Matching swatch to sample.

[Prestohps]

What is the correct lighting and angles to compare a swatch book to a printed sample? What real world methods do you use to assure consistency?

 

[D Ink Man]

What is the correct lighting and angles to compare a swatch book to a printed sample? What real world methods do you use to assure consistency?

I prefer 1 of 2 methods.

1) The sun in the sky is an excellent choice, because it is a common light that is available to everyone on the globe. 'Daylight', oft times referred to as.

2) If you prefer mechanical light, the industry standard has been a 5000 Kelvin light source. Most commercial light booths on the market are equipped with this source, as well as other sources such as UV for example. Coincidentally, this 5000 Kelvin light is most times referred to as 'Daylight' on the control panel of the light boxes.

With that said, I have seen many times that the Sun's light compared to the mechanical 5000 K light can be different. It is a phenomenon that is called metamerism.

Metamerism is the differences seen between colors when comparison, because of the differences in pigments, dyes or other colorstuffs.

It can be a problem when matching digitally created proofs that are made from dyestuffs and trying to match printed inks which are normally made from pigment colorants.

GRACoL 7 however eliminates much of that in the commercial print industry, because the calibrations are done to L*a*b* values initially in pre-press activities and the colors stay constant when printing to a prescribed density.

Hope that helps a bit.

D

 

[gordo]

What is the correct lighting and angles to compare a swatch book to a printed sample? What real world methods do you use to assure consistency?

The correct lighting conditions are covered by ISO 3664. BTW a 5000 Kelvin light source is not sufficient nor does it meet the specification.

What real world methods do you use to assure consistency?

What do you mean? Consistency through the press run? If so, since there will always be variation through the press run, then you need to specify a tolerance. I.e. an acceptable range within which the color can vary and still be acceptable. The most common methods are the use of deltaE as a metric for color variation and solid ink density (for offset). The degree of acceptable variation will either be an industry specification (e.g. ISO 12647-x) or a shop/customer agreed value.

best gordo

 

[Stephen Marsh]

What type of digital printing? Some forms are more stable than others, it will vary on the make/model of equipment and the media.


Stephen Marsh

 

[D Ink Man]

I prefer 1 of 2 methods.

1) The sun in the sky is an excellent choice, because it is a common light that is available to everyone on the globe. 'Daylight', oft times referred to as.

2) If you prefer mechanical light, the industry standard has been a 5000 Kelvin light source. Most commercial light booths on the market are equipped with this source, as well as other sources such as UV for example. Coincidentally, this 5000 Kelvin light is most times referred to as 'Daylight' on the control panel of the light boxes.

With that said, I have seen many times that the Sun's light compared to the mechanical 5000 K light can be different. It is a phenomenon that is called metamerism.

Metamerism is the differences seen between colors when comparison, because of the differences in pigments, dyes or other colorstuffs.

It can be a problem when matching digitally created proofs that are made from dyestuffs and trying to match printed inks which are normally made from pigment colorants.

GRACoL 7 however eliminates much of that in the commercial print industry, because the calibrations are done to L*a*b* values initially in pre-press activities and the colors stay constant when printing to a prescribed density.

Hope that helps a bit.

D

I apologize for my reply.

 

[dleather]

The correct lighting conditions are covered by ISO 3664. BTW a 5000 Kelvin light source is not sufficient nor does it meet the specification.



What do you mean? Consistency through the press run? If so, since there will always be variation through the press run, then you need to specify a tolerance. I.e. an acceptable range within which the color can vary and still be acceptable. The most common methods are the use of deltaE as a metric for color variation and solid ink density (for offset). The degree of acceptable variation will either be an industry specification (e.g. ISO 12647-x) or a shop/customer agreed value.

best gordo

Gordo is right, except he's unclear about ISO 3664. From what I understand ISO 3664 is a standard that includes 5000K temperature lighting (among other things) - it does not replace 5000K lighting. That said, all 5000K lamps are not built the same. You'd be looking specifically for 5000K lamps that try to replicate the D50 range of light, which is closest to the range of sunlight that is ideal for color proofing. Obviously the effects of sunlight change readily, which is why we have bright days, grey days, and marvelous sunsets.

Here's a link to some informative stuff on ISO 3664. I hesitate to send it, as it's a page on the site of a lamp manufacturer. Nonetheless, it's got good info.
link to: What is ISO 3664:2009?

 

[Bob_McC]

Is the swatch something other than ink on paper?

Is the swatch something other than ink on paper?

Gordo is right, except he's unclear about ISO 3664. From what I understand ISO 3664 is a standard that includes 5000K temperature lighting (among other things) - it does not replace 5000K lighting. That said, all 5000K lamps are not built the same. You'd be looking specifically for 5000K lamps that try to replicate the D50 range of light, which is closest to the range of sunlight that is ideal for color proofing. Obviously the effects of sunlight change readily, which is why we have bright days, grey days, and marvelous sunsets.

Here's a link to some informative stuff on ISO 3664. I hesitate to send it, as it's a page on the site of a lamp manufacturer. Nonetheless, it's got good info.
link to: What is ISO 3664:2009?

The responses above are quite correct that there is a lighting environment specified by the graphic arts industry (ISO 3664:2009) that spells out the conditions under which critical visual color comparisons should be made. This standard assumes that you are not comparing significantly different materials (like say fabric versus print or a metallic sample versus a printed samples) so you will not have a problem with metamerism (good color match under one light source, poor match under a different light source).

If you are comparing a swatch that is not ink on paper, then you might benefit by having multiple light sources available ( these are normally a Daylight (D50) source, a store light (CWF), home light (Incandescent) in your viewing environment. The problem is that - if you do see a metameric problem, it would not be easily corrected by adjusting your press settings - it would probably require playing with your ink formulations.

Short answer - place the swatch along side the printed color at the same angle - to avoid any angular color shifts.

Bob

 

[DotBox]

About 15 years ago I was working for an employer who accused me of not matching a swatch as asked. I told him it matched fine at press time, but he didn't believe me...since he was looking at the swatch and a sample from the job in his office. I nervously suggested we go to my press and check it out there, and sure enough it matched quite nicely. He was flabbergasted. We then proceeded to walk around the shop comparing the two items everywhere we went, which included viewing stations designed for color matching. It looked different everywhere we went. We then took it outside in bright sunlight, and we both went "whoa". It looked so far off outside that it was almost hard to believe.

My advice: come to some agreement with the customer regarding proper color match before running the job. Or better yet, send overly finicky customers down the road to your competition, and let them beat themselves up trying to please what could end up being an expensive customer.

Of COURSE there are "industry-wide standards". What there ISN'T is industry-wide implementation OF those standards. Every customer may want something different. Make sure you know what that is before printing the job, and then make sure you give your operator an environment in which he/she has a fighting chance to succeed.