Color separation techniques when printing dark fabrics

At present, many small screen-printing companies are using T-shirt screen printing, but you can inquire about them. Most of them are only printed in light colors and dark in printed ones. Because of the same fabric of different colors, the same method can not print the same satisfactory results. The pattern printed on the dark fabric is noticeably dark, which greatly reduces the design effect. Obviously not satisfactory.

To change this phenomenon, the key is not in the printing process, but in the pre-press film production. At present, some screen printing units apply a layer of white background on dark fabrics, and at the same time give up four-color inks and use spot-color inks. In this way, the effect of printed fabrics is greatly improved. But where are the white background films and spot color films? This article uses Photoshop 7.0 as an example to briefly describe this technique.

1, check and analyze the original

After getting the printed manuscript, first check whether its size and resolution can meet the customer's requirements. Second, check if the color model is RGB or CMYK. It is worth noting that although the manuscript for printing requires the CMYK format, before the color separation at this time, the customer must be provided with the RGB manuscript. Otherwise, the manuscript has lost a lot of information during conversion to the CMYK format. Finally check the background color of the original. That is, the original background color should be the same as the color of the printed fabric. If it is different, you need to make corresponding changes. In this case, the background color is black.

After the inspection, it is not busy with color separation, first analyze the original. Is it biased towards some real-color graphics, or is it focused on images with tonal adjustments? Obviously, this example belongs to the latter. In addition, the analysis of the manuscript mainly consists of what color, which means to do a few spot color version, as well as the use of which kind of spot colors; all know what counts and then proceed to the next step.

2, system white plate

Copy the original image (Image → Copy), convert the copied new file to a grayscale format (Image → Mode → Grayscale), and invert (Image → Adjustment → Invert). At the same time, open the curve panel (Image → Adjustment → Curve) and adjust the curve with the mouse. You can try to move the mouse to observe the effect. The goal is not to lose unnecessary subtle levels. It is usually 1/3.

3, making spot color version

First, use the color selection tool to select a main color of the image, open the color range panel (selection → color range), or open the color range panel first, then use the color selection tool on the panel to select the main color of the image, adjust the color tolerance , To achieve the best level, the so-called best, refers to the scope of the color are included, which requires a lot of staff experience.

After adjusting, click OK and a selection will appear. To save a selection (Select → Save Selection), a new channel is automatically generated. After the selection is deselected, the channel is inverted.

In the channel panel, select the RGB channel, use the color selection tool to select the main tone you think is best, and note the R, G, B values. Select the newly created channel, click the arrow in the upper right corner of the channel panel, and click the channel option in the drop-down menu. Change the R, G, and B values ​​of the channel color to the R, G, and B values ​​you just recorded. A spot color screen is ready.

Next, select the second and only the next dominant color, and use the same method to make the second spot color version.

4, making high-gloss and shaded version

Select the color of the highlight part of the image and the color of the shadow, and make two spot color versions. The method is the same as step 3. At this point in the observation channel panel, except for the three channels R, G, and B, there are already four more channels.

5, the screen soft proofing

Select RGB channel to clear the image. Set the channel to the color of the printing fabric (black in this case). Click on the arrow in the upper left corner. In the channel drop-down menu, click on the new channel to create a new channel.

Next, open the file created in step 2, select all, and copy. Go back to the file channel you are working with and paste it. At the same time, the color of the channel is set to white, that is, the R, G, and B values ​​are 255, 255, and 255.

At this point, all the channels are turned on, that is, all the channels are visible, and the simulated printing effect on the screen can be seen.

Of course, this effect may also be unsatisfactory, then you have to choose a spot color again, and then follow the steps to remake the spot color version. If you are professional enough, you can use Photoshop's powerful features to make fine adjustments to each channel. The effect will be better.

6. Concluding remarks

The next job is to make a color separation sheet based on these channels and then print it. However, it should be emphasized that during the entire color separation process, when selecting each spot color, it is necessary to consider whether the printing unit can deploy the spot color. Although this separation technique can solve the problem of dark images printed on dark fabrics, if there is a clear deviation in any of the spot colors, it will affect the final results. In addition, in the whole process, there are many places where adjustment parameters are based on the staff's experience, and all of them work well.

Source: Screen Printing