Preparing a Photo or JPG for Laser Engraving

## Why Most Photo Engravings Fail The laser can only fire or not fire — there are no actual gray tones. Every mid-tone has to be faked through dithering, and how well that works depends entirely on what you hand it. Send a low-contrast, undersized JPG and you'll get mud. Prep it properly and you get results that look like they came from a proper UV printer. ## Choosing the Right Photo Not every image engraves well. Best candidates: - **High contrast** — clear separation between light and dark areas - **Simple subject** — one face, one pet, one object. Not a crowd. - **Sharp focus** — blur in the photo = blur in the burn, non-negotiable - **Front lighting** — flat even light shows detail. Harsh side shadows block it. Avoid low-contrast images (foggy, overcast outdoor shots), very busy backgrounds, and anything with fine detail under 2mm at your planned output size. ## Step 1: Convert to Grayscale Open in any photo editor — GIMP (free), Photoshop, Affinity Photo, even Apple Photos for basic adjustments. Convert to grayscale mode. This forces you to see what the laser sees — luminosity values only. A red shirt and a green bush can have identical grayscale values. You need to know that now, not after the burn. ## Step 2: Levels and Contrast — the Most Important Step Pull up **Levels** or **Curves** (Ctrl+L in most apps): - Drag the **white point** (right triangle under the histogram) inward until the lightest meaningful area approaches true white - Drag the **black point** inward until the darkest shadow detail approaches true black - Nudge the **midtone** slider to taste — right = darker overall, left = lighter Goal: you want a full-range image that uses the entire 0-255 tonal spectrum. A flat, low-contrast histogram means a flat, washed-out burn. **For portraits:** slightly darken the midtones for more depth. The face should have strong shadow definition. ## Step 3: Optional Sharpening Apply Unsharp Mask: **Radius 0.5-1px, Amount 60-80%**. This exaggerates fine edge detail which translates to crisper rendered dither patterns. Too much creates halos — stop before that point. ## Step 4: Export at the Right Resolution Export at the **exact DPI you plan to engrave at**, at the **physical size** you want. If engraving at 254 LPI (0.1mm line interval) at 100mm × 100mm, export at 254 DPI at 100mm × 100mm. That's roughly 1000 × 1000 pixels. More pixels adds no detail. Fewer pixels = visible pixelation in the burn. **Quick reference:** - 254 LPI → export at 254 DPI at final physical size - 318 LPI → 318 DPI - 508 LPI → 508 DPI ## Step 5: Import and Set Image Mode in LightBurn Import the image → select it → click the layer color square → set mode to **Image** (not Fill, not Line). Then choose your **dither mode**: | Mode | Best For | |------|----------| | **Jarvis** | Photos — the most popular all-rounder | | **Floyd-Steinberg** | Photos — slightly coarser than Jarvis, some prefer on dark woods | | **Stucki** | Very detailed photos, fine features | | **Threshold** | Line art, logos, anything that should be solid black or white | | **Grayscale** | Variable power engraving — excellent on well-tuned machines, inconsistent on others | | **Ordered** | Geometric dot pattern — artistic/retro look | Start with **Jarvis**. It handles most photos on most machines reliably. ## Step 6: Lines Per Inch (LPI) Set in the layer settings: - **254 LPI** (0.1mm) — standard starting point, fast enough for production - **318 LPI** (0.08mm) — noticeably finer detail, ~25% slower - **508 LPI** (0.05mm) — very fine, for small highly-detailed work only, very slow **The higher the LPI, the slower the job.** A 100mm × 100mm photo at 508 LPI can take 45+ minutes on a diode laser. 254 LPI takes 10-15 minutes. ## Test Before You Commit Crop a 30mm × 30mm section from the most important area of the image. Run it at full settings on a scrap piece of the same material. Check: - Is the contrast right? Too light = increase power or reduce speed. Too dark = reduce power or increase speed. - Is the detail there? If not, check image resolution. - Is there banding? Check if your laser's power response is linear. Adjust contrast non-destructively in LightBurn's **Image Properties** panel (right-click the image) without going back to the photo editor. ## Material-Specific Tips - **Basswood/Alder** — fastest and cleanest. Start at 3000mm/min @ 40% on a 20W diode. - **Bamboo** — dense, needs 15-20% more power than basswood. - **Slate** — no dithering needed. Go grayscale mode, variable power, gorgeous results. - **Anodized aluminum** — high-contrast marking only. Threshold mode, not dither. - **Dark leather** — Jarvis at moderate power. Very sensitive to over-burning.

🔧 Related tool: Laser Image Prep Tool