Suitable software and spectral data

[Prepper]

I was just going back thru the G7 How-to again and came across the following paragraph and wondered if someone here could explain this a little more for me? What is suitable software and what is spectral data?

The reason I'm asking is I would be interested in eliminating metamerism, as referred to here, as much as possible because we only have one light booth, at the press, and none in the creatives or prepress areas and we see a pretty big difference in proofs in those areas which disappear in the correct lighting but see no possibility yet of getting more correct lighting in those other rooms? Could this possibly help with getting the creative and prepress proofs to match closer under non-standard viewing conditions? We create and print all our own work here in-house.

Thanks for any input,
Terry


"9.7 Measure characterization data
Measure characterization data from each of the selected sheets with a spectrophotometer, then build an ICC press profile from the averaged data. If possible, save the original measurement data in spectral format rather than CIELab(D50). With suitable software and spectral data measured from a specific light source, spectral characterization data can yield an improved ICC profile that reduces the metameric problems caused by non-standard viewing conditions, or variations between standard light sources."

 

[meddington]

I was just going back thru the G7 How-to again and came across the following paragraph and wondered if someone here could explain this a little more for me? What is suitable software and what is spectral data?

Spectral data is referring to that derived from a spectrphotometer reported as reflectance per wavelength of light within the visible spetrum (380-730 nanometers or thereabouts). This is what spectrophotometers measure prior to delivering Lab valules (which are derived by multiplying the spectral data, the illuminant data and the color matching functions of the standard observer).

Suitable software would be a profilemaking package that allows the user to change the illuminant when creating the profile. ProfileMaker has this ability, Monaco Profiler does not for example. With this ability, a user can select an illuminant other than D50, or possily use data from measuring their own light, to alter the calculation of the Lab values in the PCS. This would be useful if you use non-standard lighting primarily for viewing proofs.

Now, whether this will help with your problem is another story. Are you saying that the proof and press sheet looks similar under D50 lighting, but dissimilar under non-standard lighting? creating a profile using the non-standard lighting might possibly shift the problem back to the pressroom, and further, its been my experience that the press inks are more "metameric" than the proof, so that the issue could still exist anyway.

If you have "suitable" software you could certainly test out changing the illuminant upon profile creation, but I would suggest that it would be much simpler and less frustrating, not too mention better overall, to create standard lighting conditions for the departments that this would be deemed important.

 

[juergenroesch]

Terry,

as Mike points out you could measure the lighting in your design studio spectrally and load this as illuminant data to get a simulation profile calculated which then should give in your design area a decent visual representation.

You likely already can see the flaw: this also requires that the lighting in your design studio or wherever this particular profile is used is consistent with the lighting you measured when building that profile. Sun or fog outside a window can have a huge impact and most likely worst are colored blinds.

It doesn't help. For color accurate design workplaces you have to have slightly subdued lighting and also no aggressive colors surrounding the workspace. Even woodcolored tables can be critical. Monitors should not be glossy and workers should not wear bright or intense colored shirts as all these can tire the eyes and take away some ability to do accurate color judgements.

For good lighting check out the offerings of for example Graphic Technology INC. where you'd not only be able to get desktop viewers, but also recessed ceiling lights which are as accurate as the viewing booth on your press.
If you want to see what disastrous effects different light conditions have on the perception of color, check out the CRD-1. In my opinion the best tool to educate retouchers and customers

Juergen

 

[Lukas Engqvist]

Talking of tiring the eyes has anyone seen a graph on how tiredness affects colur vision? How long can a prepress worker correct colour before tiredness gives bad judgement? I know if I spend a marathon session fixing pictures, seeing the same pictures after a day or two I can do a better job at doing last minute adjustments, the wonder of adjustment layers