Raw SmithBlog
How to reduce noise in high-ISO RAW photos on iPhone, iPad and Mac
To reduce noise in a high-ISO RAW photo, start before you edit: expose as brightly as you safely can. Then, in this order, set exposure and white balance, remove colour noise, add only as much luminance noise reduction as the photo needs, and sharpen last. On iOS 27 and macOS 27, Apple's machine-learning RAW 9 decoder does most of this work for supported cameras.
Where the noise comes from
Most of the noise in a photo isn't caused by the ISO setting itself. It comes from too little light. Light arrives at the sensor as individual photons, and in dark areas so few arrive that the count varies randomly from pixel to pixel. That randomness is the grain you see. Raising ISO amplifies the signal so the picture is bright enough to view, and the grain is amplified with it.
That has a practical consequence: brightening a dark photo afterwards is what makes noise ugly. Every stop of exposure you add in the editor brightens the noise along with the picture, and it shows most in the shadows. So the first noise tool is the camera.
Expose as brightly as you safely can
Give the sensor as much light as the scene allows: the widest aperture you're happy with, the slowest shutter speed you can hold or support on a tripod, and then the ISO that makes the exposure bright. Aim for a histogram that sits to the right without clipping the highlights you care about. This is often called "exposing to the right".
A brighter exposure at ISO 6400 is usually cleaner than a dark one at ISO 1600 lifted two stops later. Many modern sensors are close to "ISO-invariant" over part of their range, meaning the two come out similar, but few cameras reward underexposure. If in doubt, expose brighter and pull it down in the edit.
Luminance noise and colour noise
| Luminance noise | Colour noise | |
|---|---|---|
| What it looks like | Fine grain in brightness, like film grain or sand | Red, green and magenta blotches, mostly in shadows |
| How bad it looks | Often acceptable in moderation | Almost always ugly |
| Cost of removing it | Fine detail and texture go with it | Very little |
| How much to use | As little as works | Enough to make the blotches go |
The rule of thumb is to take out nearly all the colour noise and only some of the luminance noise. A little fine grain reads as texture. A smeared, plastic look, where skin, foliage and stone all turn to wax, reads as a bad edit.
Noise reduction in the RAW decode
The cleanest place to reduce noise is while the RAW is being developed, before the picture is made. On Apple devices, the system RAW decoder has its own noise controls, tuned for each camera, and editors built on it can expose them.
In Raw Smith they're in the Detail panel, and each starts at the decoder's default for your camera:
| Noise Reduction | Luminance noise. Raise it for grain; watch fine texture as you go. |
|---|---|
| Color Noise | Colour blotches. Raise it until they're gone. |
| Detail | Brings out fine detail. More of it also brings back some grain, so balance it against Noise Reduction. |
| Moiré | False colour patterns on fine repeating detail such as fabric. |
| Sharpening | Sharpening in the decode. |
| Edge Contrast | Local contrast along edges. |
You only see the ones your camera's decoder supports. Because they happen in the decode, their effect shows once the photo settles after you let go of a slider. Zoom to 100% (double-tap the photo, or use the 100% / Fit button) on a shadow area before judging them. If the original is still in iCloud, download it first: the Detail panel works on the RAW.
Try Apple's RAW 9 decoder
On iOS 27, iPadOS 27 and macOS 27, Apple added a new decoder, RAW 9, that uses a machine-learning model to demosaic and reduce noise in one step. Apple showed it cleaning up very high-ISO files while keeping more detail than before (WWDC 2026 session). It works on photos you already have, for cameras on Apple's RAW 9 list.
In Raw Smith, turn on Enhanced below the sliders in the Detail panel. The switch only appears where your system offers RAW 9 for that file. With it on, colour noise, detail and moiré are handled by the model, so those three sliders go away; Noise Reduction, Sharpening and Edge Contrast stay. Start with Noise Reduction low: the model has already done much of the work. What Apple's Enhanced decoder does explains it in full.
Reduce noise only where it shows
Noise is rarely even across a photo. It's worst in smooth, dark areas: a night sky, a shadowed wall, the background of an indoor portrait. Those are also the areas where losing fine detail costs least. The subject, with its texture and edges, often needs less.
So keep the global noise reduction moderate and add more where it's needed with a mask. In Raw Smith, open the Masks tab, tap New Mask and select the area: Sky or Background, a Linear gradient, a Luminance range set to the darkest tones, or a Brush. Then raise Noise in the mask's Detail group. You can go the other way too: a Subject mask with a little Sharpness.
The mask's Noise works on the developed image rather than in the decode, so it's an extra layer on top of the Detail panel, not a replacement.
The sharpening trade-off
Sharpening and noise reduction pull in opposite directions. Sharpening raises contrast at small scales, and to an algorithm, grain is small-scale contrast. A heavily sharpened high-ISO photo shows crunchy, brittle noise.
- Set noise reduction first, then add sharpening until edges look crisp at 100% and stop before the grain does.
- Texture and Clarity in the Effects panel sharpen too, in effect. Keep them low on noisy photos, or apply them through a mask that avoids the smooth areas.
- Lifting Shadows and Blacks reveals noise. If the deep shadows are noisy, leaving them a little darker is often the better photo.
Export at the size you need
Noise you see at 100% on a 45-megapixel file often vanishes at the size people actually see the photo. Downsizing averages many pixels into one, which averages the noise away. A photo that needs heavy noise reduction for a large print may need very little for Instagram.
So judge at the output size. In Raw Smith's export sheet, Size offers Full Resolution or Web / Social (2048px). On the Mac, batch export adds Resize To sizes and Output Sharpening; for noisy photos, try Low or None (see the export guide).
How Raw Smith fits
Raw Smith is a RAW editor and library for iPhone, iPad and Mac, built on Apple's system decoder. For noise it gives you the decoder's own controls in the Detail panel, the Enhanced RAW 9 switch where the system offers it, and per-mask noise reduction and sharpening. To find the photos that need it, make a smart album with the rule ISO is at least 3200.
What it doesn't do: there's no separate AI denoise that writes a new DNG, and it doesn't stack multiple exposures to average noise away. If you need those, a dedicated tool such as DxO PureRAW or a stacking app is the answer; Raw Smith edits the RAW you give it. It's a free download with a free tier and a 14-day trial; Pro is a one-time purchase or a yearly plan. Try it in the public beta on TestFlight.
Questions
What's the difference between luminance and colour noise?
Luminance noise is grain in brightness, like sand over the picture. Colour noise is blotches of red, green and magenta, mostly in the shadows. Colour noise can be removed almost for free; luminance noise reduction always costs some fine detail.
Should I reduce noise before or after other edits?
Set exposure and white balance first, because lifting the shadows makes noise worse and changes how much you need. Then set noise reduction, and come back to sharpening last.
Does shooting at a lower ISO always mean less noise?
Not if it leaves the photo dark. A well-exposed photo at a higher ISO is usually cleaner than an underexposed one at a low ISO brightened later, because noise depends mostly on how much light reached the sensor.
Is Apple's RAW 9 better at noise than the old decoder?
For high-ISO photos, usually much better. It removes noise while it reconstructs detail, so it keeps more texture. It works on iOS 27, iPadOS 27 and macOS 27 for cameras on Apple's RAW 9 list.
Does resizing a photo reduce noise?
It makes noise less visible. Shrinking a 24-megapixel photo to 2048 pixels averages many pixels into one, so grain that was obvious at 100% mostly disappears.