Re: 5000° K Full Spectrum Lighting
Re: 5000° K Full Spectrum Lighting
- Subject: Re: 5000° K Full Spectrum Lighting
- From: "dpascale" <email@hidden>
- Date: Sat, 1 Mar 2008 16:26:01 -0500
Richard,
Here are two point of views: (these definitions may change with updates in
the standards):
-------------
IEC 61966-2-1
Colour measurement and management in multimedia systems and equipment -
Part 2.1: Default RGB colour space - sRGB
ambient illuminance level
The illuminance level due to lighting in the viewing environment not from
the display measured normal from the display faceplate at a typical viewing
distance.
-------------
PIMA 7667:
Photography - Electronic still picture imaging - Extended sRGB color
encoding - e-sRGB
ambient illuminance level
illuminance level due to lighting in the viewing environment, excluding that
from the display, measured in the plane of the display faceplate
-------------
For both standards:
The reference ambient illuminance level shall be 64 lux. (-) ... and the
chromaticity should average to x= 0.3457, y = 0.3585 (that of CIE illuminant
D50).
I personally prefer to place the measurement on the faceplate (PIMA 7667)
looking out, but I would make sure I am not blocking the field of view when
measuring, and I would leave a few sheets of paper on the desk if this is
the typical condition.
Danny
email@hidden
----- Original Message -----
From: "Richard Frederickson" <email@hidden>
To: <email@hidden>
Cc: "dpascale" <email@hidden>
Sent: Wednesday, February 27, 2008 12:44 PM
Subject: Re: 5000° K Full Spectrum Lighting
>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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