sci.engr.color Google Group

Einstein's Biggest Blunder - - Wasn't??

2010-03-09T21:53:31Z

Einstein's Biggest Blunder - - Wasn't??
a bit more light about it
(click link)
[link]
Enjoy,
Fitz

Magnetism is really -- WHAT?

2010-03-03T21:15:39Z

Magnetism is really -- WHAT?
(click link)
[link]
Enjoy,
Fitz

Re: Condela measurement

2010-03-02T23:37:07Z

Hi Douglas,
you are right - I confused luminous intensity with luminance here,
probably because it's the latter I use measure regularly.
Best regards,
Dieter Michel

Re: Condela measurement

2010-03-02T09:44:10Z

On Mar 1, 11:15 pm, "Douglas G. Cummins"
Thanks a lot Dieter & Douglas
I am going to measure the luminance of a blue LED

Re: Condela measurement

2010-03-01T20:15:16Z

Probably not. You can calculate luminous intensity (Candelas) from
illuminance (Lux) by the formula I (Cd) = E (Lux) x [d (m)]², however
the distance d must be at least 5 times the source diameter. The i1
measures luminance at very close distances (typically the surface of a
monitor or print which is much less than 5x the source diameter).

Re: Condela measurement

2010-02-28T20:11:59Z

Hi Saeideh,
basically yes. As far as I know, the Eye-One is predominantly
made for the calibration of (computer) screens and projectors,
i.e. light sources of relative large size compared to the meter.
It does, however, not have an optical viewfinder, so it's - to my
mind - not that simple to correctly aim the meter at very small light

Condela measurement

2010-02-28T12:49:32Z

Hi
dear friends,
I am going to measure the light intensity with candela unit of a light
source. Would you please let me know whether Eye-One spectroradiomiter
can do it?
Thanks

Re: How to decompose RGB into RGBCMY components

2010-02-28T02:52:12Z

Hi Ahauser,
No spreadsheet, sorry. Do a google for Bruce Lindebloom for info and
equations for converting to and from HSB, [link] has some
interesting information on HSB - historical and mathmatical, and the use of
alpha channel masking. The original SIGRAPH paper by Porter and Duff is

Re: How to decompose RGB into RGBCMY components

2010-02-28T01:11:32Z

Thanks Mike ,
that sounds quite promising.
Without asking for everything do you have a example spreadsheet.xls
that may
provide an example as to your method?
Ahauser
On Feb 25, 6:47 am, Mike Russell <group...@MOVEcurvemeister.com >
wrote:

Not Quite Everything for a Theory of Everything

2010-02-26T14:47:58Z

Not Quite Everything for a Theory of Everything
(click link)
[link]
Enjoy,
Fitz

Re: How to decompose RGB into RGBCMY components

2010-02-24T19:47:56Z

Lab space would be the simplest. Start with two user selectable input
values, the hue angle you want to modify (target angle), and the angle by
which you want to shift the hue (offset angle).
For each pixel, calculate a mask value as atan2(a, b) + K, where K is an
offset to make the primaries line up reasonably well with expectations.

Re: How to decompose RGB into RGBCMY components

2010-02-24T08:26:57Z

grADE schrieb:
The problem is that this is an ill-posed problem. You map a
three-dimensional space onto a six-dimensional one, leaving lots of
ambiguities. For example, the map (r,g,b) -> (r,g,b,0,0,0) would
formally be correct (map RGB to RGBCMY) without any "loss", but it is
surely not what you want, correct? If so, you need give additional

Re: How to decompose RGB into RGBCMY components

2010-02-23T23:07:50Z

Thanks Thomas,
But I am not trying to use a CMY space as you say. I am looking for a
formula
to decompose RGB into 6 individual RGBCMY components so as I can
control the saturation and hue
of those 6 individual vectors. I understand the vectors will need a
soft masking as of course they
bleed into one another.

Re: How to decompose RGB into RGBCMY components

2010-02-23T07:47:54Z

grADE schrieb:
It is first of all an ill-posed question because there is not "the" CMY
space. CMY is defined by the absorption curves of the printer inks, and
results can vary dramatically depending on the inks.
You may, for "ideal inks" come up with a conversion that takes you from
*a* (!) RGB space to *an* ideal CMY space, but I wouldn't expect any

Re: How to decompose RGB into RGBCMY components

2010-02-18T23:42:38Z

Thanks Mike,
This is exactly what I am trying to do.
Is it possible to do this programatically with a Matrix?
I have been performing RGB primary adjustments using 3x3 matrices
and am looking to add an interface that gives me enhanced control of
individual RGBCMY
hue and saturation. I could perform this in RGB, XYZ or LAB space if