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How accurate is a light meter?


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#1 Karel Bata

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Posted 08 March 2009 - 10:03 AM

I remember reading some years ago in Anton Wilson's Cinema Workshop that light meters (back then) had to be accurate to within + or - half a stop at the point of manufacture. That was the spec. and it meant that you could have two side by side giving readings that were a stop apart (one +half and the other -half) yet both would be regarded as accurate!

Has that half stop standard changed? If so, to what?

And how do you guys check your meters for accuracy?
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#2 David Rakoczy

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Posted 08 March 2009 - 02:26 PM

Modern Meters (should) be calibrated within a 1/10 of a stop. Meter calibration techs such as Quality Light & Metric in the USA do the adjustments.
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#3 Chris Keth

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Posted 08 March 2009 - 07:06 PM

I just check mine against full sun and see if it's reasonable. I have it calibrated fairly regularly, though.
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#4 David Rakoczy

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Posted 08 March 2009 - 07:21 PM

Along with what Mr. Keth has mentioned.. it is common to have a meter party before the first shot.. everyone stick your meter in the middle and see what the average of readings is... if there is a discrepancy between my gaffer's meter and mine.. I go with mine because I (personally) carry two Ambient Meters and will check them against each other prior to arriving on set as well as light an 18% Gray Card.. measure it with an Ambient meter and then check my Spot Meter against that...

..and send them to Quality Light & Metric every year or so.
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#5 Brad Grimmett

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Posted 10 March 2009 - 09:56 AM

it is common to have a meter party before the first shot.. everyone stick your meter in the middle and see what the average of readings is... if there is a discrepancy between my gaffer's meter and mine..

The newer Sekonic meters have a adjustment function where you can dial in your meter to match another one, in tenths of course. I've done this before when shooting 2nd unit. Very handy.
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#6 Karel Bata

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Posted 10 March 2009 - 10:17 AM

Time I upgraded from my Weston V. Damn fine meter. :D
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#7 Hal Smith

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Posted 10 March 2009 - 10:55 AM

..and send them to Quality Light & Metric every year or so.


Ditto!

They also calibrate and repair color meters, last year they brought my Minolta Color Meter II back from the jaws of death.

Quality no longer maintains a store but the lab is still in LA. The address below is for a Mail and More that Quality picks up from, and delivers to, twice daily. When you talk to him directly, be prepared for a borderline command of English. Sometimes it takes a little effort to make certain he is understanding exactly what you're saying.


Quality Light Metric Co.
7095 Hollywood Blvd. No. 550
Hollywood, CA 90028
USA

Tel: 323 467 2265
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#8 Serge Teulon

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Posted 10 March 2009 - 11:34 AM

Does anyone know of a place to calibrate meters in the UK?
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Tai Audio

Metropolis Post

Broadcast Solutions Inc

Rig Wheels Passport

FJS International, LLC

New Pro Video - New and Used Equipment

Willys Widgets

The Slider

Visual Products

Glidecam

Media Blackout - Custom Cables and AKS

Paralinx LLC

Ritter Battery

Technodolly

Gamma Ray Digital Inc

CineTape

rebotnix Technologies

CineLab

Aerial Filmworks

Wooden Camera