[argyllcms] Re: Next argyllcms release
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 14 Jul 2012 15:13:15 +1000
Ben Goren wrote:
> Anything new and exciting to report, or is it still looking like a marginal
> Upgrade with not a whole lot to benefit those of us who own the original and
> already use Argyll?
All the new features are well publicised by X-Rite, so there's not much to
add. One thing I note is that the RevE measurement mode (== "i1pro2" mode)
doesn't support high gain mode, and that in legacy measurement mode
the high gain mode is reduced to a factor of 5 compared to 10 for
previous revisions. Whether this is of any significance, I don't know,
since high gain mode only helps overcome quantisation, and the
measurements are 16 bit anyway. There seems to be some provision
for a UV filtered version, although it's not clear if they are
available, and how that would interact with the UV LED measurement.
The wavelength calibration basically seems to do a wavelength
correction based on the reference LED. Unfortunately I have
no idea about what the basis for this is. Typically spectrometer
wavelength calibration is done using special lamps or with
special reflective references. Generally LED's tend to change
their output level, wavelength and spectral shape with temperature,
although the primary source of heat is the LED itself, so this
aspect can be controlled somewhat in this particular usage.
I'm not sure if it's possible to get LED's with better wavelength stability
than normal, nor do I have access to X-Rite's historical records of
all the i1pro's they've had in for recalibration, to know how often
a shift in wavelength is the explanation for a loss of accuracy.
One aspect that is intriguing me at the moment is what aspect of the
spectrometers optical path can explain a change in wavelength scale,
assuming it is not due to a fault. For instance, if the device had
an interchangeable normal/UV filter (like the Spectrolino had),
does this change the optical path in some way (other than the obvious)
that would change the wavelength scale by a faction of a nm ?
I got the impression that a UV filter is usually only applied to
the illuminant, so I'm a bit puzzled.
Graeme Gill.
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