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# Halftone LPI, PPI and DPI: Keep the Grids Separate

> Distinguish halftone frequency, source pixels and output-device dots. Inspect original one-inch SVG grids and prepare a clear brief for your screen printer.

Source: https://perfectvector.com/blog/halftone-lpi-ppi-dpi

Language: en
Author: Irene Kim
Published: 2026-10-22T08:00:00+09:00
Updated: 2026-10-22T08:00:00+09:00

LPI describes halftone frequency, PPI describes raster samples at a placed size, and DPI describes output-device resolution. They count different things. Changing a file's PPI does not choose the printer's halftone frequency, and a vector dot pattern does not become printable merely because its edges stay sharp.

For screen-printing artwork, establish the intended print dimensions and ask the printer who prepares the halftones. Keep continuous-tone source artwork available until the separation and screening workflow is agreed. A printer may want the original image rather than an already screened pattern.

> **Name the grid before changing a number**
>
> Record the source pixel dimensions and placed size, the intended halftone frequency, and the output workflow separately. Confirm the printer's mesh, angle, dot-shape and tone requirements rather than treating a single “DPI” number as the complete brief.

## Separate the three units

A **halftone cell** is one repeat location in the regular dot grid used in this article. The cell can contain a smaller or larger dot to represent different nominal areas. Its pitch is the distance between corresponding neighboring cell centers.

| Unit                 | What it describes here                                          | Question to ask                                                        |
| -------------------- | --------------------------------------------------------------- | ---------------------------------------------------------------------- |
| LPI, lines per inch  | Repeats of the regular halftone screen along its grid direction | How fine is the intended halftone grid?                                |
| PPI, pixels per inch | Raster pixels assigned to each inch at the placed size          | How many source samples are available?                                 |
| DPI, dots per inch   | Output-device resolution                                        | Which output process and device settings will produce the separations? |

[Adobe's printer-resolution guidance](https://helpx.adobe.com/photoshop/desktop/crop-resize-transform/resize-adjust-resolution/printer-resolution.html) distinguishes device DPI from image resolution and defines screen frequency in LPI. Its [printed-image resolution explanation](https://helpx.adobe.com/photoshop/desktop/crop-resize-transform/resize-adjust-resolution/printed-image-resolution.html) relates PPI to pixel dimensions and physical placement.

People sometimes use “DPI” when they mean the image's pixel density. In a handoff, write the actual pixel count and intended print dimensions so that shorthand cannot conceal the source size. The [actual-versus-effective PPI guide](https://perfectvector.com/blog/actual-vs-effective-ppi) covers that placement calculation in more detail.

## Count two original one-inch dot grids

We authored two SVG specimens, each declaring a one-inch square. One contains a 10 × 10 grid of circles, the other a 20 × 20 grid. Both use round dots centered in square cells, an unrotated grid and a chosen nominal circle area of 50% of each cell.

These low frequencies make the geometry easy to inspect. They are illustrative inputs, not recommended screen-printing settings.

For a frequency L, the cell width is `1/L` inch. If each circle occupies half the square cell area, its radius is:

```text
radius = sqrt(0.5 / pi) / L inches
```

| Original specimen | Circles in the one-inch square | Cell pitch | Circle diameter |
| ----------------- | ------------------------------ | ---------- | --------------- |
| 10 LPI            | 100                            | 2.54 mm    | About 2.0266 mm |
| 20 LPI            | 400                            | 1.27 mm    | About 1.0133 mm |

Doubling the frequency doubles the number of cells across either dimension. The total count becomes four times larger, while each circle's diameter halves. The sum of the circles' geometric areas remains half a square inch in either saved file.

**Original digital grid study**

![Actual browser rendering of original 10 and 20 LPI one-inch vector circle grids beside a separate 60 by 60 pixel grayscale source](https://perfectvector.com/blog/halftone-lpi-ppi-dpi/grid-proof.webp)

*The specimens are enlarged for inspection. The two vector grids have equal nominal circle area; the separate raster source illustrates a different sampling grid. This is not RIP output, film, screen exposure, printed tone or a print-quality comparison.*

We reopened the SVGs and counted their circles, checked center spacing and radii, and summed their areas. We also inspected the actual 60 × 60-pixel PNG and verified that the comparison embeds those same source bytes. The browser capture shows these saved original specimens.

A nominal 50% geometric area does not establish a printed 50% tone or a particular perceived gray. We did not expose a screen or print either specimen.

## Keep source sampling separate from the dots

Our separate grayscale ramp contains 60 × 60 pixels. At a chosen one-inch placement, it has 60 PPI. That pixel count is independent of the circles in either vector file; we did not screen the ramp to produce them.

The arithmetic helps distinguish the scales:

```text
60 PPI / 10 LPI = 6 source samples per cell width
60 PPI / 20 LPI = 3 source samples per cell width
```

Those ratios count samples across a nominal cell width. They do not establish a recommended resolution, screening quality or available tonal levels. Image content, rotation, filtering and the printer's screening method remain separate questions.

If you place the same 60-pixel source at two inches wide, its effective density becomes 30 PPI. The stored pixel count has not changed. If an existing vector dot specimen is scaled, its physical cell pitch changes too: a one-inch, 10-cell-wide pattern stretched to two inches has five cells per inch along that direction.

A vector halftone can therefore preserve circular outlines while ending up at the wrong physical frequency. Check the intended size before asking whether the file looks sharp at high zoom.

## Treat device resolution as another grid

Suppose a hypothetical output system uses a regular 600-DPI address grid. A 10-LPI cell width spans 60 nominal device-address intervals; a 20-LPI cell width spans 30. These are `600/10` and `600/20` arithmetic examples. We did not generate output for a device.

A halftone dot is not necessarily one device dot. Nor does a device-DPI number describe the screen mesh or prove that the smallest ink detail will survive production. Adobe's guidance also notes that output devices can use screening methods other than conventional halftoning, so confirm the actual workflow rather than applying one grid model universally.

[ScreenPrinting.com's halftone introduction](https://www.screenprinting.com/blogs/news/a-crash-course-in-halftones-for-screen-printing) discusses grid-based patterns, RIP preparation, dot shape, angle and dot gain. Those production choices require the printer's setup. The original specimens here establish only circle geometry and sampling arithmetic.

## Make the artwork handoff explicit

Send the print provider enough information to distinguish the source from the screened result:

1. **Final dimensions.** Include the intended physical print width and height.
2. **Source type.** State whether the artwork is a continuous-tone image, flat vector shapes or an existing halftone pattern.
3. **Screening owner.** Agree who creates separations and applies the frequency, angle and dot shape.
4. **Production verification.** Ask the printer to check its actual screening output, screen and print proof for the job.

Keep an unscreened master. If an existing pattern is intentional artwork, say that before the provider processes it again. Avoid editing a pre-screened raster merely to make its metadata say a larger number.

## Where PerfectVector fits

If a flat emblem within the design exists only as PNG or JPG and the printer needs editable shapes, [prepare a vector candidate with PerfectVector's screen-printing artwork workflow](https://perfectvector.com/screen-printing-artwork-to-vector). Compare its contours, small gaps and intended solid regions with the source before the printer's prepress review. Keep an existing native vector when available.

Do not automatically trace photographs, gradients or already screened dots. The printer may prefer their original raster sources. PerfectVector does not create named ink separations, choose halftone settings or verify screen and press results. The [T-shirt vector-art guide](https://perfectvector.com/blog/vector-art-for-t-shirts) explains the earlier artwork-format decision.

## FAQ

**Are LPI, PPI and DPI interchangeable?**
No. LPI describes the regular halftone frequency, PPI describes raster samples at a placed size, and DPI describes output-device resolution. State the intended physical size and what each number counts.

**Does a vector halftone have a PPI?**
Its circle geometry has no fixed raster sample grid. Its physical placement still determines cell pitch and LPI, and any rasterized export has its own pixel dimensions and PPI.

**Does 50% circle area guarantee a 50% printed tone?**
No. Our specimens establish geometric area only. Screen preparation, ink transfer and the actual output need the printer's checks and proof.

**Should I convert a halftone photograph to SVG?**
Ask the printer which source it wants. A continuous-tone photograph or existing screened raster may be more useful in its original form; vector recovery is a separate option for suitable flat artwork.

## Sources

1. [Adobe — Printer resolution and screen frequency](https://helpx.adobe.com/photoshop/desktop/crop-resize-transform/resize-adjust-resolution/printer-resolution.html) — Distinguishes output DPI, image resolution and LPI, with device-specific screening limits.
2. [Adobe — Printed image resolution](https://helpx.adobe.com/photoshop/desktop/crop-resize-transform/resize-adjust-resolution/printed-image-resolution.html) — Relates pixel dimensions, placed size and PPI.
3. [ScreenPrinting.com — A Crash Course in Halftones for Screen Printing](https://www.screenprinting.com/blogs/news/a-crash-course-in-halftones-for-screen-printing) — Production context for grid-based halftones, RIP preparation, dot shape, angle and dot gain.

***

Need editable shapes from a flat raster emblem? [Prepare a vector candidate with PerfectVector](https://perfectvector.com/screen-printing-artwork-to-vector), inspect it against the original, and send the checked artwork with a clear size and screening brief to your printer.

## Explore

- [Read the HTML article](https://perfectvector.com/blog/halftone-lpi-ppi-dpi)
- [Woven Label Artwork: Keep a Logo Clear at Small Sizes](https://perfectvector.com/blog/woven-label-logo-artwork.md)
- [Turn a Child's Drawing Into an SVG (Wobble and All)](https://perfectvector.com/blog/childs-drawing-to-svg.md)
- [Product facts](https://perfectvector.com/product-facts.md)
- [FAQ](https://perfectvector.com/faq.md)
- [Pricing and credits](https://perfectvector.com/pricing.md)