Now, I've read somewhere on the net, don't remember where exactly, that Sekonic calibrates its spotmeter to 12% instead of 18%. Is that true? And can I trust at least the incident readings to be correct?

I wonder if the "Cine" version has the same problem or this weird 12% calibration on the spotmeter is only for the non-cine sekonics.

And, finally, can I recalibrate only the spotmeter on the damn thing, to read one stop lower to match the incident on 18%? I'll check the manual, but it's gonna take me forever to find it, maybe you guys have a quick answer to this one.

Thanks you very much!








Sorry for the double post, my mistake. :(
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#2 Chris Keth

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Posted 06 January 2007 - 05:30 PM

Chances are, it's your error. Spotmetering a greycard is a very sensitive and error-prone endeavor. A slight tilt of the card can change the reading by a stop or more. The difference between a 12% and a 18% grey is well within the realm of error of reading the card. I personally don't recommend setting the taking aperture of a scene with a greycard. I only use one to shoot at the head of a roll, and in the case, I meter wih the incident meter, set the shooting stop, then pull out my spotmeter and ahve the assistant tilt the card around until the reading agrees with my incident reading. This ensures that the card and my shooting stop agrees.
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#3 Frank Barrera

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Posted 06 January 2007 - 09:37 PM

Turns out that 12-13%grey is what ALL our meters (spot, flash and incident) are set for. This issue is explored in The Hand Exposure Meter Book by Gerald Hirschfeld ASC, Bob Shell, Martin Silverman and Jim Zuckerman. This link discusses the math
http://www.richardhe.../photo/18no.htm

This obviously doesn't effect the use of your incident meter but when using say a Kodak 18% grey scale and a spot meter it is recommended to open up 1/2 stop from the indicated reading.


Gabriel, regardless of the above you should not be getting a full stop difference between incident and spot. If you are infact holding the grey card parallel to the lens of the meter and the meter is approx 30 degrees from the light source and you have 0 reflections then something is wrong with your meter and it needs to be re-calibrated. I do not own the meter you have so I do not know how to perform the self calibration. I would just send it back where you bought it.

Personally, I like to use a separate meter for the separate functions. I suppose this is because I started using meters before the two-in-one was introduced. When shooting film I use a Minolta F spot meter only about 10% of the time. And I am very happy with my incident Spectra IV for the rest.

f
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#4 Gabriel Cortez

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Posted 07 January 2007 - 06:14 AM

Turns out that 12-13%grey is what ALL our meters (spot, flash and incident) are set for.

This obviously doesn't effect the use of your incident meter but when using say a Kodak 18% grey scale and a spot meter it is recommended to open up 1/2 stop from the indicated reading.



Frank,

Thank you for the link, it's most revealing, especially the ANSI value for C.

I just want to point out that 12% grey is precisely a full stop below 18%. So if you've got an 18% greycard and 12%-calibrated incident and spot meters, it would be NORMAL for the spotmeter to read around one stop more light from the card than the incident reading says.

What I don't get is how come everybody else seems to agree that the reflected spot reading from a 18% greycard should be the same with the incident reading?

I mean, I think it's rather important to know where your Zone V actually is. (BTW, even Ansel Adams talks of the mysterious "K factor" in his The Negative)


I wonder if anyone else has other opinions about these things.

Thank you!
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