From: "Jeff Hovis" <jhovis@uwaterloo.ca>
To: "Color and Vision Network" <cvnet@lawton.ewind.com>
Subject: RE: CVNet - reply (3) to query on easel lamps
Yes, Steve Dain and myself have looked at this issue a few years ago. I
can't find Steve's paper, but I seem to recall that his conclusion was that
any light which would meet the CIE requirements for Daylight simulation
would be acceptable.
I found that any light with a color temperature near 7500 degrees Kelvin
and a general color rendering index greater than 90 would be sufficient for
the D-15 test. (Optom Vis Sci ,72 pg 667) I haven't done a complete survey,
but some of the "natural daylight" bulbs that you refer to tend to have
color temperatures 5500 degrees Kelvin and below. Their color rendering
indices vary between 70 and 90. The cost is directly related to the color
rendering index. The more expensive lamps are sufficient for most color
vision screening and they are certainly better than unfiltered tungsten or
standard daylight fluorescent lamps typically used in office lighting.
Richmond International in Boca Raton sells a desk unit that is used by the
FAA for color vision screening.
It is relatively easy to get just the fluorescent lamps with a 7500 K color
temperature and 90 color rendering index from some of the larger lighting
supply stores. Last time I checked (3 to 4 years ago), they cost around $25
US for a standard 4 foot lamp. I don't know if other sizes are available.
There are still some practical problems with these fluorescent lamps. If
you decide to use them in the overhead light fixtures, then you have to
replace all the lamps in the room. Otherwise you have one bluish overhead
light fixture and the rest of the light fixtures appear pink - it doesn't
look too attractive. You could build a light box if there aren't any desk
lamp sizes available, but those aren't cheap either. By the time it is
built, it could cost as much as a commercial unit.
Incidentally, the older style MacBeth Easel lamps with a color temperature
near 5000 K do not perform as well as some of the fluorescent lamps.
However, I understand that the transmittance characteristics of the filter
in newer style Macbeth lamps is different.
I hope this helps
Jeff
-----Original Message-----
From: Color and Vision Network [mailto:cvnet@lawton.ewind.com]
Sent: Friday, May 19, 2000 2:32 AM
To: CVNetList@lawton.ewind.com
Subject: CVNet - reply (3) to query on easel lamps
Subject: Re: CVNet - reply (2) to query on easel lamps
From: "Mary A. Johnson, Ph.D." <mjohnson@umaryland.edu>
To: Color and Vision Network <cvnet@lawton.ewind.com>
I've always wondered if light sources for color vision testing aren't
incredibly over-specified, which is why they end up costing so much.
Has anyone performed a spectral analysis on "daylight" bulbs that have been
pitched to general consumers interested in the mood-enhancing effects of
natural lighting? In particular, there is a "chromalux" bulb manufactured
by Lumiram, available for about $8, that is proported to simulate natural
daylight.
Thanks.
----------
>From: Color and Vision Network <cvnet@lawton.ewind.com>
>To: CVNetList@lawton.ewind.com
>Subject: CVNet - reply (2) to query on easel lamps
>Date: Tue, May 16, 2000, 4:57 PM
>
>From: "Scott E. Brodie, MD, PhD" <brodis01@doc.mssm.edu>
>To: Color and Vision Network <cvnet@lawton.ewind.com>
>Subject: Re: CVNet - query; sources for easel lamps
>
>The MacBeth Easel Lamp went out of production in the late 1980's. (No
>wonder -- they were charging about $500 for this awkward, heavy
>cast-iron table lamp.) The key "magic" element, the blue glass filter,
>was available separately from MacBeth, but they have sold off the last
>of these, and they are no longer available either.
>MacBeth (as well as Munsell Color) is now a part of "GretagMacBeth" (see
>http://www.gretagmacbeth.com/index.html). They sell a large variety of
>carefully calibrated light sources, most intended for industrial
>applications.
>
>Perhaps their handiest product is the "Sol Source" Daylight Desk Lamp, a
>spring-counterbalanced articulated arm desk lamp, which provides a
>choice of three calibrated color-temparatures by means of a "filtered
>tungsten-halogen source." Over the phone, their sales rep confirmed that
>this is an approved light source for color vision testing, as for the FM
>100-Hue test. The price is $395; delivery takes is quoted as about 8
>weeks. I have no personal experience with this item.
>
>You might also try the "True Daylight Illuminator" available from Wilson
>Ophthalmic Corporation (priced at $286.12 in their 1999 catalog). The
>catalogue entry reads "... provides a light source rating of C.R.I 90
>and 6200 deg K, UL approved." This appears from the photo to be a small
>"Easel Lamp", with a shielded bulb housing which runs across the top; it
>holds a book of color-test plates nicely. Again, I have no personal
>experience with this item.
>
>Hope this helps.
>
>Scott.
>
>Scott E. Brodie, MD, PhD
>Mount Sinai School of Medicine
>New York
>
>brodis01@doc.mssm.edu
>
>
>Color and Vision Network wrote:
>
>> From: "Neil Parry" <nparry@fs1.cmht.nwest.nhs.uk>
>> Organization: University of Manchester
>> To: Hoover Chan <hchan@kirkham.ewind.com>
>> Subject: CVNET - Query on Easel Lamps
>>
>> Does anybody know the source of daylight illuminators
>> like the Macbeth easel lamp? I understand these are no longer
>> manufactured, but perhaps someone out there knows of a secret
>> supply, or a suitable alternative.
>>
>> Thanks,
>>
>> Neil Parry
>>
>> Replies to Neil.Parry@man.ac.uk
>
>
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