Re: profiling papers with brighteners
Re: profiling papers with brighteners
- Subject: Re: profiling papers with brighteners
- From: Armand Rosenberg <email@hidden>
- Date: Tue, 18 Dec 2001 14:06:35 -0500
To keep the focus: the question I was asking is why the Tek 450
profile was so good in spite of the optical brighteners in the paper.
Just for clarity: an LED (light-emitting diode) is not a laser,
although they are related. If you had a spectrometer with high enough
resolution, you would see the difference in linewidth between an LED
and a laser quite clearly. The linewidth of a laser is much narrower
still -- but often measurements are limited by instrumental
resolution in the real world. It's true that LED linewidths are
narrow when compared to a full visible spectrum as emitted by a
halogen bulb, for example.
My point was that blue LED's have historically tended to be a lot
weaker than the reds and greens (or any wavelength longer than blue,
generally) due to materials issues, which have started to be resolved
only in very recent years. I don't know what type of blue LED is in
the ColorMouse, but those commonly available when it was manufactured
were rather weak, as far as I know. As far as profiling is concerned,
I don't know if this makes a difference or not since I can also think
of various methods of compensating for this shortcoming.
Implicitly, the other question I was raising concerns the LED source
in the ColorMouse, and whether it's better or worse for profiling
than a light source with a more continuous spectrum, as is used in
other instruments.
Armand
In a message dated 12/18/01 11:42:14 AM, email@hidden writes:
I agree, which is why I am confused.
Could these LED's not cover the spectrum sufficiently well? I would
suspect the blue LED's particularly.
The spectrum of a blue LED is a really tight bell curve, that contains no
purple, no green, and no UV... its truely amazing how tight the emission
spectrum of an LED is... rather like a laser.
C. David Tobie
Design Cooperative
email@hidden