Introduction: Before you Begin
If you didn’t separate your colors into layers while you made the piece, you have a few options:
- Option 1: Separate out the colors using the Menu > Select > Color Range (try a few different tolerances) and make spot channels with that.
- Option 2: Convert the whole image to Grayscale, and re-color the whole image using the multi-channel color space.
- Option 3: Simulate a four-color process print (CMYK) by using the channels as they are.
A few things to check before beginning color separations:
Adjusting your document set up:
- Check your image size.
- The maximum printable area is 16” x 10″.
- This allows room for crop and registration marks.
- Set your resolution to 600 dpi.
- Menu Bar > Image > Image Size > Resolution: 600
- Set your color space to Adobe RGB (1998).
- Menu Bar > Edit > Convert to Profile > Destination Space: Adobe RGB (1998)
- Download the IC Riso swatches (there is a link below)
- If you prefer to add the Riso colors manually, be sure to add them as SPOT PANTONE colors
- Save your document as a new file.
- Note: these methods all require switching your color mode and deleting channels, which can be a destructive workflow (e.g., layers get flattened or color information is discarded). When working with channels, it is difficult to revert back to the previous look. It is best to keep your final piece, with all its layers and edits, as a separate file.
Imaging Center Ink Colors – Fall 2020
The IC currently has 10 colors of ink in stock. The IC will allow up to 4 colors per Riso print submission.
Risograph ink is translucent, so its final appearance depends on the color of the paper it is printed on and then the layering of each ink color.
Colors can be overprinted to create new ones. It is possible to blend any combination of tints together to produce color variants.
Download the Imaging Center Fall 2020 color swatches HERE
Channels & Color Systems Overview
Understanding RGB vs. CMYK vs. CMY
The primary colors of light RGB (Red, Green and Blue), represent a visual range that, in theory, can produce any color that can be seen by the human eye. Mixing with light is an additive process. (When you add all the colors together, they make white.)
Printing is a subtractive color process, and uses the opposite colors, CMY (Cyan, Magenta and Yellow) to mix and produce an image. Working with physical colors (i.e. dyes, pigments, inks) brings with it the limitations of your materials. In theory, cyan, magenta and yellow, all together should produce black. But in reality, the pigment usually turns to a muddy, inconsistent brownish-black. (The shade of brownish-black is dependent on your materials.)
This is why Black (or K for Key) is added in addition to the CMY gray-blend, giving you a sharper, richer, darker black.
So, when you are printing in CMYK, about half of your grays and blacks are made with an even blend of CMY, and the other half are a layer of black printed on top. In theory, all of your CMY channels should have the same information as your black channels, just at a lighter value.
Overall, subtractive color spaces tend to have a wider spectrum of colors to offer. This is why most people work in an RGB color space such as Adobe RGB 1998 or ProPhoto RGB, instead of CMYK. Side note: All screens use additive color.
What is a Color System?
A color system is a set of colors that represent a specific visual spectrum.* These few colors are mixed together to create a limited usable range, and that range is called a color system. Examples of a color system include RGB, CMYK and Lab.
* “Appendix A.” Understanding Digital Photography, by Joseph A. Ippolito, Thomson/Delmar Learning, 2003, p. 372.
What is a Channel?
Photoshop organizes your chosen set of colors (e.g. RGB or CMYK) into channels, dividing up your image information by color. For RGB and CMYK, Photoshop also includes a composite channel. Each channel is in grayscale and uses a mask to store each color’s information. You can edit this mask to alter the look of your image and how the channels are mixed.
In RGB and CMYK, you can use the Channel Mixer to change the amount of color information on each channel.
What is a Spot Color?
An additional color that is not a part of an established color system or mode.