A depth map is a grayscale height field: white is the highest point, black is the lowest, and every gray level in between is a physical height your laser or CNC will carve. The number of gray levels available — the bit depth — decides whether your relief comes out as a smooth sculpture or a terraced wedding cake.
The math that causes banding. An 8-bit grayscale image has 256 possible levels. Carve a 2 mm deep brass relief from an 8-bit map and each gray step is a ~0.008 mm terrace — sounds small, but the terraces cluster on gentle slopes (faces, drapery, sky gradients) where dozens of adjacent pixels share one level. The result is the familiar topographic-ring artifact. A 16-bit map has 65,536 levels — 256× the height resolution — so the same slope is described continuously and the terraces disappear below the resolution of the machine itself.
Where 8-bit hides and where it hurts:
- Shallow wood/slate photo relief: material texture usually masks 8-bit terracing. You can get away with it. - Deep relief in brass or steel (MOPA, multi-pass): terraces become physical ledges you can see and feel. 16-bit is mandatory. - Coins and medallions: the classic failure case — smooth cheeks and domed fields band first. This is why our Coin Designer 3D pipeline exports a 16-bit depth map and exposes smoothing and tuning before you cut — and why, for the smoothest possible domed field, a deterministic relief beats a sculpted one. - CNC carving from the same height field: ball-nose toolpaths amplify terraces into visible scallops. 16-bit again.
The "fake 16-bit" trap. Plenty of free depth-map generators output a file *saved* as 16-bit that was *computed* at 8-bit precision. Saving 256 levels into a 65,536-level container adds zero height information — the histogram shows a comb of empty gaps, and the engraving bands exactly as if it were 8-bit. If a tool doesn't state its working precision, test it: generate a smooth gradient subject and inspect the histogram.
We ran that test on ourselves. It would be easy to end this section by telling you Reticle Red is 16-bit end to end, and it would not be true. Here is the actual split. The deterministic engines — the free zero-credit conversion, V-Carve Text, and geometric relief — accumulate height in floating point and quantise once, so they fill the 65,536-level range and pass the histogram test above. The AI depth route in Neural Relief and Coin Designer's 3D pipeline exports the same 16-bit PNG, but the depth and sculpting models behind it return 8-bit payloads, so its real level count is closer to 256 stretched across the range. Range, not information — exactly the trap described above.
That does not make AI Sculpt the wrong tool; it makes it a different one. Sculpted relief compresses depth and domes fields in ways a faithful estimator never will, and that design decision is usually worth more on a coin than raw level count. But if you are fighting visible banding on a deep smooth carve, use a deterministic mode — it is free, it is repeatable, and it is the one that actually fills the range. Check the Community Gallery for real brass engravings with the exact settings used.
Frequently Asked Questions
Why does my 3D relief engraving show visible steps or rings?
Stair-stepping (banding) in relief engraving is almost always a bit-depth problem, not a machine problem. An 8-bit depth map can only describe 256 height levels, so a smooth slope becomes a staircase of 256 flat terraces — and on deep relief in brass or thick wood, each terrace becomes a visible ring. A 16-bit depth map describes 65,536 levels, so the same slope stays smooth. If a free online depth-map tool does not say what bit depth it outputs, it is almost certainly 8-bit.
When is an 8-bit depth map good enough?
Shallow, single-pass grayscale engraving on wood or slate — where total relief depth is a fraction of a millimeter — usually hides 8-bit terracing inside the material's own texture. The moment you run deep relief (multi-pass brass, MOPA coin work, CNC carving from the same height field), 256 levels get stretched across the full depth and the steps become visible and physical.
How do I check whether a depth map is really 16-bit?
Open it in an image editor and check the image mode (8-bit vs 16-bit channel), then look at the histogram. A file saved as 16-bit but generated at 8-bit precision shows a comb pattern of evenly spaced gaps — stretching 256 levels into a 16-bit container adds range, not information. Run that test on our output too, and here is what you will find: Reticle Red's deterministic engines quantise once from a floating-point accumulator and fill the range. The AI depth route does not, because the depth models behind it return 8-bit payloads that we normalise across the range. Both export a 16-bit PNG; only the deterministic one carries 16-bit worth of distinct heights. If banding on a deep carve is what you are fighting, that is the mode to use — and it costs nothing.