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» Film-Tech Forum   » Operations   » Large Format Forum   » Light meter (Page 1)

 
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Author Topic: Light meter
Ivan Plamondon
Film Handler

Posts: 42
From: Welland, Ontario, Canada
Registered: May 2013


 - posted 01-27-2014 12:08 PM      Profile for Ivan Plamondon   Email Ivan Plamondon   Send New Private Message       Edit/Delete Post 
Can anyone suggest a decent low cost light meter?

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16113
From: Bountiful, Utah
Registered: Jun 99


 - posted 01-27-2014 04:17 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Harkness makes a screen brightness checker that's ok. You should really compare it to a real light meter before you use it just to verify where it reads.

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Ivan Plamondon
Film Handler

Posts: 42
From: Welland, Ontario, Canada
Registered: May 2013


 - posted 01-27-2014 04:38 PM      Profile for Ivan Plamondon   Email Ivan Plamondon   Send New Private Message       Edit/Delete Post 
Thanks Mark

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Ivan Plamondon
Film Handler

Posts: 42
From: Welland, Ontario, Canada
Registered: May 2013


 - posted 01-28-2014 09:04 AM      Profile for Ivan Plamondon   Email Ivan Plamondon   Send New Private Message       Edit/Delete Post 
Harkness is still a bit too pricey for our theatre.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16113
From: Bountiful, Utah
Registered: Jun 99


 - posted 01-28-2014 10:47 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
It's probably the least expensive option available thats made for the job. Even a used Spectra Screen Brightness meter in working condition will set ya back more than the new Harkness.

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Scott Norwood
Film God

Posts: 7966
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99


 - posted 01-28-2014 11:25 AM      Profile for Scott Norwood   Author's Homepage   Email Scott Norwood   Send New Private Message       Edit/Delete Post 
Just the calibration on the Spectra SC-600 is in excess of $200, but it is a very nice unit. You don't want to see the price for a new one, though.

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Paul Mayer
Oh get out of it Melvin, before it pulls you under!

Posts: 3835
From: Albuquerque, NM
Registered: Feb 2000


 - posted 01-28-2014 01:50 PM      Profile for Paul Mayer   Author's Homepage   Email Paul Mayer   Send New Private Message       Edit/Delete Post 
I suppose one will not like the price of the meter I was recently using at Callahan and Christie: the Photo Research Cinebrate. Specifically designed for use with digital cinema projectors, it reads screen luminance and color coordinates. New, it's priced at under $10,000 USD. Still cheaper than a calibrated, used Minolta...

http://www.photoresearch.com/current/cinebrate.asp

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Ivan Plamondon
Film Handler

Posts: 42
From: Welland, Ontario, Canada
Registered: May 2013


 - posted 01-28-2014 02:09 PM      Profile for Ivan Plamondon   Email Ivan Plamondon   Send New Private Message       Edit/Delete Post 
I guess the Harkness unit doesn't seem so bad at $750. Still way out of our price range however.

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Carsten Kurz
Film God

Posts: 3681
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 01-28-2014 02:50 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
I think the Harkness digital screen checker can be bought from other suppliers as well. I also remember there were offers for collective purchases.

Cinema Technology Magazine had an article on the digital screen checker in a past issue.

If you want to go cheaper, a second hand photographic spot meter can used as well after some training.

- Carsten

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Ivan Plamondon
Film Handler

Posts: 42
From: Welland, Ontario, Canada
Registered: May 2013


 - posted 01-29-2014 09:17 AM      Profile for Ivan Plamondon   Email Ivan Plamondon   Send New Private Message       Edit/Delete Post 
Carsten, can you steer me towards a few brands of spot meters? We utilize 7kW Superior lamps.

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Carsten Kurz
Film God

Posts: 3681
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 01-29-2014 04:12 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Depends a bit on what you are actually after. A proper screen light meter will give you familiar units like fL or cd/sqm. A photographic spot meter will usually have a coarser readout, as photographic units are usually f-stops or EV, with 1/2 or 1/3 divisions at best. You will need to do some easy calculations to get fL out of these numbers, and the error may be large. In fact, you could even use an existing SLR or DSLR with a spot meter.

Check e.g. Minolta Spot Meters on ebay. You could even use an incident light meter - always depending on what you are trying to achieve. If you have a proper measurement from an installer and don't change screen, relative measurements are possible.

However, this is the Large Format Forum, so I assume you want this for film projection - you can not be sure that any of these cheaper alternatives do well with the 48Hz flicker of film projectors. My incident light meter does well with it, my SLR does not. Both do well with digital projectors.

- Carsten

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Ivan Plamondon
Film Handler

Posts: 42
From: Welland, Ontario, Canada
Registered: May 2013


 - posted 01-30-2014 10:45 AM      Profile for Ivan Plamondon   Email Ivan Plamondon   Send New Private Message       Edit/Delete Post 
You are correct Carsten. Trying to measure light from a 7kW Superior lamp projected on a 60 by 80 foot screen. Our system is a 70 mm 24 frames per second GT IMAX rolling loop projector.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16113
From: Bountiful, Utah
Registered: Jun 99


 - posted 01-30-2014 01:00 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
I'll second the Minolta idea. I use a Minolta color space meter and it's been very good. For plain old white light measurements on the fly I use my Spectra FL spot meter is what I use, I also have a Spectra that measures candellas.

Mark

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Bobby Henderson
"Ask me about Trajan."

Posts: 10678
From: Lawton, OK, USA
Registered: Apr 2001


 - posted 01-30-2014 01:41 PM      Profile for Bobby Henderson   Email Bobby Henderson   Send New Private Message       Edit/Delete Post 
Is it possible to rent something like a high quality cinema screen light meter for a couple days, or does that piece of gear usually include a human technician, airfare, hotel lodging, etc.?

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Carsten Kurz
Film God

Posts: 3681
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 01-30-2014 02:28 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Forgive me ;-) - shouldn't a place with an IMAX GT projector and a 60*80ft screen be able to afford 750US$ for a light meter?

I may be able to test a few dedicated spot meters on a 35mm machine soon.

- Carsten

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