Spectrophotometer use and material reflectance

Anyone using a spectrophotometer to measure reflectances for use in Radiance? Section 5.1.9 (p304-307) of the Radiance book shows how it can be done. Is this method still used, and if so could you post/email the scripts spct2xyz.csh and xyz2rgb.csh?

Any tips/pointers not already covered in Section 5.1.9 would be much appreciated. We'll be using a Konica/Minolta CM-2600d portable spectrophotometer.

Cheers,

-John

···

-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)

[email protected]
http://www.iesd.dmu.ac.uk/~jm

Hi John,

It is a long time ago that I experimented using a Minolta spectrometer, I think is was in 2000.
At that time I wrote and bundled some scripts and documents, I just put these on the server for you:
http://www.iebele.nl/radiance/callibrate/

Look in this document for "Minolta's spectro-photometer"
You will need these scipts/programs:

http://www.iebele.nl/radiance/callibrate/minolta.c ( just one of my own progs, ...)
http://www.iebele.nl/radiance/callibrate/spct2xyz
http://www.iebele.nl/radiance/callibrate/xyz2rgb

Because most of the page is written in Dutch, here a short help:
( spectraal-q14.txt is a just a file from your spectrometer )

$ ./minolta < spectraal-q14.txt
Convert Minolta photospectrometer spectral data list
Ranging from 400 to 700 nm
This data can be read by spct2xyz
Number of steps in spetcrum : 31
Number of measured items : 20
Writing file Q14-0.spc 1
Writing file Q14-1.spc 2
...
Writing file Q14-19.spc 20

Now check the result:

$ more Q14-0.spc
#nm reflectance
400 0.728000
410 0.799700
...
700 0.933800

Now translate *.spc files to .xyz and .rgb line this:

$ ./spct2xyzQ14-0.spc > Q14-0.xyz
$ ./xyz2rgb < Q14-0.xyz > Q14-0.rgb

I don't know if these scripts still work, or if they are accurate,
hope it helps you a little,

Iebele

···

----- Original Message ----- From: "John Mardaljevic" <[email protected]>
To: <[email protected]>
Sent: Thursday, July 24, 2008 10:41 AM
Subject: [Radiance-general] Spectrophotometer use and material reflectance

Anyone using a spectrophotometer to measure reflectances for use in Radiance? Section 5.1.9 (p304-307) of the Radiance book shows how it can be done. Is this method still used, and if so could you post/ email the scripts spct2xyz.csh and xyz2rgb.csh?

Any tips/pointers not already covered in Section 5.1.9 would be much appreciated. We'll be using a Konica/Minolta CM-2600d portable spectrophotometer.

Cheers,

-John

-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)

[email protected]
http://www.iesd.dmu.ac.uk/~jm

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

Hi again John,

The file in mentioned in my previous mail, spectraal-tmtq14.txt, is not obtained from the Minolta directly.
It is an edited spreadsheet from the Minolta (edited by hand). The input file for minolta.c should look like below, ie. only containing spectral data.

The first integer indicates how many samples are stored in the file.
The next integer indicates the actual sample, followed by a string, followed by all spectral values, in this case 31.

20
1 Q14-0 72.8 79.97 84.35 86.68 87.71 88.45 88.84 89.2 89.45 89.57 89.63 89.69 89.78 90.01 90.21 90.24 90.2 90.13 90.03 89.83 89.71 89.85 90.16 90.71 91.24 91.45 91.57 91.65 91.87 92.4 93.38
2 Q14-1 64.29 65.83 66.84 67.47 67.86 68.23 68.51 68.68 68.81 69 69.17 69.28 69.39 69.51 69.7 70.08 70.43 70.52 70.52 70.49 70.5 70.7 70.98 71.32 71.64 71.81 71.95 72.1 72.3 72.59 73.02
.....
20 Q14-19 4.68 4.55 4.49 4.48 4.49 4.49 4.49 4.46 4.42 4.41 4.41 4.39 4.36 4.32 4.3 4.32 4.35 4.35 4.33 4.27 4.22 4.24 4.27 4.26 4.24 4.22 4.21 4.22 4.23 4.22 4.18

-Iebele

···

----- Original Message ----- From: "John Mardaljevic" <[email protected]>
To: <[email protected]>
Sent: Thursday, July 24, 2008 10:41 AM
Subject: [Radiance-general] Spectrophotometer use and material reflectance

Anyone using a spectrophotometer to measure reflectances for use in Radiance? Section 5.1.9 (p304-307) of the Radiance book shows how it can be done. Is this method still used, and if so could you post/ email the scripts spct2xyz.csh and xyz2rgb.csh?

Any tips/pointers not already covered in Section 5.1.9 would be much appreciated. We'll be using a Konica/Minolta CM-2600d portable spectrophotometer.

Cheers,

-John

-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)

[email protected]
http://www.iesd.dmu.ac.uk/~jm

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

Hi Iebele,
Many thanks for the help and scripts -- much appreciated. We'll try it out next week.
All the best,
-John

···

-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)

[email protected]
http://www.iesd.dmu.ac.uk/~jm