RE: Using a Spectrolino for density measurements
RE: Using a Spectrolino for density measurements
- Subject: RE: Using a Spectrolino for density measurements
- From: Ray Maxwell <email@hidden>
- Date: Mon, 24 Feb 2003 15:05:21 -0800
Boris has done a very good job of answering your question. I would just add
that the density readings given by a spectrophotometer are more accurate and
repeatable than any densitometer that I have ever tested. This is due to
the fact that the spectral characteristics of the illuminate and the sensor
are normalized each time you calibrate it on the white standard set with the
unit. The Status T,I,E, etc. filters are nothing but numbers stored in ROM
in the instrument (they do not change with time). The spectral
characteristics of the typical densitometer change due to the spectral
changes of the bulb, the spectral changes of the sensor due to temperature,
and the fact that physical filters are difficult to make and fade with time.
In short, density measurements using a spectrophotometer are better than
those made with a densitometer.
To the best of my knowledge it is not possible to convert Lab measurements
to density readings. You need raw spectral data. I think you could do an
approximation if you had a profile of the device.
I know that Bruce Lindbloom has a Excel spreadsheet that converts Lab
readings to Dot Gain. Check out his excellent site at
(
http://www.brucelindbloom.com). He has many handy equations on this site.
Ray
P.S. Creo does not manufacture instruments. We bundle some with some of our
systems.
Creo
Ray Maxwell | Senior Color Systems Engineer, Inkjet Printing
4225 Kincaid Street | Phone (604) 451-2700 ext. 2004
Burnaby, B.C.
Canada V5G 4P5
IMAGINE CREATE BELIEVE
>
----------
>
From: Boris Oicherman
>
Sent: Monday, February 24, 2003 11:59 AM
>
To: 'Robert Castles'; email@hidden;
>
email@hidden
>
Subject: RE: Using a Spectrolino for density measurements
>
>
Bob
>
>
KeyWizard calculates the density from the spectral reflectance of the
>
measured sample and the standard response curves, chosen according to
>
the status (e.g. A, T etc) you set in the setup. The result should not
>
be (theoretically) different from one measured by the densitometer with
>
physical filters, so the fact that it is "simulated" should not bother
>
you. Also pay attention on the Absolute/Paper white settings.
>
On http://www.digitalcolour.org/understanding/Density.htm you can find a
>
brief explanation of how it works and an Excel worksheet (at the bottom
>
of the page) which performs the calculations for status T and some
>
other.
>
>
Boris
>
>
-----Original Message-----
>
From: email@hidden
>
[mailto:email@hidden] On Behalf Of Robert
>
Castles
>
Sent: Monday, February 24, 2003 13:27
>
To: email@hidden
>
Subject: Using a Spectrolino for density measurements
>
>
>
Greetings all, I've got a couple of questions that I was wondering if
>
anyone could help me with...
>
>
1.) I'd like to use a Spectrolino to get read in density values from
>
press sheets. I've previously heard that spectrophotometers can't
>
actually measure density values and that any such values are merely
>
simulated. Does anyone have any information on this topic?
>
>
2.) Also, I was wondering if anyone had any input on the best setup (in
>
Gretag's Key Wizard) for reading density (i.e. What filter to use,
>
etc.).
>
>
3.) Lastly, I also heard a rumor from someone that there is an equation
>
that can be used to calculate density from Lab values. Does anyone know
>
of such an equation and of its accuracy.
>
>
Thanks,
>
>
Bob Castles
>
_______________________________________________
>
colorsync-users mailing list | email@hidden
>
Help/Unsubscribe/Archives:
>
http://www.lists.apple.com/mailman/listinfo/colorsync-users
>
Do not post admin requests to the list. They will be ignored.
>
_______________________________________________
>
colorsync-users mailing list | email@hidden
>
Help/Unsubscribe/Archives:
>
http://www.lists.apple.com/mailman/listinfo/colorsync-users
>
Do not post admin requests to the list. They will be ignored.
_______________________________________________
colorsync-users mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/colorsync-users
Do not post admin requests to the list. They will be ignored.