How to Fix Dull or Grey Blacks in DTF Printing

Fix Dull or Grey Blacks | Image Preparation | For LINKO DTF printers | Windows and the English interface of Adobe Photoshop

1. What this document covers

Black areas in the design print grey, not dark enough, or without enough coverage.

One cause is that the black in the image is not pure black. RGB 30/30/30 and RGB 50/50/50 are dark grey, not pure black, and the difference is hard to see on screen. In testing, pure black and these dark greys printed on the same fabric were clearly different in depth.

Why this matters for DTF: LINKO tested this on white fabric, with one consumable set and one print profile. Pure black (RGB 0/0/0) and dark greys (RGB 30/30/30, 50/50/50, 80/80/80) were printed on the same fabric. The depth differed clearly, and the higher the grey value, the greyer the printed result. Changing the black in the image to true pure black is therefore an effective fix.

Quick check: click the black area with the Eyedropper Tool and see whether it reads 0 / 0 / 0. Chapter 2 gives the steps.

2. First decide: image or equipment

Before changing anything, confirm which side the problem is on. No external tools are needed. This check costs the least and prevents wasted work later.

2.1 Check with the Eyedropper Tool (main check)

Open the image in Photoshop and select the Eyedropper Tool.(See Fig. 2.1-1)
In the options bar, set Sample Size to 3 by 3 Average. This avoids an error from a single pixel.(See Fig. 2.1-2)
Open the Info panel: click Window → Info.(See Fig. 2.1-3)
Move the eyedropper over the black area that prints grey. Read the RGB values in the Info panel.(See Fig. 2.1-4)

Compare the reading against the table below:

Eyedropper reading	What to do next
0 / 0 / 0	The area is already pure black. No further change to the black in the image is needed. If the print still looks grey, troubleshoot the printing side with Troubleshoot Print Color Differences, or contact technical support and test another print profile. This document ends here.
Not 0 / 0 / 0 (for example 30/30/30 or 50/50/50)	If the area is meant to be pure black in the design but does not read 0 / 0 / 0, continue with chapter 3. An area that is dark grey by design is not a fault.

Note: If the image has several black areas, move the eyedropper over each one. If an area is meant to be pure black in the design but does not read 0 / 0 / 0, handle it with this document. An area that is dark grey by design is not a fault.

2.2 Secondary check (when the eyedropper is not convenient)

What you see	Where it belongs
Colors overall are not deep enough, or look grey	This is not only a black problem. Troubleshoot layer by layer with 3.1.16.
Banding across the print	Equipment side. Unrelated to image editing. Contact technical support.

3. Fix the black

3.1 Identify the type of design, then choose the method

Different types of design need different methods. Use the table below to identify your image first.

Type of design	How to identify it	Method
Design with clearly separated colors(logo, text, flat illustration)	The design is made of solid color areas, with no gradient and no shadow detail.	1. Color Range, then fill with pure black (multi-color design)2. Drag the Levels black point into position (single-color design)
Photo, or a design with shadow detail(shadows, gradients, tonal transitions)	The design has gradients, shadows, or texture, or the black sits among other dark colors.	Drag the Levels black point in small steps and watch the shadow areas. Going too far crushes the shadow detail into a solid block.

Note: A quick way to decide: enlarge the image. If it contains only solid color areas with no gradient transition, it is the first type. If it has tonal gradients, shadows, or texture, or the black sits among other dark colors, it is the second type.

3.2 Method 1: push the black to pure black with Levels

The black point slider in Levels is on the left. It forces every pixel darker than that value to pure black (RGB 0 / 0 / 0).

One action covers two common complaints. First: one black area is not black enough. Drag the black point past that grey value. Second: the whole image looks grey. The shadow areas across the image are set to zero together.

Steps:

Click the black area that prints grey with the Color Sampler Tool. The color is now sampled, and the Info panel shows its RGB values.(See Fig. 3.2-1/ 3.2-2)
Click Image → Adjustments → Levels(shortcut Ctrl + L).(See Fig. 3.2-3)
Drag the black point slider on the left of Input Levels to the right. Watch the RGB values in the Info panel.
Stop when the black area reaches pure black, which is R 0 / G 0 / B 0.
Click OK.(See Fig. 3.2-4)
Export a PNG with a transparent background as described in Check Print-Ready Images chapter 4.

Note: The Color Sampler Tool leaves a fixed sample point on the image, and its values stay visible in the Info panel. While you drag the black point slider, you can therefore watch the values move towards 0, instead of judging by eye.

Side effect (important)

Important: The Levels black point slider affects every darker area in the image, not only black. Set too high, it can turn dark blue, dark red, and shadow areas into a solid black, which loses detail. After the adjustment, always check those areas.

How to check: click other dark areas in the image with the Eyedropper Tool. If an area that was dark blue, for example 20 / 20 / 60, now reads 0 / 0 / 0, the black point has gone too far. Drag it back.

3.3 Method 2: Color Range and fill with pure black

When the image contains dark colors that must be kept, a whole-image Levels adjustment is not suitable. Use a selection instead, and change only the black area.

Steps:

Click Select → Color Range.2.(See Fig. 3.3-1)
Click the black area in the image with the eyedropper in the window.(See Fig. 3.3-2)
Adjust the Fuzziness value and watch the white area in the preview. Set “Selection Preview” to “Grayscale” to see the selection more clearly. Adjust until the white area covers exactly the black you want to change.
Click OK to create the selection.(See Fig. 3.3-3)
Set the foreground color to pure black (R 0 / G 0 / B 0), then press Alt + Backspace to fill.(See Fig. 3.3-4/ 3.3-5)
Press Ctrl + D to deselect. Check with the Eyedropper Tool, then export.(See Fig. 3.3-6/ 3.3-7)

Note: A higher Fuzziness value selects a wider range of colors. Set too high, it also selects dark grey and shadow areas and fills them solid black. Set too low, part of the black is missed. Watch the preview while adjusting. Do not use a fixed value.

4. Confirm and export

Confirm each item before exporting:

The black area reads 0 / 0 / 0. Re-check with the Eyedropper Tool.
Other dark areas have not been forced to pure black, and the shadow detail is intact.
No new problem has appeared at the edges of the design.

When everything is confirmed, export a PNG with a transparent background as described in Check Print-Ready Images chapter 4.

Note: Save a PSD source file as well. Levels and fill are destructive edits, so a source file makes later changes easier. Do not overwrite the original file.

5. Situations this document does not cover

Situation	Where to go
The black already reads 0 / 0 / 0 but still prints grey	No further change to the black in the image is needed. Troubleshoot the printing side with Troubleshoot Print Color Differences, or contact technical support.
Banding across the print	Equipment side. Contact technical support.
The black is fine; you only want stronger, more saturated color overall	Why Print Colors Differ from Screen section 4.3. This is a preference adjustment and is out of scope here.
The image itself is blurred or has too few pixels	Check Print-Ready Images, sections 2.1 and 2.2.

6. About “rich black”

When searching for information about printing black, you may find the “rich black” method. It sets black areas to C100 M100 Y100 K100, stacking four inks to deepen the black.

Why this matters for DTF: That method is designed for traditional offset printing. There, the CMYK values in the file decide the ink on the plate directly, with no recalculation in between, so the designer sets the mix. DTF is different. The RIP software (PrintFactory) recalculates the ink for each channel according to the print profile, and the profile carries an ink limit. Anything above that limit is cut off automatically. Stacking ink in the image therefore sends nothing extra to the printhead.

LINKO test result (for reference)

Test conditions: white fabric, one consumable set, one print profile
Result: rich black and pure black showed no clear difference. Single-channel black (K100) printed darker than rich black.

Note: This test covered one condition set only. Machines use different print profiles. Consumables and fabric also affect the result. Treat the conclusion above as a reference, not as a universal one. We publish the result so that you do not have to run the test yourself.

Recommendation: converting to CMYK and filling rich black is not worth the effort. Setting the RGB values to 0 / 0 / 0 as described in chapter 3 is simpler and does the same job in one step.

You can verify this on your own machine and consumables if you want to. Converting to CMYK cannot be undone, so keep the original file first. To keep CMYK, use TIFF, PSD, or PDF. PNG is not used to keep CMYK, and JPG is not a print delivery format for LINKO DTF. See Check Print-Ready Images section 2.4.

7. Frequently asked questions

Q: People online say to use “rich black”. Do I need to?

A: This is not worth the effort. Setting the RGB values to 0 / 0 / 0 as described in chapter 3 is simpler and does the same job in one step. Rich black is a method for traditional offset printing. In DTF, the RIP software (PrintFactory) recalculates the ink and applies an ink limit. Stacking ink in the image therefore sends nothing extra to the printhead. Chapter 6 gives the full explanation and the LINKO test result.

Q: The black looks black on screen but prints grey. Why?

A: A color that looks black on screen is not always pure black. RGB 50/50/50 is dark grey, while RGB 0/0/0 is pure black. Viewed on its own, the difference is hard to see. In testing, the two printed on the same fabric were clearly different in depth. Judge the black by its values with the Eyedropper Tool, not by the screen.

Q: After the adjustment, other colors in the image changed too. Is that normal?

A: No. The Levels black point has gone too far. The black point slider affects every darker area in the image, not only black. Set too high, it can turn dark blue, dark red, and shadow areas into a solid black, which loses detail. Undo, lower the value, or use the selection method in section 3.3 instead.

Q: The black is fixed, but the image still feels weak overall. Can I adjust that too?

A: You can, but that is a preference adjustment, not a correction. See Why Print Colors Differ from Screen section 4.3. Before adjusting, confirm that printing itself is working. If there is a problem on the equipment side, adjusting the image only hides it, and the problem returns with the next normal image.

Q: Do I have to use Photoshop? Can I use other software?

A: You can use other software. This document uses Adobe Photoshop as the example. Any image editor that can select a color, adjust brightness, and fill a color will work. Feature names differ between applications. What matters is the same result: the black area reads 0 / 0 / 0.

8. Related Documents

8.1 Image Preparation

Check Print-Ready Images— Entry document for this set. The 7 checks to run before printing.
Clean Image Edges— White edges, grey edges, and unwanted semi-transparent edges.
Troubleshoot Print Color Differences— If the black is already pure black but still prints grey, troubleshoot with this document.
Why Print Colors Differ from Screen— For preference adjustments, see section 4.3.

8.2 RIP Software (PrintFactory) Settings

Set White Ink Usage, Set White Undercoat Method— The white ink underbase affects the maximum color brightness.
Select ICC Profile— Test another print profile.

LINKO Technical Support
Email: support@dtflinko.com
Website: www.dtflinko.com