by Mike McNamee Published 01/06/2007
At Professional Imagemaker we always examine a paper in a special uv-booth as well as looking at the Spectral Power Distribution (SPD). The SPD is a fancy term for how the reflectance of a paper varies in different colours (wavelengths) of light. By looking at the SPD we can measure the lift of reflectance in the blue part of the spectrum over the base level for the rest of the spectrum. We also examine both the front and the back of the paper in the uv-booth. Any fluorescence on the back indicates that the OBA is contained in the body of the material. For high-value rag papers, the waste, trimmings and off-cuts are often recycled so that the coating seems to end up in the mix (good for the planet though!).
In the diagram, the high lift of Torchon is very evident. Photo Rag has a barely detectable lift, but the Museum Etching is hugely depressed at the 440nm wavelength. Photo Rag contains OBAs the body of the paper only.
Photo Rag 188, 308, 460 PhotoLine
Photo Rag is the material with which we are most familiar having made dozens (or even hundreds) of profiles over the years. It is the benchmark material that we use when reviewing printers. The material is available as 188, 308 and 460gsm weights and a number of other options that we will list and characterise separately. One profile will usually suffice for all the plain 'Photo Rags' including the double-sided Duo. When the coating differs (eg Silk, Pearl or Satin), a different profile would be in order, although differences might be marginal. The audit print obtained using the Hahnemuhle profile had an average error of 7.4 LabΔE/4.0ΔE2000, reasonably typical for Epson K3 on a Photo Rag. We found that the use of VFA as the media setting was more neutral than WCRW as with the ArtLine series. Bespoke profiling of the Duo variant (see next media) reduced this error to 5.5LabΔE/3.26ΔE2000 which is again typical of the results we obtain.
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