In the workflow
Why Polarity matters
Correct polarity depends on whether exposure creates a lighter or darker mark. It should be tested rather than inferred from screen appearance alone.
Practical check
How to evaluate it
Engrave a small black-to-white reference patch on the actual material. It should reveal which source tones produce the lightest and darkest visible marks before a full photograph is prepared.
Go deeper
How to Prepare a Photo for Slate Laser Engraving
A careful photo-preparation workflow for slate, including polarity, contrast, dithering, sizing, and a controlled material test.
Read the complete guide