Re: handheld spectrometers sp64 of Xrite and 2600d of Minolta

The EyeOne or i1 is a 45°:0° instrument and as such does not have the
integrating sphere or xenon lamp. Its performance is comparable to the
X-Rite 528 or 532 spectodensitometers but in a smaller package.

It suppports a 380nm by 720nm spectral data.


"Steve" <nospam@xxxxxxxxxxx> wrote in message
news:knq9u2p1gth81krfn5l2b2ju1435nd9rqf@xxxxxxxxxx
I believe the X-Rite sp64 is being phased out after the merger between
X-Rite
and Gretag Macbeth. Does anyone know how the GMB Eye-One spectro compares
to
these spectros?

Steve

On Mon, 26 Feb 2007 22:11:31 -0500, "Danny Rich" <dannyrich@xxxxxxxxxxxx>
put
together some random words that came up with:

Both instruments can provide reliable readings. The 2600d uses a grating
spectrograph with more than 31 sensors while the SP64 uses 31 interference
filters and does indeed interpolate to 31 points (10nm intervals) because
interference filters cannot be consistently produced to exact wavelength
centroids.

So there are two main differences: incandescent lamp & interference
filters
(X-Rite) versus xenon lamp and grating spectrograph (Minolta).

Short-term repeatability means within a minute or two not 1 hour. Such a
long series of readings or readings taken 60 minutes apart constitute
medium
term repeatability and the toleraces there are indeed larger than the 0.05
value you quote. Continuous readings for 60 minutes will heat the lamp and
illumination optics up more than the spectrometer. As a lamp heats it
spectrum changes.

The xenon lamp has a spectral power distribution closer to that of daylight
than an incandescent lamp and will thus render fluorescent materials more
like they appear outdoors. Xenon has a very high flux density - much
higher
than the incandescent lamp and may produce photochromic effects in some
organic colorants. On the other hand, it has more energy in the shorter
wavelengths and will propagate into a material a shorter distance before
being scattered back to the surface.

I have successfully used xenon-flash lamp instruments to measure skin color
and obtain good agreement with visual evaluations of the skin tones.

For reflecting materials, a spectocolorimeter is always better than a
tristimulus filter colorimeter. The 2600d scans from 360nm to 740nm using
40 photodiodes placed at the focal plane of a concave grating spectrometers
so it captures the reflectance down into the near-UV and up to the middle
of
the long-wavelength visible spectrum. All small, portable
spectrocolorimeters use some form of interpolation to convert pixel
position
to absolute wavelength.

Danny Rich

<wverkruy@xxxxxxx> wrote in message
news:1172303002.110877.287810@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi,
Is there anybody who would have some opinions or experience regarding
hand held spectrometers / colorimeters?
I have been considering two models as specified in the subject header.
They are both measuring spectra in 10 nm increments from 400 to 700
nm. Then, they use an illuminant to compute color values.

I am mostly interested in the spectra however, I measure color values
with a Minolta CR400 which is a flashlamp device using 3 filters,
which are I assume a linear combination of the tristimulus curves.

The main difference between the Xrite and Minolta model are I think
that the Xrite uses a continous wave lamp which is on for about 1 sec
during a measurement (it is a gas filled tungsten lamp).
The Minolta uses 3 flashes of a Xenon lamp I believe.

Both companies specify a short term stability of DE 0.05 (Xrite ) or
0.04 (minolta) when measuring a white calibration plate 30 times.
However, I have found a bigger DE when I measure longer (over one hour
approx). I am not sure if my sample (so far it is a simple stack of
yellow papers) changes color due to continued light exposure or if the
grating optics change slightly due to continuous use of the
spectrometer (warming up?).

I try to measure skin color. Skin can rapidly change color when it is
warmed. This is why I don't like a Ocean Optics CW integrating sphere
setup, it gets too warm and changes the skin color too fast, during a
measurement.

Question #2; Does anybody have an opinion on whether a spectrometric
type as described above would be better to determine color values or a
3 filter type (like the minolta CR400). I think the filter type would
be better theoretically because it does not require interpolation
between the 10 nm increments of the spectrometers. When the
tristimulus curves are steep, and your reflectance spectrum is steep
as well, the interpolation may introduce errors. Anyone agrees with
this assessment?

Thanks in advance.
Wim





.

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