Color Separation for Screen Printing — Works With Vector, Raster, or Both

Color separation is one of the most technical steps in screen printing. Get it wrong and you get gaps between colors, ink mixing where it shouldn't, or a final print that looks nothing like the original artwork. It's the step that determines whether the job comes out clean or goes back for a reprint.

OmniSeps handles the entire process automatically — and it works with whatever format your design is in.

Designed for Vector, Ready for Raster

KnockLayer is built around the most common screen printing workflow: vector and graphic-style artwork, where each color lives on its own Photoshop layer. Logos, apparel graphics, flat-color illustrations — set up your layers the way you already do, and KnockLayer separates them automatically.

It also handles raster layers and mixed designs — a painted texture, a photographic element, a blended component mixed in with flat colors. Every layer gets its own spot channel regardless of how it was built. If your file contains vector or shape layers, rasterize them first and KnockLayer takes it from there.

Layer Compatibility

KnockLayer — and the preprocessing tools that feed into it (Sort Bright, Merge Same Color, CutAll) — work with raster layers only. Before running any of these tools, make sure your document contains no non-raster layers.

These layer types block the entire operation — the tool stops and identifies the problem layer:

• Vector / path layers
• Shape layers
• Solid Color fill layers
• Text layers
• Gradient layers
• Pattern layers

Go to Layer > Rasterize > Layer to convert any of these, then run the tool again.

These layer types are automatically skipped — the operation continues without them:

• Locked layers
• Group / LayerSet layers
• Empty layers (zero pixel area)

No Color Limit

Some tools cap out at a fixed number of colors. KnockLayer doesn't. Whether your design has 4 spot colors or 24, every layer becomes its own channel. The separation scales with the job.

Ink Order — Standard or Custom, Your Call

The standard rule in screen printing is light inks first, dark inks last. This ensures proper coverage on dark garments and prevents darker inks from muddying lighter ones underneath. OmniSeps has a dedicated Sort Bright feature that automatically reorders your layers from lightest to darkest with one click — the standard, handled automatically.

But the order is fully customizable. If your design needs a specific print sequence that's different from the standard — a particular creative effect, a shop preference, a client requirement — arrange the layers yourself before running KnockLayer. The separation follows whatever stack you set up. You always have full control over print order.

Starting From a Messy Client File?

KnockLayer works best when the file coming in is already clean — one layer per ink color, no overlapping pixels, layers in the right order. Most client files aren't.

If you're dealing with duplicate color layers, pixel collisions, or a randomly stacked layer order, OmniSeps has a built-in preprocessing pipeline that fixes all of that before KnockLayer runs. Four tools, run in sequence:

1. CutAll — removes pixel overlap between layers
2. Merge Same Color — consolidates layers that share the same ink color
3. Sort Bright — reorders layers from light to dark
4. KnockLayer — runs the full separation

Read the full guide: How to Clean Up Any Client File Before Separation →

What Happens During Separation

Once your layers are ready, KnockLayer runs through the full separation automatically — every step handled without manual intervention.

Color detection

KnockLayer automatically detects the color of each layer directly from Photoshop — no manual color picking needed.

Spot channel creation

Each layer becomes a dedicated spot channel named after that layer. The channel is built from the layer's own transparency, so the shape is always pixel-accurate to the artwork.

Trapping

KnockLayer expands each spot channel to create an overlap between adjacent colors — preventing white hairline gaps on press from screen misregistration. The expand size is set directly from the Expand input field in the VECTOR tab panel, so you can dial in the trapping amount that works for your press and registration tolerance.

Knockout

Ink on each channel is kept from overlapping during the print process — colors stay accurate and true to the original design. Everything runs automatically with no additional setup needed.

Outer cleanup

Every spot channel is guaranteed clean and tight, covering only the intended design area. No excess ink bleeds outside your artwork boundary.

Mixing Vector and Raster? Add Manual Colors After

If your design combines vector artwork with raster elements and you need to add extra spot color channels on top of what KnockLayer already built — OmniSeps has a manual color separation menu for exactly that.

After KnockLayer finishes, open the manual separation options and add individual color channels one by one. Each color — Blue, Red, Green, Orange, and many more — can be added as a separate spot channel to complement your existing separation. The manual channels stack cleanly on top of what KnockLayer already produced.

This is the workflow for complex mixed designs: let KnockLayer handle the automatic separation first, then extend it manually with whatever extra colors your design needs.

Your Original Design Is Never Touched

KnockLayer is fully non-destructive. Every layer stays exactly as it is throughout the entire process. The MERGED composite is created as a new layer stamped from what's visible — the originals are untouched.

Receive a revision from the client? Update the layers and re-run. You're not rebuilding from scratch.

The Result

When KnockLayer finishes, you have:

• A spot channel for every color in your design, named after each layer
• Trapping applied between every adjacent color
• Clean knockouts — no ink stacking or mixing
• A MERGED composite layer showing the full combined result
• A T-Shirt Color channel for previewing the design on a garment

Everything print-ready. No cleanup required.

Ready to Try It?

KnockLayer and Sort Bright are both built into OmniSeps, a Photoshop plugin designed specifically for screen printing.

Get OmniSeps →

FAQ

What type of designs work with KnockLayer?

Any design where each ink color is on its own Photoshop layer. If your artwork comes from vector objects — from Illustrator, CorelDraw, or any vector tool — rasterize the layers in Photoshop first before running KnockLayer. Once rasterized, KnockLayer handles everything automatically. Mixed raster designs work the same way.

Is there a color limit?

No. KnockLayer processes every layer in the document. 4 colors or 24, every layer gets its own spot channel.

Can I use a custom ink order instead of light-to-dark?

Yes. Light-to-dark is the standard and Sort Bright handles it automatically, but the order is fully customizable. Arrange your layers in any sequence before running KnockLayer and the separation follows your stack exactly.

Can I adjust the trapping size?

Yes. The expand size used for trapping is customizable. Set it to match your press tolerance and registration capability.

What is trapping in screen printing?

Trapping is an overlap between adjacent colors that prevents white hairline gaps from appearing when screens shift slightly on press. KnockLayer applies this automatically to every edge, with a customizable expand amount. Not sure what trapping size to use for your setup? Use the OmniSeps Trapping Calculator to find the right value for your press.

What is knockout in screen printing?

Knockout means each color removes the area of colors beneath it so inks don't stack and blend on press. KnockLayer calculates and applies all knockouts automatically based on your layer stack.

Does KnockLayer change my original layers?

No. KnockLayer is fully non-destructive. All original layers are untouched. The MERGED layer is created separately as a composite — your source layers are never modified.

What if I receive a messy client file with overlapping layers or duplicates?

OmniSeps has a 4-step preprocessing pipeline for exactly that. Read the full guide →