The reduction formula here applies to a dot pattern that is already fixed in a raster image and then printed smaller. CSP’s live Tone effect can be regenerated at export. Check the Comic export settings and whether frequency follows output scale or layer settings before using the inverse calculation.
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Choose the export behavior first
The reduction formula here applies to a dot pattern that is already fixed in a raster image and then printed smaller. CSP’s live Tone effect can be regenerated at export. Check the Comic export settings and whether frequency follows output scale or layer settings before using the inverse calculation.
When frequency follows layer settings during a scaled export, the specified LPI can be retained at the final size. Do not replace 60 LPI with 42–43 LPI automatically. The calculation below is for a workflow that actually scales the fixed dot spacing; confirm it on a small export before processing every page.
What the effective line count is
Line count (lines per inch, or LPI) is the number of screen-tone dot rows packed into one inch, and dot spacing works out to 25.4 ÷ LPI in millimeters. At 60 LPI that's roughly 0.42mm — 10px on a 600dpi source page. Shrink the page for print and that spacing shrinks by the same ratio. What matters to the reader is the line count measured on the printed sheet after that shrink — the effective line count — not the LPI set on the source page.
Reducing a page doesn't remove any source pixels, so resolution isn't the problem. What actually gets smaller is the dot itself on paper, and that's where ink bleed and the print shop's own reduction processing start to bite.
Calculating effective line count from a reduction ratio
Reduction ratio is print width ÷ source width, and effective line count is LPI ÷ reduction ratio. For common doujinshi size pairs, here's what a 60 LPI tone turns into:
- Print a B4 (257mm) source at B5 (182mm) and the reduction ratio is 0.708 — 60 LPI becomes roughly 84.7 LPI.
- Print an A4 (210mm) source at A5 (148mm) and the reduction ratio is 0.705 — 60 LPI becomes roughly 85.1 LPI.
- Print a B5 (182mm) source at A5 (148mm) and the reduction ratio is 0.813 — 60 LPI becomes roughly 73.8 LPI, a smaller jump.
- For that same B4-to-B5 reduction, an 85 LPI tone on the source becomes roughly 120 LPI — raise the source line count first and the increase scales up right along with it.
Fine screens need an output-specific check
At 100 LPI the interval is 0.254mm, or 6 pixels at 600 dpi. That is a sampling example, not a universal danger threshold. The density, dot shape, paper, ink spread and printing process determine how well individual dots and white gaps survive. A low-frequency dark tone can also fill in; a suitable press can reproduce frequencies above 100 LPI.
Use the printer’s recommended frequency and density range. Increasing raster resolution gives each dot more pixels but does not remove physical dot gain. Inspect the final export after any resampling and use a proof for production decisions.
Working backward from print size to source line count
If your print size is already decided, you can work backward to the line count you should set on the source page.
- Decide the effective line count you want after printing. For black-and-white interior pages, around 60 LPI is a manageable target.
- Work out the reduction ratio (print width ÷ source width). Printing a B4 source at B5 gives 182 ÷ 257 = 0.708.
- Calculate source line count = target effective line count × reduction ratio. 60 × 0.708 = 42.5, so set the source to 42-43 LPI.
- Check that the resulting dot spacing isn't too fine for your source resolution. At 600dpi, 42.5 LPI gives a spacing of roughly 14px — plenty of room to render the dot shape cleanly.
Enter this inverse-calculated frequency in CSP only when the workflow actually scales the fixed dot spacing. When the Tone effect is generated on export with frequency following layer settings, use the intended final frequency on the layer instead; do not apply the inverse calculation again.
For a tone you are about to add, Layer menu > New Layer > Tone opens the Simple tone settings dialog, and the number you worked back to goes into Frequency there. Density and Angle are set in the same dialog, and the preview beside the fields redraws as the actual halftone screen while you type.
To change the line count of a tone already on the page, select that layer and edit Frequency in the Layer Property palette instead. Its angle lives in the same palette, under Angle inside the expanded Dot settings.
Checking how it looks on screen
The preview compares frequency and dot spacing. Calibration aligns physical lengths such as the 100mm reference only. The monitor grid can create false moiré and apparent density changes, so the display cannot approve print moiré, clogging or density. Inspect the final export at 100% for pixel structure, and use a print or proof under the required conditions to judge production.
Sources and verification conditions
Sources checked 2026-09-06. Existing screenshots are from CSP 5.0.4; UI labels can vary by version.