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Re: 5000° K Full Spectrum Lighting
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Re: 5000° K Full Spectrum Lighting

  • Subject: Re: 5000° K Full Spectrum Lighting
  • From: Richard Frederickson <email@hidden>
  • Date: Wed, 27 Feb 2008 12:44:49 -0500
Richard,

If you do not compare the monitors agains the viewing booths, D50 is not required for your monitors. Others, I am thinking of Roger Breton here ;-) , may argue, but as long as you are adapted, D50 or D65 is OK. If you "walk" to the booth, you will get adapted to the booth's D50 within a few seconds (as you are walking towards the booth...). In any case, if your users are OK with D50, then just keep it this way (as long as they do not see a D65 monitor in their field of view, which will make their own monitor look yellowish).

According to ISO 3664, the color temperature of the ambient light should be, :
"The correllated colour temperature of the ambient illumination shall be less than or equal to that of the monitor white point."


With such a requirement, your 4000K tubes would do OK, as well as your lower cost 5000K and the more expensive GTI ones, but all would be out in terms of illumination level. In such a context, the more expensive tubes are not required since they are not udes for color assessment.

You bring up a good point with the monitor white point.
As much as possible, I try to match the monitor's "white" to a sheet of paper sitting on the work surface. So in that regard--yes, it would not matter if the ambient light is 4000° K or 5000° K.


As Karl noted, the suggested ambient level is 64 lux, preferably 32. My suggestion of 100 was just a compromise betwen your measured 390 lux and the cave level! Some fluorescent fixtures can be dimmed; I would check the color temperature when dimming though.

I have not seen any protocols for measuring the light level at the work surface.

I measured the ambient light at the monitor with the eye-one at the center of the monitor and facing straight at the operator (looking horizontal, as is shown in the Eye-One Match illustration).

For the measurement at the keyboard, however, I faced the instrument straight up toward the ceiling. This could account for such a high value (390 Lux at the keyboard vs. 74 at the monitor). Is there a better way to measure illumination at the work surface?

Thanks,
Richard


Danny
email@hidden

----- Original Message ----- From: "Richard Frederickson" <email@hidden>
To: <email@hidden>
Sent: Wednesday, February 27, 2008 9:48 AM
Subject: Re: 5000° K Full Spectrum Lighting

Karl, Danny, and the list,
Thank you for your thoughtful comments. A little more background explanation may be in order.

I'm not trying to turn our illustration studio into a giant D50 view box. We have a GTI viewer with our scanning workstation and any critical color/prepress color judgements are done using that viewer. I visited a vendor of ours, and their entire facility is 5000° K--using everything from fluorescent tubes in the office/design areas to mercury vapor in the production warehouse space.

I'm simply interested in providing our graphic designers and photographers with the most appropriate working environment as possible for the overall space and for general black and white and color work. I think I've won the argument for calibrating everyone's monitors on a regular basis (~D50), as well as neutral gray furnishings and walls. The last piece of the viewing environment to address, then, is the general illumination.

We are located in a government facility, which mandates the use 32 watt "energy efficient" lights and are currently using warm white fluorescent tubes. My instinct tells me that the 5000° K "full spectrum" lamps should be better than the 4000° K we're getting from our lowest-bid office lamps.

Employee comfort and avoiding eye fatigue is a major concern--so I don't want to turn the studio into a bat cave. I do have some ability to moderate the lighting within the scanning area, and it will be at a lower level of illumination.

How much is enough, and where does it become too much is the main concern of my boss.

Any of your insights are greatly appreciated,
Richard


Hi Richard, Danny,


Am 26.02.2008 um 23:33 schrieb dpascale:

Richard,

Do you intend to illuminate the area around your monitors with 5000 K light?
ThatZs whaZs recommended in ISO3664 and 12646


If yes, are your monitors also at D50? (or somewhere between D50 and D60)
again, ISO 12646


Do you intend to compare your prints against your monitor? If not, then buy these low cost tubes and keep the ambient level low (100 lux recommended). If yes, read what follows.
Even lower, if you want a good comparison, your viewing light must e 500 lx ± 125 lx (ISO3664), this requires a monitor luminance of 160 cd/m2 (± 40) and your ambient light must be below 64 x and should be below 32 lx.


The required illumination for correct viewing assessment, 500 lux+, is too high to be used as ambient (even your 390 lux is way too high for many).
This is absolutely correct, because the ambient light drastically reduces the contrast ratio on your monitor.

Thus, you need a separate, somewhat confined, viewing booth. You will also need to adjust your booth light output so that the luminance of the viewed print matches your monitor luminance (typically 100 to 160 cd/m2).
with 100 being too low, the range is 120 to 200 cd/m2)


If you compare your prints under a 5000K lamp near your monitor, your monitor better be at 5000K also. If your monitor is "far away" from your viewing booth, a D65 calibrated monitor will be OK.

If you critically compare printed material with printed proofs, without a need to compare the prints against a nearby monitors, then a room full of fluorescents at 5000 K, with much more than 500 lux, is the way to go (2000 lux is recommended, which is quite bright !).
S but typical for a standard viewing booth.


You better use less of the more expensive fluorescents and place them at select locations where they do not interfere with the monitors (a booth, or a low hanging fixture is preferable to a ceiling fixture). And keep all the other lights off (the window shades also if applicable). The indirect illumination from the booth areas should be enough to work comfortably. If not, individual desk lamps should be used when required.
Keep in mind, though that the lamp fixtures - reflectors, deflectors - also have an influence on the spectrum. So, a professionally made lamp with certified (close to) D50 light would be the first choice. BTW, D50 is not a full, smooth spectrum, but a specified spectral curve (quite jaggy) that cannot be technically reproduced (within reasoable effort). 5000K Planck is a smooth curve.


And, finally, to add to what Andrew mentioned, fluorescents are fluorescents (!), even the best ones are not perfect, imagine the second tier...

Danny Pascale
email@hidden


Best,

Karl Koch




----- Original Message ----- From: "Richard Frederickson" <email@hidden>
To: <email@hidden>
Sent: Tuesday, February 26, 2008 4:14 PM
Subject: 5000° K Full Spectrum Lighting

My manager and I have had an ongoing discussion for some time now regarding whether or not 5000° K lighting is justifiable in our illustration/photography workstation areas. We do some prepress work and I have a GTI viewer at our scanning workstation. Most of our material is printed in-house (e.g., scientific posters) and our color is important, but not critical.

The folks at GTI quoted me a price of $23 a lamp, which my boss absolutely will not go for. I've seen a number of "Full Spectrum" lamps on the market that are the same color temperature for as little as $6 a tube, and I'm thinking that something is better than nothing. Am I right in this line of thinking and how prevalent is full spectrum lighting in the real world?

Also--beyond color fidelity issues--are there any additional benefits documented about working in this lighting environment?

The corollary question is how bright should the working environment be? I took few quick measurements around the office with my eye-one found a value of 74 Lux at the monitor is about 390 Lux at the keyboard and quite comfortable to work in.

Many thanks for your thoughts,
Richard

--
Richard Frederickson (Contractor)
Scientific Publications, Graphics & Media (SPGM)
Advanced Technology Program, SAIC-Frederick, Inc.
National Cancer Institute at Frederick
Post Office Box B
Frederick, MD  21702
Phone: (301) 846-1546
FAX: (301) 846-6563
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References: 
 >5000° K Full Spectrum Lighting (From: Richard Frederickson <email@hidden>)
 >Re: 5000° K Full Spectrum Lighting (From: Koch Karl <email@hidden>)
 >Re: 5000° K Full Spectrum Lighting (From: Richard Frederickson <email@hidden>)
 >Re: 5000° K Full Spectrum Lighting (From: "dpascale" <email@hidden>)

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