How to Create and use Manual Linearization Profiles in Matan PhotoPrint Server

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1 1 Application Note: #011 Date: Nov. 03, 05 Written By: Eitan Abramovich Approved by: Shay Rosenzweig How to Create and use Manual Linearization Profiles in Matan PhotoPrint Server Introduction When printing BMP images with Matan's thermal printing technology, we might have difficulty printing light shadows. The Sprinter can not generate shades from 5% to 15/20%; and dark shadows from 85-95%, depending on the media type. In order to fix this problem we need to RIP images and use Color Management with the PhotoPrint Server. There are two procedures for handling Color Management: Color Correction (by using ICC Profiles) Linearization Profiles (also called Linearization Tables). In order to create ICC Profiles, expensive professional tools are required. The Linearization Profiles can be made in a relatively simple way, either by using measurement tools or manually. The generation of the linearization curve is an important step in printer color characterization. The typical purpose of the linearization curves in conventional four color ink printing is to compensate for dot overlapping and dot size variations and therefore to accommodate the non-linearity of the printing process. In the following sections we will learn how to create and use Manual Linearization Profiles. Note: This document is an elaboration of the Manual Linearization Profiles section in AppNote10 Sprinter Color Management.pdf, describing and explaining the Manual profile creation process in greater detail.

2 2 Creating a Manual Linearization Profile Preparation Before starting, we need to print (without any color management) a CMYK color patch table like the below one (swatches.eps), and examine the results. In most cases, the 5% patch will not appear at all, the patches around % will be print around 5-15%, and patches around 85-95% will be printed around %. This printing test will be used as a reference in the following stages. Creating a manual Linearization Profile After we have located and have examined the problem we can start building the profile. On the PhotoPRINT main menu, select Setup and then Color Profiler. The Color Profiler dialog will open.

3 3 Set the Setup configuration name, Media name, RIP Resolution and the Screen Type and press the OK button. The main Color Profiler dialog will open.

4 4 Click on the Find Ink Limit button. The Find Ink Limit dialog will appear.. These settings are basically for ink printers so do nothing (leave the default dialog settings) and press the OK button. The Not yet done text next to the Find Ink Limit button in the main wizard dialog will be replaced by Done. Next, click the Linearization button to open the Linearization dialog.

5 5 Set the output linearization file name. Set the "Step size" to 5% step or 10% step depending on your CMYK color patches. For a manual Linearization Profile uncheck the Use Densitometer box. Create a new linearization file by clicking New. A successfully generated message will appear. The created Linearization Profile uses a straight linear 45 degrees curve for all the separations and will not influence the print shades at this stage. Click OK.

6 6 Click the Edit button (which is now active) to open the Density Adjustment dialog.

7 7 In this step, you need to adjust the points on the curve according to the actual print output of your patches test table, so that the curve reflects the current output. The software will make the necessary adjustments. This is done either by dragging points on the curve up and down, or by selecting the labels on the X-axis and editing their values in the Output field. It is good practice to start at 5% and work your way up to the 95% point. For example: if you see on your test print that the 25% point prints like 20% - enter a value at the 25% point. One more example: in the printing test you will probably notice that the 5% patch doesn't print at all. This means that you have to push down the curve to the 0% point. However, it is forbidden to enter two identical values. The curve must start at 0% and gradually climb up to 100%. So at this point enter a low value, such as At the second point, (10%) enter the value that is visible on the printing test. Continue to enter the values gradually until the 95% point. Note: The curve should not contain any points that fall below a previous value. If such a point is measured, edit the curve so that the point is above the previous point on the curve. Click Reset to return the curve to its original values. On the Channel drop down menu switch to Magenta and repeat the above procedure. Do the same with Yellow and Black. When finished press the OK button. The curves for each channel will probably not be similar, since each color might behave a bit differently. Press OK twice and exit from the Color Profiler dialog. The new Linearization Profile you just made is ready for use.

8 8 Using and Editing the Linearization Profile Select the SprinterB setup. Select Default Job Properties from the Setup menu. Select the Color Management Tab. Uncheck the Perform color correction check box. From the drop down menu "Linearization table" select the desired profile. Choose "None" for working with no profile. It is possible to import an existing file (as from a previous version) from a different directory by selecting "Add"

9 9 When you create a new profile it is automatically saved in the correct directory and will appear on the drop down list. Press the OK button. RIP the CMYK swatches.eps again but now with the new profile that you just created. Print the file and examine the results. You will probably notice the big improvement in the screen shades values. If the results are not satisfying, edit the profile by opening the Color Profiler dialog again; choose the correct profile and select Edit. RIP the file again, print it out and examine it. Repeat the steps above until you get the most satisfying results.