---
title: "Resin exposure at 0.03 mm instead of 0.05 mm layers"
description: "Going from 0.05 to 0.03 mm layers takes about 82% of the exposure, not 60%, if the resin's light penetration depth is 0.10 mm, the value Encrust assumes."
url: "https://encrust.app/blog/resin-exposure-when-layer-height-changes/"
lang: "en"
updated: "2026-10-08"
---

[ Resin printing, file formats and how a slicer works](https://encrust.app/blog/)

Resin printing

# Halve the layer height and the exposure does not halve

[By Vladimir Varvorkin](https://encrust.app/about/) Updated October 8, 2026 5 min read

Going from 0.05 to 0.03 mm takes about 82% of the exposure, not 60%, and halving to 0.025 mm about 78%, not 50%. These figures are computed, not measured, from the Jacobs working curve with a penetration depth of 0.10 mm, which Encrust assumes because no resin it ships states one. Your resin maker's number for your height comes first.

## On this page

1. [The curve](https://encrust.app/blog/resin-exposure-when-layer-height-changes/#the-curve)
2. [The numbers for 0.05 to 0.03 mm](https://encrust.app/blog/resin-exposure-when-layer-height-changes/#the-numbers-for-005-to-003-mm)
3. [How wrong the assumed depth can be](https://encrust.app/blog/resin-exposure-when-layer-height-changes/#how-wrong-the-assumed-depth-can-be)
4. [Why the bottom block is exempt](https://encrust.app/blog/resin-exposure-when-layer-height-changes/#why-the-bottom-block-is-exempt)
5. [What to do](https://encrust.app/blog/resin-exposure-when-layer-height-changes/#what-to-do)

A resin file says 2.5 s at 0.05 mm. Cut at 0.03 mm and Encrust writes 2.05 s, not the 1.5 s that proportion gives. Cut at 0.1 mm it writes 4.12 s, not 5\. Those are the figures for the app’s “Generic resin” (2.5 s normal, 30 s bottom), computed from the formula below. They are not a measurement on any printer or resin.

Note

Every figure here assumes a light penetration depth of 0.10 mm. No resin that Encrust ships states one, so the app uses this single value for all of them. It is a stand-in the project chose, not a value anyone measured. [The sensitivity](https://encrust.app/blog/resin-exposure-when-layer-height-changes/#how-wrong-the-assumed-depth-can-be) is below.

## The curve

Cure depth follows the working curve, the standard cure-depth model of resin printing, usually credited to Jacobs. We cite no paper for it, only [our implementation](https://github.com/vvvlladimir/Encrust/blob/v0.1.0/docs/design/profiles.md). The dose a layer needs is its inverse:

```
Cd = Dp * ln(E / Ec)        E(L) = Ec * exp(L / Dp)
```

In a resin file the terms map like this.

| Term | Meaning                                       | Where it is in the file                                     |
| ---- | --------------------------------------------- | ----------------------------------------------------------- |
| L    | layer thickness, mm                           | layer\_height\_mm (the height the exposure was measured at) |
| E(L) | dose a layer of thickness L needs             | exposure\_s, in seconds, at that height                     |
| Dp   | light penetration depth, mm                   | penetration\_depth\_mm, optional                            |
| Ec   | critical dose, below which resin does not gel | not stored: it cancels                                      |

Encrust never needs `Ec`. It carries a resin’s exposure from the height it was measured at to another by the ratio, which is all that `exposure_for_mm` ( [source](https://github.com/vvvlladimir/Encrust/blob/v0.1.0/crates/printer-profiles/src/exposure.rs)) computes. The [profiles design note](https://github.com/vvvlladimir/Encrust/blob/v0.1.0/docs/design/profiles.md) states the rule:

```
E_new = E_measured * exp((L_new - L_measured) / Dp)
```

Exposure rises by a factor of e for every `Dp` of extra thickness. It does not fall to zero at zero thickness, which is why a thin layer takes more than its share.

## The numbers for 0.05 to 0.03 mm

The factor depends only on the height change and `Dp`. With the assumed `Dp` of 0.10 mm, computed from the formula, not measured:

| From    | To       | Share of exposure kept | Generic 2.5 s becomes                     |
| ------- | -------- | ---------------------- | ----------------------------------------- |
| 0.05 mm | 0.03 mm  | 82%                    | 2.05 s                                    |
| 0.05 mm | 0.025 mm | 78%                    | 1.95 s                                    |
| 0.10 mm | 0.05 mm  | 61%                    | 1.52 s (if the 2.5 s were set at 0.10 mm) |
| 0.05 mm | 0.10 mm  | x1.65                  | 4.12 s                                    |

The carrying is also consistent: going 0.05 to 0.08 to 0.03 gives the same figure as going straight, because the exponents add. A test in the source checks that.

## How wrong the assumed depth can be

The factor for 0.05 to 0.03 mm at three depths, computed from the same formula:

| Dp                | 0.05 to 0.03 mm | 0.05 to 0.10 mm |
| ----------------- | --------------- | --------------- |
| 0.05 mm           | 67%             | x2.72           |
| 0.10 mm (assumed) | 82%             | x1.65           |
| 0.15 mm           | 88%             | x1.40           |

The 0.05 and 0.15 mm rows are what-ifs, not resins we measured. They show the spread: if your resin’s real depth is 0.05 mm, the assumed value writes 82% where the curve gives 67%, and for 0.05 to 0.10 mm it writes x1.65 where the curve gives x2.72, about 40% less exposure than that curve calls for. The gap widens with the distance from the height the resin was measured at.

## Why the bottom block is exempt

Bottom layers are exposed long to bond to the plate, not to cure through a given thickness. Encrust leaves the bottom exposure as it is when the layer height changes ( [profiles design note](https://github.com/vvvlladimir/Encrust/blob/v0.1.0/docs/design/profiles.md)). Going from 0.05 to 0.1 mm raises the generic resin’s normal exposure from 2.5 s to 4.12 s and leaves its 30 s bottom exposure at 30 s. The transition layers ramp between the two, so they move with the normal value.

## What to do

Treat the carried number as a starting point for one printer and one resin. Your resin maker’s exposure for your printer at your layer height comes first. If the maker gives none for 0.03 mm, start from the carried value and print a calibration piece before a real part.

The panel, its “Carried from” label and the button that restores the old value are covered step by step in [Exposure, lift and rest times](https://encrust.app/guides/resin-exposure-lift-rest-settings/). The files that hold a resin’s numbers are in [Printer, resin and support profiles](https://encrust.app/guides/printer-resin-support-profiles/).

If you have measured a resin’s penetration depth, set `penetration_depth_mm` in its resin file and the carrying uses that instead of 0.10 mm.

## Sources

- [Encrust: profiles, "Exposure follows the layer height"](https://github.com/vvvlladimir/Encrust/blob/v0.1.0/docs/design/profiles.md)  · The rule as the app states it, including the bottom block
- [Encrust: exposure.rs](https://github.com/vvvlladimir/Encrust/blob/v0.1.0/crates/printer-profiles/src/exposure.rs)  · The function, the 0.10 mm constant and the tests that pin the numbers

## Read next

- [Exposure, lift and rest times ](https://encrust.app/guides/resin-exposure-lift-rest-settings/)
- [Printer, resin and support profiles ](https://encrust.app/guides/printer-resin-support-profiles/)
- [All posts ](https://encrust.app/blog/)

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