Written by:
Matthew J. Volpe
Smart Press Production Consultant & National Customer Trainer
Xerox Corporation
Depending on your workflow, you may be asked to make color corrections to a file on press to match a target print. Most press operators immediately create a color curve to change the color of the print, which may not be the best approach. Typically, this takes several revisions of the curve to get the color close to the target. That also means it takes a lot of your time and materials. Here are 3 easy steps to help streamline your color correction process by using Source Color Emulations:
- Know what’s in the file: Run a pre-flight check to see what’s in the file. Is it CMYK, RGB or spot color data? Color curves will affect RGB and CMYK data. However, creating a Tonal Reproductive Curve on FreeFlow Print Server, a Gradient on Creo Print Server and editing an Output Profile on a Fiery Print Server will NOT affect spot colors in Legacy Mode.There are exceptions. Using the Color Wheel/Curves tabs in the Image Viewer of the Fiery Print Server will affect spot colors in Legacy Mode. Plus, color curves will affect spot colors in pdf files when you enable Adobe PDF Print Engine on all 3 color servers mentioned above.
Rely on your CMYK and RGB emulations (Source profiles): Once you know that you are working with RGB and/or CMYK data, you can quickly change color by changing emulations. Emulations will not affect your Spot Colors. Copy (duplicate) the file and submit at least 3 copies of the same file with different CMYK and/or RGB emulations. Check the prints and see which is closest to the target print you need to match.
Each RGB and CMYK emulation change will affect color differently, so get to know the emulations. For instance, if the file contains RGB data, changing sRGB to Adobe RGB will increase the color intensity in your file since the Adobe RGB emulation gamut is much larger than sRGB. Also, remember that changing your Rendering Intents will also have an effect on your color, especially with RGB. Normally, submitting the file with different emulations is a quick way to produce the color you need.
- The very last step, only if needed: Choose the emulation that comes closest to your needs and THEN create a color curve. This will make the curve much easier and faster to create since you are starting out close to the color you want to achieve.
Please ask your Xerox SmartPress Production Consultant for other ideas that can help you streamline your workflow. Why not give this technique a try the next time you are asked to correct color on the press?
why is it a desirable thing for spot colors to be changed when editing curves when using the Adobe engine? I’ve never understood this.
Here is another suggestion you can try along with step 2 above, if you have a Fiery controller/server.
Some files have images that are tagged with their own ICC profiles. This means that the source (or creator) of the image has already provided the intended profile to render the image as intended, and has embedded it along with the image. System 9r2 and System 10 Fiery’s(Xerox 550/560, 700i, 770, 8080, 800/1000, iGen4) have a simple way to use these embedded profiles when they are present.
Open up the color tab in the job properties window, click on the Expert Settings button, and select the Color Input tab. You will see “Use embedded profile when present” for both the CMYK/Grayscale and RGB/Lab areas. Check these boxes and try printing your file again. If any of the images in your document contain profile tags they will be applied and will override the source profiles which are seen in the Basic Settings selection form the color tab. http://digitalprinting.blogs.xerox.com/files/2012/04/embed_prof.png
And one more thing…. to quote the late Steve Jobs:)
Before you make any evaluation of color please ensure that you have followed the DFE recommended calibration/linearization procedure. Make sure you have a stable and repeatable platform to work on.
Great question Aaron, and many thanks to Malcolm for his comments and terrific expertise on Fiery. A spot color via the APPE path is converted to CMYK before it enters the print engine, so the tags that identify a color as a Spot Color are removed. You are now able to affect all colors in the file when using a curve. However, the legacy path honors the tags on Spot Colors.
We have been told recently that to get the best tonal range in photographs, the images must be sRGB not Adobe RGB or CMYK.
Tests on our Xerox1000 confirm this.
Sorry. I’m using a CREO RIP with the latest patches and a Xerox1000 installed August 2010.
You are correct, Kevin. sRGB will give you great results and I would continue using that color path. I compared sRGB to Adobe RGB only to demonstrate the differences between the gamuts and how color can be quickly changed if needed.