Wednesday, July 26, 2006, 05:26 PM - Color RelatedSooner or later, every graphic designer finds a beautiful photograph, that their client just falls in love with, and absolutely can't live without. An image so bright and vivid, that it just knocks their socks off; but when the image is converted to CMYK for printing, it ends up looking like a big brown and grey mess. Certain colors just will not ever look the same in CMYK as they do in RGB. But, for all of you lovers of bright, vivid color out there, do not despair, there is hope.
By learning how rendering intent works, you too can make your photos look like they should, reguardless of their CMYK color space.
Let's say that you have an RGB picture that looks like this:
The first step in converting any image to CMYK, is figuring out which colors will be problematic for process printing. In Photoshop, this can be done by checking the gamut warning. (VIEW MENU - GAMUT WARNING) The gamut warning works by analysing your image, and replacing the preview with a "warning color" wherever your image has colors that can not be represented by your destination color space [working CMYK Space,(this is set in the edit menu under color settings)] This shows you which colors will not correctly convert to CMYK.
Here is the gamut warning for our picture.
As you can see by the ammount of grey, this photo contains a lot of colors that will not convert perfectly.
When this happens, the most important thing to understand, to achieve the desired result is how to control the way color management handles the colors that are out of gamut. In most color management systems, the setting for controling colors that are out of range is called "rendering intent".
In Photoshop, the easiest way to control these colors, is to use the "convert to profile" dialog window (under the edit menu in CS2). In this window, you can see the source profile of the image, and set the destination profile. All this is doing, is telling you, which icc color profile is currently assigned to the image, and asking you how the image will be finally output. The "convert to profile" window looks like this:
In this example, my color management working space is set to "North America General Purpose". For almost all commercial printing, choosing the "U.S. Web Coated (SWOP v.2) destination space is a good choice, because, not only is it the default in most current applications, but it is a fairly good CMYK profile.
You will also see the setting for "rendering intent" in this window. This setting will really make the most difference in helping you to convert your images to CMYK, while preserving the colors that are most important.
There are four different settings for rendering intent in Photoshop CS2. Each one has it's own characteristic for converting colors that are out of range to a printable CMYK color.
Perceptual- This rendering intent will change ALL of the colors in your image in an attempt to keep the tonal contrast the same, but change the colors so that everything is in gamut.
Saturation- This rendering intent will move the colors of you image that are out of range to another tone in attempt to preserve the saturation of the tones. While this will might change the tone of your colors, this intent is great for keeping the colors bright and vivid.
Relative colorimetric- This rendering intent WILL ONLY CHANGE THE COLORS THAT ARE OUT OF RANGE, moving them to the closest color that can be reproduced by the output profile (CMYK). This is in my opinion the best default, because it will convert your colors as faithfully as possible, with little or no unnecessary tone change. It does sometimes fall short if your image has a lot of colors out of range.
Absolute colorimetric- This rendering intent, like relative colorimetric, will only change the colors that are out of range, but will desaturate them with no tonal shift, until it creates a color that can be reproduced by the output profile. While extremely accurate tonally, this intent usually leaves the colors looking a little weak and washed out in appearance.
Here is what the image looks like using the saturation intent VS RGB:
As you can see all three conversions to the exact same CMYK profile have different characteristics.
Saturation is great and bright, but some of the colors are not as faithfully reproduced.
Absolute colorimetric seems a little faded, but very faithful tonally.
Relative colorimetric is very faithful tonally, but the colors that are out of range are not quite as bright as the original.
Whenever you are converting a photo with a large number of colors that are out of range, I would recommend simply:
• opening up the "convert to profile" dialog
• click the preview button
• watch the image change as you select different rendering intents.
Once you find the rendering intent that best suites your needs for the image, perform the conversion. By taking this extra step, I think that you will find that you can breathe new life into your final CMYK printed piece.
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Wednesday, July 12, 2006, 04:45 PM - Color RelatedThis doesn’t happen very often but we do have cases in which customers send us a file that has white text set to overprint. Objects or text with white fills or strokes should never be set to over print because there will be no white fills or strokes in that area; the white will disappear on the final piece. Example “A” below has a white fill on the words “Castle Rocks” and prints correctly because overprint was not turned on. Example “B” below is the opposite and should be avoided unless you intend to achieve that affect on your final piece. To avoid the problem on example “B” you should do the following before sending us your final file:
1. Select anything with a white fill or stroke and make sure your overprint for that object is turned off( if you have this option available). In programs such as Adobe Indesign and Illustrator you can select any object(s) and use the “attribute menu” to check and see if your object(s) overprints or not.
2. Turn your overprint preview option on ( if it’s available in your program ) and you will see what objects will be overprinting (refer to examples A and B above). If you want your text to look like example “A” above and your text fill is set to overprint, you might be surprised to find that your white text has disapeared (similar to example “B” from above) when your overprint preview is turned on.
NOTE: In Quark Express, do not create a new white swatch without setting all trapping settings to “Knockout”.
Where is the overprint preview located usually?
To turn the overprint preview on in Adobe Indesign, do this: Go to the “View menu” on the top of your document and choose “Overprint preview”. In Adobe Acrobat professional go to the “Advanced menu” on the top of your document and choose “Overprint preview”. We recomend you download Adobe Acrobat Reader 7.0 from Adobes’ website. To turn the “Overprint preview” on in Adobe Acrobat Reader 7.0, go into Acrobats’ preference menu, and click on “Page Display” on the left side of the menu when the preference menu pops up, and click the “Overprint Preview” option to check it. Next close the “Preference” menu. Your overprint preview in Adobe Acrobat Reader 7.0 should be activated now.
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Wednesday, July 12, 2006, 02:35 PM - Color RelatedWhen asked for a recommendation for a good "royal" blue color, just about every small (1 and 2 color) print shop will point their clients in the direction of Reflex Blue. This is mainly because Reflex is not only a standard Pantone mixing color, but because most neighborhood printers wash up for Reflex Blue runs at least once a week; so the Reflex ink will already be in their presses. This is great for 1 and 2 color printers, because thay can run your Reflex jobs all at the same time. For this reason, many of our clients tell us that they frequently choose a reflex color to standardize their print jobs, and ensure consistancy and repeatibility of their blue colors. Unfortunately for us, reflex is a very touchy color to reproduce consistantly with 4 color process. It is very easy for reflex to tint purple. In fact, If we buy reflex blue pre-mixed from out ink supplier, and run it as a spot color, reflex blue still tends to go purple. The second problem with reflex, is that it just does not want to dry quickly. Whether built out of CMYK, or run as a spot color, reflex probably requires the longest dry time of any color, second only to very rich blacks.
There is an easy way around both of these problems, however. By simply reducing the amount of magenta used to achieve the blue tint, and replacing it with black, a designer can take out "an insurance policy" against both drying issues, and the risk of purple tinting.
Here is my recommendation.
On the left is the standard 4-color build for reflex blue, 100C,75M,0Y,0K. On the right is a great solution, 100C,65M,0Y,10K.
Both of these builds will come out looking about the same on press, but with the build on the right, dry times are reduced, and there is very little, or no chance of it looking purple.
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Friday, June 30, 2006, 03:39 PM - Color RelatedI would strongly recommend always saving your files in CMYK color space for print. The first and foremost reason for this, is that CMYK is a color mode designed to represent the colors of images output using process printing inks. Every output device, (ie: your monitor, desktop printer, a printing press, a television) has what we call a destination color space (the range of colors that can be represented by that device). Most newer versions of professional graphic design software have features integrated for color management. While I could write an entire book on correctly configuring, using and maintaining these features; the actual principal of icc color management is relatively simple- ICC color management is a way to control color, to make images look as close as possible to the way that they are intended, reguardless of the device that they will be output on. That being said, if ICC color management features are used incorrectly, it can be much worse than if they had not been used at all. Another equally important reason to convert your print files to CMYK is GAMUT (the range of colors that can be reproduced by your output device. While CMYK process printing is capable of reproducing a wide range of colors, it can not display every color that can be seen on your monitor. Conversely, your monitor can not display every color that we can reproduce with CMYK printing. When you are designing for print, if you are working in CMYK, you can be sure that all of the colors you see on your monitor can be reproduced at least reasonably well in print.
The image below shows an example of an rgb color that can not be reproduced in CMYK printing.
When this color is converted to CMYK (SWOP v2, relative colormetric), the nearest color looks like this.
This can be very disapointing if you are expecting the first color.
Another common problem seen when files are submitted in RGB color mode, is a profile mismatch. Profile mismatches occur when the incorrect profile is assigned to the file before converting it to a new color space. This can be as easily done as opening the image in a different program, or on a different computer, that has color management configured in a different way.
(I don't expect you to know exactly what I am talking about with the details of the color mismatching in the following examples, I am just trying to demonstrate that things can teribly go wrong)
For example, if a photo should look like this:
But was saved using an SRGB profile, but mismatched to an Adobe 1998 profile before converting to CMYK, it will look like this:
Or was opened up by a program using Pro photoRGB for it's working space, but did not have the correct SRGB profile assigned when importing, it will look like this:
That last one is pretty hard to sell to your customer!!!
To make matters worse, If you remember it or not, when you first installed Photoshop, the program had you pick a setting for your working space. Odds are that you chose either Adobe 1998, or SRGB IEC1966-2.1 (these profiles are totally different!!!) If you forget to assign the profile that you used when saving your file in RGB, you have a 50% chance of your images printing correctly. I don't know about you, but 50% is not good enough odds when I am spending money on a quality print job.
The best way to avoid these problems is to send us your files in CMYK (we use SWOP V2 for our profile calibration because it is the most common, and is assigned by Adobe applications for your CMYK working space; regardless of which default that you choose when installing the program for the first time- Thus 100% chance of successful color.
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Friday, June 30, 2006, 02:15 PM - Color RelatedOne of the questions most asked by customers, is for a recommendation for a gold ink build. While there is now substitution for the real thing. We have through some experimentation, found a build that works pretty well. I would not recommend this for heavy coverage solids, floods, or reverses (if you wand a large gold solid, I would recommend shelling out the money for a 5th color PMS). But if you want some headline text, an icon, or a starburst, etc. to look like gold ink, this build does a good job. In fact after applying an aqueous for scuff resistance; I can hardly tell the difference, in areas of light coverage, between the cmyk and the real thing. Here it is. C-35, M-45, Y-100, K-0 This is closest to PMS 873 on coated paper.
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