[argyllcms] Re: Using an i1 to measure FWA content?
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 09 Feb 2010 08:09:46 +1100
Martin Weberg wrote:
2010/2/8 Graeme Gill <graeme@xxxxxxxxxxxxx>:
Martin Weberg wrote:
For completeness, here we go again using v1.1.0. Notice the bump in
plot 2 (St. dev. at 410nm is 0.2 (n=3)).
It would be interesting to know how the bump is created, but
without that paper to measure it is difficult to track down.
Something I could provide, besides the paper?
Probably the spectrum of the paper measured without the UV filter
will be enough.
readings contain no UV (10-400nm) I thought it was interesting that
the Spectrolino fitted with UV filter produced higher reflectance then
without filter below 420nm.
On thinking about this some more, I can see only two possible
explanations:
1) There is something different about the instrument calibration
for UV vs. no UV filter. Measuring the calibration tile may
reveal whether this is the case.
2) There's some level of up-conversion fluorescence, or similar
going on. If it really is up-conversion fluorescence then this
would be difficult to model, since it is typically non-linear
(two-photon absorption),
The "or similar" would have to be something like the high level
of illumination at the fluorescent emission wavelengths suppressing
absorption at shorter wavelengths. Fluorescence saturation
may behave like this, but it is also non-linear and typically
only happens at very high illumination levels.
Graeme Gill.
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