Matching Paint RGB Values

[Anonymous]

Dulux paints in Australia now give RGB values for all their colours. This is extremely useful to get the exact colour and see what it looks like on buildings.

Please go to http://www.dulux.com.au/html/specifier/colour_atlas.aspx select a colour and double click. It gives the RGB values as well as other technical information. I have tested in ArchiCAD and it gives the exact colour.

Now we just have to get the light right on the colours to get a clear impression.

Regards,

[Dwight]

I only waded into this discussion to dash the naive and false hope that simply having the RGB value results in accurate color.
There's plenty of work to do after that or tears will result.

[Djordje]

Graeme wrote:
I cant find the RAL Add On since ArchiCAD 9? The Goodies folder is no longer in the AC11 folder. Has it been placed elsewhere or is it a special Add On from elsewhere?

Check Goodies in your Help ...

[Anonymous]

Djordje,

Thanks for that info but can you be more specific please. I can't find RAL Add On in the Goodies folder in the Help menu. There is Profiler, Accessories, etc but I cannot find RAL.

Reflectance Values

The Resene and Dulux sites give Light Reflectance Values for paint colours but I am not sure how they relate to Ambient, Diffuse, Specular, and Mirror in Archicad? The paint websites only give one LRV as shown in the following excerpt from the Resene site. Any ideas? Thanks.

[Ralph Wessel]

Dwight wrote:
I only waded into this discussion to dash the naive and false hope that simply having the RGB value results in accurate color.
There's plenty of work to do after that or tears will result.

How true - this is an unbelievably complex subject. I hit the same problems in publishing too. Many printers will only accept colour specs in CMYK because they don't want to be responsible for deciding how they should be converted from RGB - in many cases there is no direct correlation, i.e. there is no CMYK equivalent to a specific RGB value.

[Dwight]

Observing that printing ink defined in CMYK cannot represent as many colors as light rays defined in RGB can is correct and a concern to offset printing houses accustomed to the outrageous requirements of advertising agencies attempting to match a difficult Pantone spot color. After that, the quiet reason of architects merely wishing to define 1000 different greys is simple.

MY angle on this is that accuracy or inaccuracy aside, having the RGB is just the start of defining a material. Take paint, for example. You want to show paint on your surfaces, and those surfaces will be sprayed, brushed or rolled, the paint will be eggshell, glossy or semi-glossy, it will have surfactants that automatically level it or not.

These qualities affect the observed color because the unpublished values - how the paint surface reflects light - TOTALLY destroys the usefulness of and false confidence provided by the manufacturer's RGB. If you have to guess at the diffuse, ambient and specular reflectivity of the surface, you might as well just guess at the RGB, too.

And DON'T get me started on metamerism or I will have to tell the story of visiting a light test room of a Mexican car seat manufacturer watching a team compare light falling on an expanded vinyl seat side versus its leather seating surface as seen at sunset when a driver opens his door and sees that the two don't match like they did at noon. He then goes angrily back to the dealership to learn that even though the leather interior on his Explorer cost an extra $1800. it was only the actual parts of the seat he sits against that were cowhide [more-or-less, seeing as how your cheaper cars only have acrylic-impregnated hide costing only slightly more than vinyl or fabric and not properly tanned leather like in your Bentley] and the rest was lousy, ordinary vinyl.

This, already, after the outraged owner, being from New Mexico and him having worn a new fringed buckskin jacket and the ochre dye from the buckskin fringes transferring to the beige seat back from being ground repeatedly against that seat back by his broad, manly shoulders and Ford already rolling over once and replacing the seat under warranty.

You can't blame that on metamerism.