Different Purge pages have different RGB values?

[Smile]

I decided to create my own purge pages and got a problem that every purge page I looked as a reference has
slight different color values. Is this done on purpose or what?

MIS Associates Purge 8 http://www.inksupply.com/html/zip/purge.zip

K Lk C Lc M Lm Y

R:0 R:128 R:0 R:128 R:255 R:255 R:255
G:0 G:128 G:255 G:255 G:0 G:128 G:255
B:0 B:128 B:255 B:255 B:255 B:255 B:0

MIS Associates Purge 7 http://www.inksupply.com/html/zip/purge.zip

K Lk C Lc M Lm Y

R:0 R:123 R:0 R:132 R:255 R:255 R:255
G:0 G:123 G:255 G:255 G:0 G:132 G:255
B:0 B:123 B:255 B:255 B:255 B:255 B:0

MWORDS Purge Page 7 http://www.mwords.co.uk/catalog/images/spt/MwordsPurge7.tif

K Lk C Lc M Lm Y

R:0 R:200 R:0 R:0 R:255 R:255 R:255
G:0 G:200 G:200 G:255 G:0 G:178 G:255
B:0 B:200 B:200 B:255 B:255 B:255 B:0

MIS Associates seems to be the right purge pages for me as far as color mixing goes.
Any comments on this?

 

[Grandad35]

I decided to create my own purge pages and got a problem that every purge page I looked as a reference has
slight different color values. Is this done on purpose or what?
Any comments on this?

Welcome to the wonderful world of color management. This isnt an easy subject to understand if you arent REALLY interested, you may want to skip this.

I know that this sounds like a strange question, but what is your definition of Cyan/Magenta/Yellow? A cyan crayon will give a different color than a cyan paint which will in turn give a different color than a cyan ink. For this reason, the SWOP (Specifications for Web Offset Publications - http://swop.org/about/) organization was founded to develop standards for the printing industry so that commercial printers and the people who use them can speak a common color language. Part of these standards includes a US Web Coated (SWOP) v2 ICC profile that contains the minimum color gamut that commercial printers must be able to produce to be certified. In practical terms, this means that if your artwork lies wholly within the SWOP color gamut, it should be able to be faithfully reproduced on any press that meets the SWOP specifications. The benefits of having these standards is obvious.

Using Photoshop, I created color swatches for C/M/Y/K in the SWOP color space (CS), then converted the swatches to 2 different RGB CSs and measured the R/G/B color values in those CSs:

sRGB (the default CS used on most computer systems)
C 0/174/239
M 236/0/140
Y 255/242/0
K 35/31/32

aRGB (has a larger color gamut than sRGB, and is used by many professionals to better match the larger CS available from todays printers)
C 0/172/236
M 202/0/136
Y 255/242/45
K 39/36/37

A few things to note:
1. Unless your monitor is calibrated, you dont know that what you see on your monitor is what the numbers represent. Even then, you must do a Gamut Warning check (Ctrl-Shift-Y in Photoshop) to see if your monitor can accurately display the color value(s) selected.
2. Black isnt black (but a dark gray). Commercial printers (and inkjets) cant achieve a true black, even with a separate black ink the C/M/Y only inkjets wont do as well as this.
3. Yellow is close to Red+Green in the sRGB CS.
4. Magenta (Red+Blue) is too saturated in the reds and blues for most printers, so the blue must be lowered to give a color that can actually be printed.
5. Cyan (Green+Blue) is too saturated in the greens for most printers, so the green must be lowered to give a color that can actually be printed.
6. There ARE colors in between the C/M/Y/K colors where the printer can generate colors that cant be represented by most R/G/B monitors.
7. The R/G/B color values depend on the CS that they are defined in.

Just for information, my calibrated monitor can accurately display the SWOP C/M/Y/K values, but pure Red or Green or Blue are all outside of its color display range.

In another test, I generated the same C/M/Y/K color swatches, but this time in the CS of my custom printer profile (i9900/BCI-6 Formulabs ink/Costco Paper), then measured the colors in the aRGB CS:
C 0/168/227
M 201/0/137
Y 254/238/49
K 37/36/37
This combination (with 8 inks) doesnt have as quite as large of a color gamut as SWOP (but it is close).

Repeat, starting with Canons profile for the i9900/OEM ink/Canon PPPro Paper:
C 0/173/235
M 203/0/139
Y 255/236/40
K 38/38/49
The OEM ink and paper comes closer to the SWOP color range, but still slightly misses it in the yellows and blacks.

As if all of this wasnt enough to think about, you also have to consider that the inks in your printer arent pure. For example, the cyan ink doesnt give a pure SWOP cyan. The printer almost certainly adds some magenta ink and yellow ink to the cyan ink to generate the cyan specified in the SWOP profile. If your printer uses separate Photo Cyan and Photo Magenta inks (Light Cyan and Light Magenta), there is no way to specify that only these inks be used to print, as this is controlled by the printers internal firmware. Generally, the Photo inks are used exclusively in the lighter tones, then blended with the full strength ink in decreasing percentages as the color darkens, then completely phased out at some (darker) color value.

Long story short there is no purge image that will use only a single ink. There is no single correct set of R/G/B values to generate C/M/Y/K, but the rules like: Cyan = Blue + Green are just too simplistic.

For more reading, try (http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf).

 

[Smile]

I decided to create my own purge pages and got a problem that every purge page I looked as a reference has
slight different color values. Is this done on purpose or what?
Any comments on this?

Welcome to the wonderful world of color management. This isn’t an easy subject to understand – if you aren’t REALLY interested, you may want to skip this.

I know that this sounds like a strange question, but what is your definition of Cyan/Magenta/Yellow? A cyan crayon will give a different color than a cyan paint which will in turn give a different color than a cyan ink. For this reason, the SWOP (Specifications for Web Offset Publications - http://swop.org/about/) organization was founded to develop standards for the printing industry so that commercial printers and the people who use them can speak a common “color language”. Part of these standards includes a “US Web Coated (SWOP) v2” ICC profile that contains the minimum color gamut that commercial printers must be able to produce to be certified. In practical terms, this means that if your artwork lies wholly within the SWOP color gamut, it should be able to be faithfully reproduced on any press that meets the SWOP specifications. The benefits of having these standards is obvious.

Using Photoshop, I created color swatches for C/M/Y/K in the SWOP color space (CS), then converted the swatches to 2 different RGB CSs and measured the R/G/B color values in those CSs:

sRGB (the default CS used on most computer systems)
C 0/174/239
M 236/0/140
Y 255/242/0
K 35/31/32

aRGB (has a larger color gamut than sRGB, and is used by many professionals to better match the larger CS available from today’s printers)
C 0/172/236
M 202/0/136
Y 255/242/45
K 39/36/37

A few things to note:
1. Unless your monitor is calibrated, you don’t know that what you see on your monitor is what the numbers represent. Even then, you must do a “Gamut Warning” check (Ctrl-Shift-Y in Photoshop) to see if your monitor can accurately display the color value(s) selected.
2. Black isn’t black (but a dark gray). Commercial printers (and inkjets) can’t achieve a true black, even with a separate black ink – the C/M/Y only inkjets won’t do as well as this.
3. Yellow is close to “Red+Green” in the sRGB CS.
4. Magenta (Red+Blue) is too saturated in the reds and blues for most printers, so the blue must be lowered to give a color that can actually be printed.
5. Cyan (Green+Blue) is too saturated in the greens for most printers, so the green must be lowered to give a color that can actually be printed.
6. There ARE colors in between the C/M/Y/K colors where the printer can generate colors that can’t be represented by most R/G/B monitors.
7. The R/G/B color values depend on the CS that they are defined in.

Just for information, my calibrated monitor can accurately display the SWOP C/M/Y/K values, but pure Red or Green or Blue are all outside of its color display range.

In another test, I generated the same C/M/Y/K color swatches, but this time in the CS of my custom printer profile (i9900/BCI-6 Formulabs ink/Costco Paper), then measured the colors in the aRGB CS:
C 0/168/227
M 201/0/137
Y 254/238/49
K 37/36/37
This combination (with 8 inks) doesn’t have as quite as large of a color gamut as SWOP (but it is close).

Repeat, starting with Canon’s profile for the i9900/OEM ink/Canon PPPro Paper:
C 0/173/235
M 203/0/139
Y 255/236/40
K 38/38/49
The OEM ink and paper comes closer to the SWOP color range, but still slightly misses it in the yellows and blacks.

As if all of this wasn’t enough to think about, you also have to consider that the inks in your printer aren’t “pure”. For example, the cyan ink doesn’t give a pure SWOP cyan. The printer almost certainly adds some magenta ink and yellow ink to the cyan ink to generate the cyan specified in the SWOP profile. If your printer uses separate Photo Cyan and Photo Magenta inks (Light Cyan and Light Magenta), there is no way to specify that only these inks be used to print, as this is controlled by the printer’s internal firmware. Generally, the “Photo” inks are used exclusively in the lighter tones, then blended with the full strength ink in decreasing percentages as the color darkens, then completely phased out at some (darker) color value.

Long story short – there is no purge image that will use only a single ink. There is no single “correct” set of R/G/B values to generate C/M/Y/K, but the rules like: “Cyan = Blue + Green” are just too simplistic.

For more reading, try (http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf).

Yes thanks for the link, I know that a printer does not use a single ink only to print but these differences are too drastic in MIS and Mwords case.
I even think that different manufacturers like Canon HP or Epson use different values to print Light Cyan or Magenta or any other color and have different ranges when to.

It would be normal if you download a purge page from Canon and it is different than Epson page, the same goes for MIS ink, Inktec all others. It doesn't matter what ink is in the cartridges it is important what printer logic board is programmed to do. Therefore there is no need to be differences in different purge pages if it not said for what printer they are designed, no universal page can be made.

It's just strange how the third party ink companies that sell overpriced cleaning cartridges did not invest any money to actually take a canon 4 color, 6color etc. printer and test those ranges. I should not mention that is extremely hard for a normal user to do because obviously you risk head damage etc.