Spectral Based ICC Profile

[NathanD]

I am wondering why ICC profiles are generated from Lab measurement files and not Spectral? Does it have to do with software compatibility? Wouldn't a spectral based ICC profile provide added benefit (i.e. reduced metameric issues), since you would be capturing the spectral information of the source?

Nathan

 

[arossetti]

Which software are you using for your profiles? To my knowledge Gateway, Caldera, and Onyx use spectral to build the profile. I would assume i1 Profiler would do the same.

 

[NathanD]

Which software are you using for your profiles? To my knowledge Gateway, Caldera, and Onyx use spectral to build the profile. I would assume i1 Profiler would do the same.

I am able to create either spectral or lab profiles. I am using CoPrA and i1Profiler, both of which have the capability of doing either. I guess I am more specifically asking why common industry practice is lab and the advantages/disadvantages of each.

 

[Deleted member 16349]

I am wondering why ICC profiles are generated from Lab measurement files and not Spectral? Does it have to do with software compatibility? Wouldn't a spectral based ICC profile provide added benefit (i.e. reduced metameric issues), since you would be capturing the spectral information of the source?

Nathan

It is not clear to me what you mean by spectral data in this question. I tend to think of spectral data as being the data that describes the spectral curve over the visual spectrum.

If this is what you mean and you are thinking in terms of matching spectral curves, this is a problem.

One is that printing devices are not capable of matching spectral curves, so one can not make spectral colour matches. The printing processes that are used are based on obtaining metameric matches and not spectral ones. Metameric pairs are the basis of matching colours in printing.

It is possible if a printing process is developed that can match spectral curves with many inks but this might not be so practical and could be quite expensive. Also the amount of data for one colour using Lab or other tristimulus value is very much smaller than the data required to define a spectral curve. So any effort to make spectral matching would be very data intensive.

Lab values are a result of a calculation from XYZ tristimulus values. XYZ values are a calculation obtained from the spectral curve using the xyz functions. One can only make a spectral match by trying to reproduce the spectral curve. Once the curve data has been converted to the XYZ values, the ability to make a spectral match is lost because a metameric pair of spectral curves will be different but the resulting XYZ values will be the same. I suspect that some people are using the term spectral data in a very loose way.

 

[pauly92]

Onyx uses Spectral data for measurement files. But pretty sure only thing it's used for is that onyx allows you to see the curves and if you use .spec files you can change the light source in onyx. Other option is using Colormetric (CIELAB D50) and that won't allow you to change the viewing light source.

You still get the same profile of done correctly.

 

[Kent Chung]

Hello Nathan,

The current ICC version 4 does not support spectral readings inside the tables. With the upcoming iccMax version, there will be spectral based icc profile support as well as many more extra features. You may check them out at www.iccmax.org! You are absolutely correct that spectral readings within icc profiles will provide a lot of extra use cases. Note that the use of iccMax will require new CMMs' support. iccMax compatible CMM will backward support iccV4 and V2, but v2/v4 CMMs won't be able to support many of iccMax's features though.

Kent

 

[arossetti]

Hello Nathan,

The current ICC version 4 does not support spectral readings inside the tables. With the upcoming iccMax version, there will be spectral based icc profile support as well as many more extra features. You may check them out at www.iccmax.org! You are absolutely correct that spectral readings within icc profiles will provide a lot of extra use cases. Note that the use of iccMax will require new CMMs' support. iccMax compatible CMM will backward support iccV4 and V2, but v2/v4 CMMs won't be able to support many of iccMax's features though.

Kent

Interesting; does this mean 1 profile could be used for D50, D65 or any other defined lighting conditions?

 

[Kent Chung]

Interesting; does this mean 1 profile could be used for D50, D65 or any other defined lighting conditions?

Potentially yes. It depends on the way that the RIP is implemented, since the Lab or XYZ values can be calculated from data instead of predefined in the ICC profile.

 

[pauly92]

Interesting; does this mean 1 profile could be used for D50, D65 or any other defined lighting conditions?

1 reading, yes.