Looking for construction information on a colorimeter

[Norm Dresner]

For both of my hobbies -- photography and model building -- I'm often
concerned with color matching between various things. A professional
Colorimeter is typically an expensive piece of equipment, but with extensive
knowledge of optics and electronics I don't think that constructing one
would be beyond my skill levels. Does anyone know of any web sites or
magazine articles which give information that would be useful in designing
or building one "at home"?

TIA
Norm

 

[Dave]

For both of my hobbies -- photography and model building -- I'm often
concerned with color matching between various things. A professional
Colorimeter is typically an expensive piece of equipment, but with
extensive knowledge of optics and electronics I don't think that
constructing one would be beyond my skill levels. Does anyone know
of any web sites or magazine articles which give information that
would be useful in designing or building one "at home"?

TIA
Norm

I've been round this loop for a client. You can get cheapish colour sensors,
for instance the TAOS TCS230. The problem turns out to be determining the
response of the filters in those sensors - they tend to overlap somewhat,
and also there are typically IR leaks to deal with. It is easy to get
numbers, but somewhat harder to relate them to what you can see ...

If I do it again I'll use a broad band sensor (TAOS TSLxx) and spend some
money on precision colour filters.

Dave

 

[Rich Grise]

For both of my hobbies -- photography and model building -- I'm often
concerned with color matching between various things. A professional
Colorimeter is typically an expensive piece of equipment, but with extensive
knowledge of optics and electronics I don't think that constructing one
would be beyond my skill levels. Does anyone know of any web sites or
magazine articles which give information that would be useful in designing
or building one "at home"?

If you just want to know what color something is, could you take a picture
of it with a digital camera and look at the R,G,B values of individual
pixels? (like, with a paint program)

Good Luck!
Rich

 

[Spehro Pefhany]

For both of my hobbies -- photography and model building -- I'm often
concerned with color matching between various things. A professional
Colorimeter is typically an expensive piece of equipment, but with extensive
knowledge of optics and electronics I don't think that constructing one
would be beyond my skill levels. Does anyone know of any web sites or
magazine articles which give information that would be useful in designing
or building one "at home"?

TIA
Norm

Ages ago there was a project in Nuts and Volts that used several
colored LEDs and measured the reflected light from the surface using
an unfiltered sensor.

 

[spinning]

Have a look at this:

http://sci-toys.com/scitoys/scitoys/light/cd_spectroscope/spectroscope.html

 

[Norm Dresner]

| On Fri, 03 Mar 2006 18:15:25 +0000, Norm Dresner wrote:
|
| > For both of my hobbies -- photography and model building -- I'm often
| > concerned with color matching between various things. A professional
| > Colorimeter is typically an expensive piece of equipment, but with
extensive
| > knowledge of optics and electronics I don't think that constructing one
| > would be beyond my skill levels. Does anyone know of any web sites or
| > magazine articles which give information that would be useful in
designing
| > or building one "at home"?
|
| If you just want to know what color something is, could you take a picture
| of it with a digital camera and look at the R,G,B values of individual
| pixels? (like, with a paint program)
|
| Good Luck!
| Rich

Been there -- done that. Also used a scanner. Imported the output of both
into Photoshop and sampled colors that way. It works but it stinks as a
workable procedure.

Norm

 

[Norm Dresner]

| Have a look at this:
|
|
http://sci-toys.com/scitoys/scitoys/light/cd_spectroscope/spectroscope.html

Yeah -- they used an old CD as a diffraction grating. I've thought of doing
the same thing with some surplus prisms I have. Just add some optics to
spread out the output light and a measuring instrument. It may yet happen
that way.

Norm

 

[Rich Webb]

For both of my hobbies -- photography and model building -- I'm often
concerned with color matching between various things. A professional
Colorimeter is typically an expensive piece of equipment, but with extensive
knowledge of optics and electronics I don't think that constructing one
would be beyond my skill levels. Does anyone know of any web sites or
magazine articles which give information that would be useful in designing
or building one "at home"?

Maybe this guy (COTS product, not a design/build)
<http://www.pantone.com/products/pro...Area=8&idProduct=151&idArticleType_Products=0>

I belive it works by sampling the reflections from a sequence of
differently colored LEDs. Shouldn't be unreasonably hard to do with
LEDs of defined spectra and sensors (photo-transistors?) of defined
sensitivity. Calibrating it might be tough if you wanted absolute
measurements (use white/gray/black targets?) but used for color
matching it should be do-able.

 

[Norm Dresner]

|
| >For both of my hobbies -- photography and model building -- I'm often
| >concerned with color matching between various things. A professional
| >Colorimeter is typically an expensive piece of equipment, but with
extensive
| >knowledge of optics and electronics I don't think that constructing one
| >would be beyond my skill levels. Does anyone know of any web sites or
| >magazine articles which give information that would be useful in
designing
| >or building one "at home"?
|
| Maybe this guy (COTS product, not a design/build)
|
<http://www.pantone.com/products/pro...Area=8&idProduct=151&idArticleType_Products=0>
|
| I belive it works by sampling the reflections from a sequence of
| differently colored LEDs. Shouldn't be unreasonably hard to do with
| LEDs of defined spectra and sensors (photo-transistors?) of defined
| sensitivity. Calibrating it might be tough if you wanted absolute
| measurements (use white/gray/black targets?) but used for color
| matching it should be do-able.
|
| --
| Rich Webb Norfolk, VA

Yeah -- if all I want to do is to color match from physical objects then
yes, calibration isn't really necessary though in the case of using it to
match paint, I'd still need enough calibration to know what color(s) to add
to what I already have to get where I want to be.

Thanks
Norm

 

[Zak]

Yeah -- if all I want to do is to color match from physical objects then
yes, calibration isn't really necessary though in the case of using it to
match paint, I'd still need enough calibration to know what color(s) to add
to what I already have to get where I want to be.

You also need more than RGB to catch 'metamerism' - colors looking
different under different lighting.



Thomas

 

[Norm Dresner]

| Norm Dresner wrote:
|
| > Yeah -- if all I want to do is to color match from physical objects then
| > yes, calibration isn't really necessary though in the case of using it
to
| > match paint, I'd still need enough calibration to know what color(s) to
add
| > to what I already have to get where I want to be.
|
| You also need more than RGB to catch 'metamerism' - colors looking
| different under different lighting.
|

Very true. But how would a commercial colorimeter do it -- if it indeed
does?

Norm