What Illuminant for a neutral rendering in ColorThinkPro

[tonyrom]

Using an i1Pro 2, I created 3 custom profiles(D50, D65, and A) for Epson Exhibition Fiber. I wanted to compare my profiles to the standard Epson profile to evaluate the neutral rendering ability. CTP uses the Lab.icc as the input profile to the profile being  evaluated against.  I happened to start my testing using the D50 version.  The dE starting at the midtones started to go above 3 and managed to stay below 5.5 to the highlights.  These numbers were comparable to the Epson profile.  I did the same thing for the D65 and A.  The D65 rendering had a blue shift(cooler) and the A had a amber shift(warmer).  This caught me off guard a bit but after thinking about it it made sense.

Can people opine on these two conclusions? 

To evaluate neutral rendering, you must use a D50 illuminant profile.
Since the Epson profile didn't appear to have a color shift due to an illuminant, I concluded the Epson profile was made using D50.

-tony

[Doug Gray]

Using an i1Pro 2, I created 3 custom profiles(D50, D65, and A) for Epson Exhibition Fiber. I wanted to compare my profiles to the standard Epson profile to evaluate the neutral rendering ability. CTP uses the Lab.icc as the input profile to the profile being  evaluated against.  I happened to start my testing using the D50 version.  The dE starting at the midtones started to go above 3 and managed to stay below 5.5 to the highlights.  These numbers were comparable to the Epson profile.  I did the same thing for the D65 and A.  The D65 rendering had a blue shift(cooler) and the A had a amber shift(warmer).  This caught me off guard a bit but after thinking about it it made sense.

Can people opine on these two conclusions? 

To evaluate neutral rendering, you must use a D50 illuminant profile.
Since the Epson profile didn't appear to have a color shift due to an illuminant, I concluded the Epson profile was made using D50.

-tony

For normal use you should select D50. That's what all suppliers of profiles normally do and is what all canned profiles use.

All ICC V2 and V4 profiles are made with reference to D50. What I1Profiler does is let you use different illuminants in creating profiles to adjust the print tables so that the image will look "correct" in the sense that the image will appear as it should after color adaption to whatever the illuminant's white point is. For D65 and D50 there is little difference. For D50 v A there can be small differences in achievable gamut. Particularly in the reds. For any modern printer with multiple neutral inks there should be little to no difference in gray scale rendering with any of the settings.

Making a profile with special illuminants, particularly for fluorescents with low CRIs, can significantly improve color rendering. Choosing an illuminant that matches an industrial grade fluorescent will allow you to produce a print that looks quite good under that illuminant. This can be of use doing a special run of prints for office walls where the illuminant can't be changed and will produce much more attractive prints than one can otherwise do.

[tonyrom]

Thank you, Doug.