A Curious Thing

I have been having trouble with a printer who cannot seem to match a partular blue I used in the background of a panel. I even gave him the CMYK values: C=72.5, M=72.2, Y=31, k=9 with out clearing up the problem. So I was playing around with the color. I created a patch of that color and then made a duplicate and gave it a pantone color that was close to my original color. The I bought up the color dialog box and set the CMYK values to the same as the original. The two colors did not match! Here are the examples.
I would very much like to hear a someone explain this.
Thanks
J B Lansing

I have been having trouble with a printer who cannot seem to match a partular blue I used in the background of a panel. I even gave him the CMYK values: C=72.5, M=72.2, Y=31, k=9 with out clearing up the problem. So I was playing around with the color. I created a patch of that color and then made a duplicate and gave it a pantone color that was close to my original color. The I bought up the color dialog box and set the CMYK values to the same as the original. The two colors did not match! Here are the examples.
I would very much like to hear a someone explain this.
Thanks
J B Lansing

J B,

color printers are not suited for proofs. A professional printing process is different to what the ink jet printers offer. In addition you would need to calibrate your scanner (film or negative/slide), monitor and printer. The densitometric tools are very expensive - too expensive for 'soho' printing.

And even if you would have calibrated all devices, the colors might differ: the ink cartridges will be from different lots in the factory, and they don't calibrate the inks - there is a relatively large variation in color pigments.

Finally: to proof your colors you need to find a printing company with proof equipment. A letter or A4 size proof costs between US$ 80 and 200, depending on the equipment they use.

Part of the problem is based on the different color models:

your monitor display shows colors that are 'active light', that means the CRT or TFT pixels emit light in the specified color.

A printed color is a passive one - it only reflects the environmental color. Examined in bright sunlight the printed colors will definitely look different than in artificial light in an office or home (bulbs and flourescent lamps emit different wave lenghts - bulbs more read, the 'neons' more blue).

Complicated? You bet!

If you want to achieve a certain color on a specific paper, there is no way around a test pattern. Then you pick the color you want and use that one, no matter how it will look on your screen... a purple on your screen might be the perfect blue on the print!

jens

Where did you get the CMYK values from?

If you used a CYMK swatching system such as TruMatch or Pantone CMYK colors, and your printer (I assume you mean a professional printing company and not a desktop printer) could not match the colors, then the problem is with your printing company. They should be able to reproduce a color if you have specified the color correctly from a reliable swatching product.

Pantone spot colors, are not intended to be printed in CMYK. They are intended to be printed as solid colored, specially mixed inks. Pantone spot color inks are mixed to a special formula and should print the same regardless of who is printing them.

About 1/2 of all Pantone spot colors can be matched using CMYK. About 1/4 of the colors will be close but not match exactly. The other 1/4 are not even close. Deep blues are not easy to reproduce in CMYK. Reflex blue is a good example. There is no way to match this intense deep blue with CMYK.

Finally, as Jens has pointed out, colors you see on the screen are RGB colors and have a much greater gammut than CMYK colors. So many beautiful colors you can create on the screen are just not in the gammut of CMYK printing.

This is why Xara, and most graphics software, offers a Simulated CMYK color space (Window > Show Printer Colors). In this color space, the usually vibrant screen colors appear dull and muted. But in reality, these colors are closer to what the printed output will be.

Hope this helps answer your question.

Gary

This may sound grumpy and I don't mean it to be. But, while you both gave me very good information, it does not answer the question. Why do the two samples shown look different when they have the same CMYK values?
The one on the left looks significantly less saturated than the one on the right. If I look at their RGB or HSV values they ARE significantly different. It seems to indicate that CMYK does not provide a complete definition of a color. Incidently I did finally supply the printer with a PMS color number that he matched.

Hi J B Lansing,

Gary's information about the simulated printer colors is the key to the answer. The attached image shows the same variance in 'brightness' as your first post.

You don't sound grumpy at all. Getting accurate color is a very frustrating thing. And it has been from the day we started trying to get color from the computer to print like what we see on the screen.

CMYK color is not intended to be viewed on the screen. CMYK color is one color model and RGB is a very different color model. If you look at an image printed in CMYK on a sheet of white paper, and then look at the same image on a color corrected light box on a 4 x 5 or 8 x 10 transparency, the transparency will look much brighter and the colors will appear more vibrant. There is no way you can capture the same vibrancy in CMYK printing.

Red is a very good example.

Several years ago, I worked on a printing project with a professional photographer who had taken a spectacular studio photograph of a red sports car. The 8 x 10 transparency was rich and saturated on the light box. And yet the printed version of the image was dull and the colors were muted.

We finally used a "touch plate", a 5th color, Rubine Red which we ran along side the magenta which made the printed red almost as rich and bright as the transparency.

Hexachrome printing, which adds an orange and green to the CMYK is capable of producing more vibrant and saturated colors. CMYK is just limited by the bandwidth of colors it is able to accurately reproduce.

Gary

From reading this thread, it seems JB's question still isn't directly answered. Is it possible for what appear to be two different colours to have identical CMYK values??

Regards, Ross

PS - thanks Jens & Gary. Your explanations on this complicated subject are very educational.

What Color Really Is....

Don’t forget folks, color requires:
1) A light source
2) A reflecting or transmitting object
3) A beholder - eye, phototube, diffraction instrument, etc.

CMYK only affects #2; and, theoretically if two colors have the same CMYK values they will look the same to one person under the same light source.

Unfortunately, I don’t think any printer on earth can print the same color twice. AND, If I’m dissing your pantone swatches or color calibration equipment, hey, go visit a large print shop. They put trees in one side of the building, and with pressmen running up and down the line slapping gallons of ink on the press, colored brochures come out the other end - neatly folded.

Rgds,
tad

Soquili,
The color shift in my example is not due to a change in the display. What you see is exactly what is displayed. I believe it is a coincidence that it looks like your example. The point is that it seems CMYK is not a complete definition of a color. While I recognize that different color media and different color standards (not the right term, I mean RGB vs CMYK) can result in color shifts, This example is displayed in a common standard.
I did not use trickory to arrive at these colors, they occured following the procedure I outlined. Try it and see if you get the same result.
J B

Hi J B Lansing,

This is getting more and more curious. I saved your image from above and imported it into XaraX1 1.1b and tried to use the colour sampler (eye dropper) to get the colour value for the left side. Holding the left mouse button down, I could see the rectangle I had selected change to the correct visual color. Releasing the button the color changed to that of the right side of your image. I downloaded the 1.1d patch and tried the same test and got the same result.

I then imported your image into XaraX 1.0d and used the eye dropper on the left side of your image and got the correct visual colour and when I released the mouse button it remained that colour. The CMYK values were not the same as you mentioned. C 68.2% M 68.2% Y 48.6% K 0%. I then opened your image in PhotoShop 7.0 and sampled the left side of your image and got the CMYK values C 78% M 75% Y 23% K 7%.

There was an obvious bug in the XaraX 1.1b and 1.1d colour picker, because the sampled colour was changed upon releasing the mouse button. I expected a difference in CMYK values between Xara and PhotoShop due to their different methods of handling colour space, but not as much as I saw.

Hi Soquili,
I am begining to think there is a bug in XaraX1 Try this. Start with a square, and color it using the HSV tool. Make the color a subtle one with some gray tone. Make a copy of the first square and give the second a pantone color from the color dropdown that is close to the original color. Switch to the CMYK color tool and make the second square the same CMYK values as the first square. Do the colors look the same?
For me, sometimes they do and sometimes they don't. Most curious.
J B

Here is the XartaX1d File
J B

I tried matching colours as you described, but could not get a match. I tried using the colour picker on your .xar file the same as I did with the jpg file. I got the same results. The colour picker has the correct colour until I release the mouse button.

I also found that I can not open your XaraX1 1.1d file in XaraX 1.0d. I saved a file from XaraX1 1.1d and could not open it in XaraX 1.0d. I get an "Internal Program error" message, the error number is 608 followed by a random number of characters. The characters to the right of the decimal point are different each time I try to open the file.

Hmmmm... I can open the file by clicking on it. I'm using Window XP and Xara 1.1d if that makes any diference. could someone else try opening the Xara file. Thanks
J B

Soquili,
I tried the color picker and got that same results you did; a jump in color when I release the button. Are there any Xara representatives reading this? Any comments? Help?
J B Lansing

J B Lansing,
i used your posted xara file and drew 2 rectangles and used the color picker to fill each one. the colors apeared to match the 2 colors but the hsv and rgb values were different from yours but they apeared to match on screen visually. if that makes any sense.

The file opens fine in XaraX1 1.1d, but causes and error when I try to open it in XaraX 1.0d as do any files I create with XaraX1 1.1d. Before I installed the 1.1d patch, XaraX 1.0d would open files created with XaraX1 1.1b.

i would image there is something corrupt in JB file. The file opens okay in version 1.1 (8 jun) but crashes in x, with same 608 error. You should get and error message when opening a 1.1 file with 1.0, but it does still open. This crashes the window, but not the program.

J B, there's no bug and no problem at all.
Result of analising your xar file:
1. left rectangle local fill color is stored as HSV
2. right rectangle local fill color is stored as CMYK

When your color editor is in CMYK mode and you select HSV/RGB object, then CMYK values are generated 'on the fly'. Since there is no way to adequatly convert all colors from RGB/HSV to CMYK, you get not the values that you see.
Hint: re-enter any CMYK value for left object and it will become the samelooking as right one. Why? Because it's converted to CMYK and rendered with those CMYK values.
Another hint: change nothing just switch color editor to HSV mode and select left then right shape. You see? Colors are NOT the same! And that's what you see.

Another thing with color picker.
Color picker converts color from screen to current color model of color editor. If you color editor model is RGB/HSV - no problem. If it's CMYK, picker converts picked color the same way as it did with representation of other color models.
So, if you are picking color from HSV/RGB to CMYK it will be the same as you see in color CMYK editor for that object. But if you pick color from CMYK to CMYK color is twice converted: first - it's converted from original CMYK to RGB to display, then it's converted from screen RGB to CMYK but this conversion is not adequate. So you may get different CMYK values than of original object, and so it may look different.
Also don't forget: different CMYK values results to same color in RGB color space and vice versa - one RGB color may be represented as multiple different CMYK colors.

P.S. Due to CMS features, RGB and CMYK colors are separated (converted) to CMYK differently. That's why you should not include overlaping or same looking objects with different color models.
Simply stick to RGB/HSV or CMYK. Preferably to RGB - then you'll have no need to consider difference between what you see and what you'll get. Use CMYK only if you know exactly CMYK values of what you want to get, and not rely on what you see on screen.

Hi covoxer,
It is becoming clear. What I think you are saying is that when you change from say HSV to CMYK you are doing more than just changing the way the colors are represented. You are at least potentually changing the color itself? I got myself in trouble because I started out using HSV model (it seems the most intuative) and then tried to represent the color as a CMYK value which is only an approximation. What I have been doing is to complete a rendering using HSV colors, Exporting as a Tiff and then using Corel Photo Paint to convert the results to CMYK for printing. All this seemed to work. But.... I just need to change the way I setup my colors initially. The light dawns http://www.talkgraphics.com/images/smilies/smile.gif http://www.talkgraphics.com/images/smilies/smile.gif
J B Lansing

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by J B Lansing:
...when you change from say HSV to CMYK you are doing more than just changing the way the colors are represented. <HR></BLOCKQUOTE>
Yes you've got it right!
Now details.
XaraX stores every color in one of the three models: RGB, HSV or CMYK.
You can see in which model color is in color galery. Open color galery, press 'Options.../Properties...', select 'Display full information'.
Now you see values for every color in galery. They are represented in RGB, HSV, CMYK models.
Clear? Ok.
So how does Xara render those colors on screen and during color separations?
Everything you see on screen is RGB. So if color is stored as RGB you see it without conversion. In case of CMYK, color is converted to RGB then displayed so you see some kind of closest maching color from RGB color space.
When doing color separations CMYK coloros are separated just as they are stored, and RGB are converted to CMYK according to CMS.
As a result, 2 colors represented in 2 different color models may look not the same both on screen and after color separations.
Color picker allways takes screen color which is RGB and separates it to CMYK if color editor mode is CMYK. Color editor does the same when shows you CMYK values for RGB color.
As to HSV, it's adequately equivalent to RGB. It means that color conversions between those two color models are loseless.

Thanks covoxer,
I can understand your explaination because it is given from the program perspective. I mean you have discribed what XaraX does not just some detatched concepts. This really helped.
J B Lansing