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 Depth Studio 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: 3D & Depth
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.