Color Conversion (i.e. to CMYK)

When preparing a digital file to print on a commercial press, color conversion is a necessary step.
Usually this involves changing a file from one sort of RGB (i.e. sRGB, Adobe RGB (1998), ColorMatch RGB, etc.) to one sort of CMYK (i.e. SWOP, MP_color_date, etc.).
In all printing, and at some stage in the process, all files will convert to a printing color space (i.e. CYMK or grayscale).
This happens whether your know it (as when printing with us) or not (as when you send an RGB file to a desktop printer).
Below is a snapshot of a method from Adobe Photoshop:

There might be a color-shift when converting from RGB, Pantone, Spot, Lab, Duotone, Tritone, or Index Color to CMYK.
We may require a signed waiver if you submit anything other than CMYK for the front side of your postcard.
The following example illustrates the difference between RGB (red, green, blue - colors that make up light) and CMYK (Cyan, Magenta, Yellow, Black - colors used in 4-color printing):

If you are concerned about color and you have Adobe Photoshop, visit our
Monitor Calibration Info and Printing Profiles to calibrate your monitor to our press.
You can also mail us a color proof and we will determine whether your digital file will match or not (there may be additional costs to adjust your color to match).
How to Check For and Set Color Using:
Photoshop
QuarkXPress
InDesign
Illustrator

How to Set Color Using Photoshop
It is easy to change the color mode to CMYK in Photoshop. Simply go to Image / Mode and pull to CMYK Color.

How to Set Color Using QuarkXPress
In QuarkXPress, there are two areas where you may have non-CMYK color.
One is in your linked images (TIFFs or eps files that are placed into Quark).
The other is in any Quark element such as text, boxes, borders, or lines.
To check for TIFFs you have placed into Quark using the "Get Picture" function, you will need Photoshop.
To check for EPS files placed into Quark, you will need Illustrator .
Check for Quark elements, you will have to select individual elements to see what color they are assigned in the color palette.
In this example, be sure not to use any RGB color swatches.

You may have created a custom Pantone or Spot color.
It is best that you go to Edit > Colors to convert these to CMYK.

Simply click on Model and pull to CMYK.
Any Pantone or Spot color is now converted to their CMYK equivalents.

How to Set Color Using InDesign
In InDesign, there are two areas where you may have non-CMYK color.
One is in your linked images (TIFFs or EPS files that are placed into InDesign).
The other is in any InDesign element such as text, boxes, borders, or lines.
To check for TIFFs you have placed into InDesign using the "Place" function, you will need Photoshop.
To check for EPS files placed into InDesign, you will need Illustrator.
To check for InDesign elements, you will have to select them individually and check the Color Palette.
If the selected element is RGB or LAB, simply change it to CMYK.

How to Set Color Using Illustrator
In Illustrator, there are two areas where you may have non-CMYK color.
One is in your linked or embedded images (TIFFs or EPS files that are placed into Illustrator).
The other is in any Illustrator element such as text, boxes, borders, lines or any other vector art.
To check for images you have placed into Illustrator using the "Place" function, you will need Photoshop.
To be sure that all your vector objects are all CMYK, you will first need to select all (Control-A Windows, Command-A Mac), and then go to Filter > Colors > Convert to CMYK.
To double check that all your vector objects have been converted to CMYK, go to File > Document Info (you may need to select all first) and pull down on the small options menu on the Document Info Palette, to "Options."
In this example all the objects have been successfully converted to CMYK.

Please note that gradients will not convert using the Convert to CMYK Filter.
You should probably create your gradients in a raster editing program like Photoshop and place them into Illustrator.