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What Is HueForge TD? Transmission Distance Explained

Updated 2026-06-11 · by Jay

HueForge turns flat prints into images by stacking thin, partly-transparent layers of filament — and how much light each filament passes is everything. That property is TD: transmission distance.

The concept

Hold a strand of white PLA up to a lamp: light glows through. A strand of black: nothing. TD puts a number on that difference — roughly, how many millimeters of this filament does light penetrate before it's effectively blocked?

  • TD 0.5–2 (opaque): blacks, deep blues, heavily pigmented colors. One or two layers fully establish the color — perfect for outlines and dark detail.
  • TD 3–6 (mid): most standard colors. The workhorses of a HueForge palette.
  • TD 8–15+ (translucent): whites, naturals, pastels. Light passes through many layers, which is what creates HueForge's smooth tonal gradients.

Why it matters more than color

Two filaments can look identical on the spool and behave completely differently in a lithophane-style print, because what HueForge cares about isn't reflected color — it's transmitted light. A print planned with wrong TD values comes out muddy, banded, or washed out, no matter how carefully the colors were chosen.

Measuring and trusting values

TD is measured by printing a stepped swatch and finding where backlight stops changing — or estimated with tools like calibrated light sensors. Published values vary between sources because pigment batches vary. FilaScope stores a confidence level with every TD value (verified community measurements rank above estimates) — check it in the TD database.

Building a starter palette

A reliable first set: a high-TD white (the light engine of every print), a low-TD black (detail and contrast), and two or three mid-TD colors that match your subject. The TD database pairs each candidate with its current best price, so building the palette doesn't mean overpaying for it.

FAQ

What does a TD value mean in plain terms?
TD is the depth of plastic (in millimeters) at which a filament stops passing meaningful light. Low TD (0.5-2) blocks light quickly — strong color in thin layers. High TD (5-15+) is translucent — color builds gradually across many layers.
Is a higher or lower TD better?
Neither — they do different jobs. Low-TD filaments define dark details; high-TD filaments create smooth gradients. A good HueForge palette mixes both, plus a high-TD white as the light base.
Why do TD values differ between sources?
Measurement methods and batches vary. Pigment load changes between production runs, and even nozzle temperature shifts effective TD slightly. Treat published values as a starting point and calibrate your slicer's value to your spool.
Where can I find TD values for my filament?
FilaScope's TD database tracks thousands of filaments with TD values and confidence levels, paired with live prices — every filament page shows its TD when one is known.