Blender optimal noise threshold: which value to use in Cycles

What does the noise threshold do in Cycles?

The setting lives in Render Properties > Sampling > Render. Ticking the Noise Threshold checkbox turns on adaptive sampling. Cycles then estimates how noisy each pixel still is while it renders, and stops sending samples to a pixel once its estimated noise drops below the threshold. Flat, well lit areas such as a clear sky or a matte wall converge quickly and stop early. Glossy reflections, dark corners, hair and volumes keep sampling.

The result is that render time goes where the noise is, instead of being spread evenly over the frame. A lower value means a stricter target: cleaner image, longer render. A higher value means Cycles gives up on each pixel sooner. If you untick the checkbox, adaptive sampling is off and every pixel receives exactly the Max Samples count, which is almost always slower for the same visual quality.

The viewport has its own Noise Threshold in the Viewport section of the same panel. It defaults to 0.1, ten times looser than the render default, which is why the viewport can look clean while the final render still needs work.

How do Noise Threshold, Max Samples and Min Samples work together?

A pixel stops sampling as soon as one of these limits is reached, whichever comes first:

• Noise Threshold: the pixel is considered clean enough.
• Max Samples (4096 by default): the ceiling. Pixels that never reach the threshold, typically in caustics or very dark interiors, stop here.
• Time Limit: an optional cap on the whole render. At 0 there is no limit.

Min Samples is the number of samples every pixel receives before adaptive sampling is allowed to stop it. At 0, Blender picks a value automatically from the threshold. Raise it only if small, bright details get missed: a tiny light in a reflection, or thin highlights that come out as isolated speckles because the pixel looked converged too early.

In practice, the threshold controls the quality of most of the image and Max Samples controls the worst case. If a render is slow because a few areas never converge, lowering Max Samples caps the cost of those areas, at the price of leaving them a little noisier.

Which noise threshold should you use?

These are starting points to test, not rules. Scenes with lots of glass, volumes or indirect light behave differently from a product shot on a plain background.

Animation is the case people get wrong. A denoiser works on each frame separately. When the input is noisy, it makes slightly different guesses on every frame, and fine textures start to crawl or blotches appear in shadows during playback, even though each frame looks fine on its own. A stricter threshold gives the denoiser less to guess.

Also look at the Seed in Sampling > Advanced. The clock icon next to it animates the seed, so the noise pattern changes on every frame. Without it, any leftover noise stays fixed on the screen while the camera moves, which reads like dirt on the lens. With it, leftover noise reads like film grain.

How do you find the right value for your own scene?

1. Set the final resolution, lighting and materials first. Changing them afterwards changes the answer.
2. In camera view, press Ctrl+B and draw a render region around the hardest part of the frame: glass, a dark corner, hair, a volume. Ctrl+Alt+B clears it later.
3. Turn the denoiser off and render the region at 0.1. Note the time shown at the top of the render window.
4. Render again at 0.05, 0.02 and 0.01, each in a different render slot (the Slot menu in the Image Editor header), so you can flip between the results.
5. Turn the denoiser on and repeat with the two most promising values. Compare at 100% zoom, not zoomed out.
6. Keep the highest threshold whose denoised result holds up. For an animation, render five or six consecutive frames at that value and play them back, because flicker only shows in motion.

Clear the render region before the final render, otherwise only that region is rendered.

Should you use the denoiser with the noise threshold?

Usually yes, they are designed to work together. Tick Denoise in the Render section of the Sampling panel and choose the denoiser:

• OpenImageDenoise runs on any hardware and generally keeps texture detail better. It is the usual choice for final frames.
• OptiX is available on NVIDIA GPUs. It is fast, which makes it convenient in the viewport.

Leave Passes on Albedo and Normal: the denoiser uses them to tell texture detail from noise. If you prefer to denoise in the compositor, enable Denoising Data in View Layer Properties > Passes > Data and use a Denoise node, which lets you compare the raw and denoised image side by side.

The denoiser does not replace samples. Feeding it a very noisy image produces a smooth but smeared result, with wood grain, fabric and small text turning to paint. If textures look waxy, lower the threshold before touching anything else.

Why does lowering the threshold not remove all the noise?

Two common reasons. First, some pixels hit Max Samples before they reach the threshold, so the threshold no longer applies to them. Second, fireflies, the isolated white dots, come from rare and very bright light paths that adaptive sampling cannot resolve in a sensible number of samples. For those, use Light Paths > Clamping > Indirect Light, disable reflective and refractive caustics if the shot does not need them, or track down the small intense light causing them. The guide to rendering faster in Cycles covers these settings in more detail.

How do you set it on many files at once?

The same settings are exposed to Python, which helps when a shot is split across several .blend files. Run this in the Scripting workspace of each file, or from a batch script:

import bpy
cycles = bpy.context.scene.cycles
cycles.use_adaptive_sampling = True
cycles.adaptive_threshold = 0.01
cycles.adaptive_min_samples = 0
cycles.samples = 4096
cycles.use_denoising = True

Frequently asked questions

Rendering the animation on TURNA

When a scene is already well optimised and the frame count is what takes the time, the remaining lever is rendering several frames at once. TURNA does this for Blender: an add-on (Blender 4.0 to 5.2, Cycles and Eevee) sends the scene in one click, and the frames are split across 1, 2, 4 or 8 GPUs in parallel, RTX 5090 first and RTX 4090 when none is free. The add-on shows the estimated cost before anything starts. Prices start at €2.90 per hour, billed on the time actually used, with a 30-second minimum, and new accounts get €25 of free credit. A single still image is still rendered by one machine, so the gain is on animations. Tiers and worked examples are on the Blender render farm page.