How to Dither an Image in Photoshop: The Honest Manual Method

How do you dither an image in Photoshop?

You convert it to Indexed Color mode and pick a dither method — Diffusion, Pattern, or Noise — inside that conversion dialog. Go to Image > Mode > Indexed Color, choose from the dropdown, then adjust the Amount slider while watching the live preview. That's the whole manual process. Everything else in this article is just deciding which of the four options, and which amount, actually fits the image in front of you.

Most tutorials stop at "there's a dropdown, pick Diffusion." That's not enough to get a result you'd actually ship. The dropdown has four options. The amount slider changes the result more than people expect. And the dialog has at least one gotcha that ruins edges if you convert in the wrong order.

What's in the Indexed Color dialog

The Dither dropdown

Once the dialog's open, the Dither field has four choices, documented by Adobe as:

• None — no dithering. Every pixel rounds to the nearest color in the palette. Fast, but it produces visible banding on any gradient or smooth tone.
• Diffusion — an error-diffusion method. Less structured, more natural-looking than Pattern.
• Pattern — a halftone-like square pattern that simulates colors missing from the palette.
• Noise — similar to Diffusion, minus the visible seams Diffusion can leave between tiled sections of a large image.

Preserve Exact Colors and palette type

Preserve Exact Colors protects any color already sitting in the target color table from getting dithered over. Turn it on when the image has text or fine hairline detail you don't want fuzzed by the dither pattern. Leave it off for photographic images, where you want the dither running everywhere.

The palette matters as much as the method. Local Perceptual, Selective, and Adaptive palettes get generated from the image's own colors; a Custom palette loads a fixed set from a file instead. Same Diffusion setting, different palette, visibly different result — a bad palette makes even Diffusion look muddy, no matter how carefully you tune the amount.

What's the difference between Diffusion and Pattern dither?

Photoshop's Diffusion option is an implementation of error-diffusion dithering — the same family Floyd-Steinberg belongs to. It's a feedback process: each pixel's rounding error gets pushed onto neighboring pixels that haven't been processed yet, so the image as a whole approximates the original tone even though no single pixel does exactly. For the algorithm-level comparison, including why Floyd-Steinberg specifically distributes error to four neighboring pixels while denser variants spread it further, see Floyd-Steinberg vs ordered dithering.

Pattern dither works differently. It's ordered dithering — a fixed threshold matrix instead of pixel-to-pixel feedback. Every pixel gets compared against the matrix value at its tiled position, independent of every other pixel. That independence is exactly why ordered dithering is animation-safe: no inter-pixel feedback means no shimmer or crawl between frames, unlike error-diffusion applied frame-by-frame to video.

What dither amount should you use in Photoshop?

Select Diffusion and an Amount slider appears, running 0-100%, controlling what percentage of image colors actually get dithered. Push it higher and more of the image gets dithered — but file size goes up, and, less talked about, so does visible noise in areas that were already flat and clean.

There's no single correct number, but there is a real data point worth having. A Photoshop dithering guide from the OpenRCT2 modding project — written by someone converting hundreds of production sprites against a fixed custom palette — states plainly that "somewhere around 50% usually looks best" for their use case. That's a concrete starting point where Adobe's own documentation stays abstract. Start at 50%. Nudge the slider while watching the live preview. Stop as soon as banding disappears — pushing toward 100% "to be safe" usually just adds grain to areas that didn't need it.

Which dither mode should you pick: Diffusion, Pattern, or Noise?

Diffusion is the default instinct for a reason. It's closest to what a hand-drawn or press-printed dither actually looks like, and it's the mode most comparable to Atkinson dithering's fixed-threshold approach — though Photoshop's dialog has no way to reproduce Atkinson's specific error-distribution pattern natively. Targeting print at a specific screen angle instead of screen display? Pattern is closer to what a press will actually reproduce.

Where does Photoshop's manual method fall apart?

Two failure modes show up consistently, and Adobe's own documentation mentions neither.

Transparency has to be handled before conversion, not after. Convert to Indexed Color first, add transparency afterward, and the pixels along that transparent edge dithered against whatever background color happened to be there at conversion time — a color that was never meant to be part of the image. The OpenRCT2 guide calls this out directly, and notes Photoshop's own post-conversion transparency workflow is more complicated than just doing that step in a different editor first. Get the alpha channel right before you touch Image > Mode.

The dialog has no live preview at full resolution on large files, and the palette recomputes with a visible lag every time you change the amount or palette type — fine-tuning a high-resolution export gets slower than it should be. Worse, the four dither modes are fixed: no adjustable matrix size, no blue-noise option, no way to dial in an Atkinson-style threshold variant, no way to preview against a specific print screen angle or LPI in the same dialog. Doing halftone print prep? The Indexed Color dialog gets you a dithered file. It doesn't get you a file checked against moiré at your actual screen angle.

Photoshop vs kott: which one should you actually use?

Already inside a Photoshop-only pipeline, only need to export one file? The manual method above is genuinely fine. Costs nothing extra, doesn't require leaving the app you're already in.

kott® wins when you're iterating: trying five threshold values on the same photo, or reproducing a specific look like Atkinson that Photoshop's dialog simply can't output. Photoshop wins when dithering is a one-off step inside a bigger Photoshop job and you don't need the extra algorithms.

Try the same settings live in kott — the Diffusion result above took a full menu round-trip to check in Photoshop. The same test runs live there, amount and mode both adjustable in real time.

Frequently asked questions

What is the fastest way to dither an image in Photoshop?

Image > Mode > Indexed Color, set Dither to Diffusion, leave Amount around 50%, and check Preserve Exact Colors if the image has text or fine lines. That's the whole manual path — no plugin required.

Why does my dithered image in Photoshop look banded instead of dithered?

Dither is set to None, or the Amount slider on Diffusion is too low. None applies zero dithering and rounds every pixel to the nearest palette color, which is exactly what produces visible banding on gradients.

What's the difference between Diffusion and Pattern dither in Photoshop?

Diffusion is error diffusion — it pushes each pixel's rounding error onto neighboring pixels, producing an organic, non-repeating texture. Pattern uses a fixed halftone-like matrix instead, which tiles predictably and is safer for animation because frames don't shimmer against each other.

Does Photoshop's dither amount matter, or should it always be 100%?

It matters. 100% dithers every eligible pixel and can bloat file size and add visible noise in flat color areas; practitioners commonly land closer to 50% and adjust by eye against the live preview.

Can Photoshop do Bayer or ordered dithering, or only error diffusion?

Pattern dither is Photoshop's ordered-dithering option — it isn't labeled Bayer, but it works on the same threshold-matrix principle. There's no way to swap in a different matrix size or a blue-noise variant from inside the dialog.