Image Preparation for Engraving

A great laser engrave starts with image prep, not laser settings. Spend 5 minutes adjusting levels and sharpening; save hours of failed test pieces. The same workflow applies to wood, metal, slate, and tile photos across fiber, CO2, and diode.

The universal image-prep workflow

1. Source quality: 600+ DPI at final size. A 6×8" portrait needs ~3600×4800 pixels.
2. Convert to grayscale.
3. Crop to final aspect ratio. Don't let Lightburn distort.
4. Levels adjustment. Drag black point and white point inward to anchor pure 0 and pure 255.
5. Brightness / contrast. Bump contrast +20 typical.
6. Curves adjustment for substrate (lighten midtones for wood; darken midtones for tile).
7. Unsharp mask. Radius 2-3px, amount 50-80%.
8. Dehaze if outdoor / fog photo. Photoshop has this; GIMP needs a script-fu equivalent.
9. Save as PNG at the final laser size and resolution.

The substrate-specific tweaks

Substrate	Adjustment	Why
Maple, basswood	Lighten midtones	Wood burns dark fast, need lighter midtones to preserve highlights.
Cherry, walnut	Lighten midtones + boost contrast	Already-dark substrate; need extra contrast for highlights to read.
Slate	Darken midtones	Light areas need to fully ablate the paint to read white.
Norton white tile	Darken midtones + boost contrast	Same as slate, need full ablation in light areas.
Stainless steel	Standard levels, no special tweak	Even tonal response.
Anodized aluminum	Standard levels	White-on-color contrast is naturally high.
Veg-tanned leather	Lighten midtones slightly	Leather burns dark; preserve light tones.

Levels: the most-impactful single step

Open in Photoshop / GIMP / Affinity → Levels (Ctrl+L in Photoshop):

1. Look at the histogram. Pure black should reach the left edge; pure white should reach the right edge.
2. If histogram has a gap on the left, drag the black point slider RIGHT to where data starts.
3. If histogram has a gap on the right, drag the white point slider LEFT to where data ends.
4. This stretches your tonal range to use the FULL 0-255 spectrum.
5. Adjust the middle (gamma) slider to brighten or darken midtones for the substrate.

Unsharp mask: make detail pop

Unsharp mask increases edge contrast, sharpens the image without over-processing:

• Radius: 1-3 pixels for most photos. Higher = larger halo around edges.
• Amount: 50-100% typical. Higher = more aggressive sharpening.
• Threshold: 0-3 typical. Lower = more aggressive (sharpens noise too); higher = only sharpens larger features.
• Goal: face/eyes/details look crisp without "halo" outlines around features.

Dither selection per substrate

Substrate	Best dither
Maple, basswood (light wood)	Stucki, smoothest gradients
Cherry, walnut	Stucki or Atkinson
Slate	Jarvis, smoothest contrast
Veg-tanned leather	Stucki, tactile gradient
Norton white tile	Jarvis, community standard
Stainless steel (fiber)	Jarvis or Stucki
Anodized aluminum	Jarvis
Acrylic frosted	Atkinson, light touch

The DPI / resolution rule

Substrate	Typical DPI	Equivalent interval
Wood photos (general)	318 DPI	0.08 mm
Slate, Norton tile	423 DPI	0.06 mm
Leather	318 DPI	0.08 mm
Photo on metal (fiber)	1016 DPI	0.025 mm
Coin relief (fiber)	3175 DPI	0.008 mm

Higher DPI = finer detail BUT longer engrave time + more potential for char buildup. Match DPI to viewing distance.

The 30×30mm corner test

Before running a full image, ALWAYS engrave a 30×30mm corner test:

• Verify contrast envelope (no fully-black blobs, no fully-white voids).
• Verify dither pattern reads cleanly.
• Verify skin tones look natural.
• Verify total time multiplier matches the full piece.

If the test is wrong, adjust source levels OR change dither. Run another test before the full piece.

Common image-prep mistakes

• Source too low resolution. Re-shoot or upscale carefully (Topaz Gigapixel works well for upscaling photos).
• JPEG compression artifacts. Always start from PNG/TIFF if possible. JPEG halos engrave visibly.
• Levels not stretched. Engrave looks muddy because tonal range is compressed.
• No unsharp mask. Engrave looks soft / out of focus.
• Color image not converted to grayscale. Some lasers handle RGB but most strip color anyway; convert deliberately.
• Resizing AFTER processing. Always do levels + sharpen at the FINAL size to preserve detail.

Lightburn's Adjust Image tool

Right-click any image in Lightburn → Adjust Image. Non-destructive overlay tuning:

• Brightness / Contrast / Gamma
• Sharpen / Unsharp Mask
• Material presets per substrate

Save these adjustments with the project. Re-open later and they persist.