Re: Detecting fluorescence [was: FA Papers (was: difference hp Z2100 and Z3100)]
Re: Detecting fluorescence [was: FA Papers (was: difference hp Z2100 and Z3100)]
- Subject: Re: Detecting fluorescence [was: FA Papers (was: difference hp Z2100 and Z3100)]
- From: <email@hidden>
- Date: Thu, 22 Mar 2007 21:32:21 -0500
Marco,
And there is yet another method which I developed using a
white target as a reference. You simply take a picture of
a white target against the unknown paper; of course, this
white target has to be non-fluorescent. When importing the
image, you do the white balance either on the target or on
the paper.
Case 1: WB on target, paper is bluer when fluorescent (as
seen on resulting RGB coordinates)
Case 2: WB on paper, target is yellower when the paper is
fluorescent
The advantages of this method are:
-No need for special instrumentation (black light or
spectro)
-Use any camera (photographers usually have one of those
;-) )
-You use the ambient illumination, which means that you
can do the test BEHIND a glass window to see if the effect
is less.
The disadvantage are:
-No "standard" illumination.
However, the evaluation of fluorescence will be quite
different between tungsten, xenon and LED based spectros.
The xenon light of a camera flash should be equivalent to
the xenon based spectro, more readily available, and more
standard betwen manufacturers.
Additional advantage
-If you have a blacklight, illuminating the white target
with the paper will give you a reference and make the
comparison even more eye-popping.
For more information, you can read this pdf on the
subject.
http://www.babelcolor.com/download/AN-2 How to identify UV-enhanced paper.pdf
Regards,
Danny Pascale
email@hidden
www.BabelColor.com
On Wed, 21 Mar 2007 22:08:26 -0700
Marco Ugolini <email@hidden> wrote:
In a message dated 3/21/07 9:13 AM, Andrew Rodney wrote:
On 3/21/07 9:08 AM, "Anthony Sanna" wrote:
Some questions: Andrew... What's your OB-Checker? Is
this a hardware
store assemblage?
I use a battery operated Fluorescent black light for
location work. I could
as Robin did, use my Spectrolino.
Those are the two ways I use too: either a black light,
or my EyeOne Pro Rev
B (non UV-cut) to look for a "bump" in the spectral
energy distribution of
the paper base in the area around 440nm.
Personally, I haven't yet fully tested the reliability
of judging
fluorescence by reading Lab values off the paper base
(in which a negative
b* value is regarded as a sign of fluorescence, and a
positive b* value is a
sign of its absence).
Marco Ugolini
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