D50/2deg vs D65/2deg vs 5k Viewing Booth conditions

[Deleted member 16349]

I may be wrong but I had the impression that in the graphic arts, D50/2deg was the standard for measuring colour. Also a Viewing Booth lighting should be 5K temp. which I thought was related to D50.

Why would a graphic arts customer require D65/2deg measurements? (Delta E of 2.0 cmc 1/1 measured with D65/2deg)

Is there a confilict with the D65/2deg. measurments and with D50/2deg. and the Viewing Booth lighting conditions?

Thanks for any comments.

 

[meddington]

I may be wrong but I had the impression that in the graphic arts, D50/2deg was the standard for measuring colour. Also a Viewing Booth lighting should be 5K temp. which I thought was related to D50.

Why would a graphic arts customer require D65/2deg measurements? (Delta E of 2.0 cmc 1/1 measured with D65/2deg)

Is there a confilict with the D65/2deg. measurments and with D50/2deg. and the Viewing Booth lighting conditions?

Thanks for any comments.

I would guess that the end user is using "D65" viewing conditions (6500 kelvin tubes) and mandating D65/2deg measurements in order to keep things "consistent". Unfortunately this can be a can of worms if D65 is passed all the way back to generation of profiles and color management. Static measurements with handhelds are one thing, but for example, changing the illuminant in ProfileMaker/MeasureTool when exporting CIELab from spectral data is not consistent with handheld measurement.

 

[Lukas Engqvist]

D65 is used by many in photography since it is the blue cast of daylight, also common in low-mid end monitors because they feel the D50 is to yellow.
Remember also AdobeRGB and sRGB are using D65 as white point, and could be why. There is alot of colour management info handed out by consultants who like to calibrate customers monitors and tell them that they can save money by doing the proofs at home. So choosing to calibrate to D65 you can get better nummbers, and get the client to be happy ;P, until they come to the real world

 

[Bill W]

D50/2 vs D65/2

D50/2 vs D65/2

Greetings,

I also have a customer that is asking us to report using D65/2. Mike Eddington and I had a discussion that he posted on the colorsync list a month or so ago about this challenge as our customer is basing their specs, for the most part, on the G7 numbers. As Mike mentioned, an iOne will report numbers different under D65/2 that will a handheld device such as the 528. I also understand that there are no published numbers under G7 for measurement using 65/2 and my customer apparently made a proof that was correct under 50/2 and them measured it under 65/2 to find the "correct" numbers.

In the manual covering my customers requirements, while not stated implicitly, it is implied that one could measure all press pieces using 50/2 to make sure the numbers match the G7 50/2 numbers, switch their device to 65/2, and then report those numbers.

I believe our customer, which may also be Erik's customer, is simulating the lighting in their retail outlets and I have been told that my customer has been using D65/2 for their PMS color QC.

The challenge with my customer is that they want use to use dE equal to or less than 2 under CMC 1:1 tolerancing, along with the G7 tolerances of L = +/-3, a* and b* = +/-2. Unfortunately if my color is at either end of those tolerances the dE is above 2. For instance, using cyan, set L at 52, a* at -35 and b* at -48 and the 1:1 dE is (drum roll and magic number please) 2.97 - ouch.

-Bill-

 

[Deleted member 16349]

I believe our customer, which may also be Erik's customer, is simulating the lighting in their retail outlets and I have been told that my customer has been using D65/2 for their PMS color QC.

The challenge with my customer is that they want use to use dE equal to or less than 2 under CMC 1:1 tolerancing,
-Bill-

Bill,

I am not sure if it is the same customer but the request is very similar and the reason for D65 related to store lighting is similar.

We print with the Dry Offset method on plastic food containers. Due to this, all designs are made with PMS spot colours and not CMY inks. No process printing is done but simulated process printing with multiple spot colours (screens and solids) are used.

Also we normally have no room on the containers for colour bars and therefore we tend to visually match these spot colours to the PMS guide in a controlled viewing booth (5000 Kelvin) . This is not only a problem with the D65 request but in obtaining a dE values since it is usually not possible to measure on the cup.

I am sure some compromise will be found. Usually customers or their prepress agents change their request to account for the realities of Dry Offset container printing, which is new and different to what they are used to.

Thanks to all for the comments. It did help me clarify my view of the potential problems and were used to explain them to our prepress department.

 

[dimitri]

Eric,
You'll get metamerism for sure if you are visually inspecting color under D50 and your customer is inspecting it under D65. Not for all colors, but for a whole bunch of them. I think that there are some light booths that have both light sources available.

I would question the use of 1:1 tolerancing, for DE94 or DEcmc. It allows lightness variation. I do not have a study in my hands, but I think that tolerancing with 2:1 corresponds to human color perception more accurately.

 

[meddington]

I found this article interesting regarding why the printing industry is using D50 and not D65.
http://www.fogra.org/products-en/download/Extra18web.pdf

 

[meddington]

I would question the use of 1:1 tolerancing, for DE94 or DEcmc. It allows lightness variation. I do not have a study in my hands, but I think that tolerancing with 2:1 corresponds to human color perception more accurately.

I think you have the first part backwards. Tolerancing with 2:1 will allow twice as much deviation for lightness as chroma (l:c = 2:1), hence a longer/taller ellipsoid of acceptability along the lightness axis. I do agree that 2:1 corresponds more closlely to human perception however.