Re: ProfileMaker 4.1.5 LCD brightness question
Re: ProfileMaker 4.1.5 LCD brightness question
- Subject: Re: ProfileMaker 4.1.5 LCD brightness question
- From: Dan Reid <email@hidden>
- Date: Sat, 28 Jun 2003 11:09:54 -0700
on 6/27/03 12:40 AM, email@hidden at email@hidden wrote:
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About adjsuting the white point to ambient lightning:
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> . . . STEP 4.
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Adjust the white point in PM 4.1.5 to the same visual 'color' as your
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ambient lighting (you may have to iterate) then go straight to building the
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profile.
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***
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Don, how does this conform to ISO 12646, wich says we should only have 32 lux
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ambient lightning when working professionally with images on monitors. To me
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the
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white point should be 5000 K when working with graphic arts production, same
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as
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in the "view boths". At 32 lux the ambient light has more or less no influence
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on the monitor (wich is the purpose of adjusting the ambient light so low).
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Or have I missed something here? Is ISO 12646 known and used in the US at all
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amongst repro/prepress people?
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What Don Hutcheson is recommending doesn't conform to ISO 12646 but that
certainly doesn't mean it's wrong. What Don is referring is to balance the
white point of the display to your *viewing booth* not your ambient light.
If you want to follow ISO 12646 then your ambient light *shall be* less than
64 lux and *should be* less than 32 lux. The ambient light should be D50 or
warmer (i.e. D50 or less -- not cooler)
The whole myth, and yes it's a myth, that we should use D50 is because
of many factors that monitor's can never achieve. Quickly you will NEVER
achieve D50 on any monitor. Sure you can calibrate to 5000K but that's
different from D50. D50 relates to spectral distribution at 5000K not just a
white point. Your viewing booths rarely, if ever, will meet the spectral
curve of D50. Tungsten halogen bulbs offer the closest match to D50 with
fluorescent bulbs being the worst. D50 is used as the white point in LAB
calculations because of the even spectral energy across the spectrum.
Don's recommendation visually compensates for the discrepancy of viewing
booths not being D50. It works quite well.
There are a couple monitor profiling packages (BasICColor Display) allow
you to measure the light source and use that as target white point for
monitor calibration. You will still need a viewing booth with a dimmer to
balance the brightness of the booth to the illuminance of the monitor.
Most prepress and printing folks I venture to say don't know about ISO
12646 or ISO 3664 nor really care. BTW both recommend a monitor illuminance
of 100cd/m2 or higher which an ACD is definitely capable of reaching making
it ideal of comparison to a light booth. Less compensation is required at
the light booth to meet the ACD's high illuminance level even after VCLUT
calibration to your target white point.
--
Dan B. Reid
RENAISSANCE PHOTOGRAPHIC IMAGING
Color Management Products & Training for Print, Internet, & Motion Graphics
http://www.rpimaging.com | Toll Free: (866) RGB-CMYK
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