The colour speckle goes, your grain stays. Only the colour of your photo is smoothed; its brightness, where the film grain lives, is left as it was.
Find a dark frame, open Details, raise the dose. Chroma Denoise is already on when your photo opens, at a light dose.
Find a dark, thin frame. That is where colour speckle shows. Open its roll with Open Folder… in the File menu (⌘O, or Ctrl+O on Windows).
Open the Details tab. Chroma Denoise sits between sharpening and texture.
Raise the dose. Amount, then Radius, looking at the dark areas of your photo, where the speckle shows most.
Only the colour is smoothed. Grain is the texture of your film itself: dye clouds on a colour negative, silver on black and white. It lives in the brightness of each pixel. The coloured speckle is noise from the scan, made louder by the conversion, as the research below explains. So only the colour is smoothed.
One row of pixels, illustrative: the mean step from one pixel to the next
| Line | Before | After |
|---|---|---|
| Brightness, where the grain lives | 0.037 | 0.037 |
| Colour, where the speckle lives | 0.075 | 0.003 |
Cleaner colour, the same grain, the same file. Chroma Denoise works on your converted photo, after the inversion.
At zero, it is off. Either slider at zero turns the stage off. On a contact sheet it is off, its settings kept.
Made for colour. A monochrome photo has its tones in brightness alone: its Details tab holds sharpening and texture.
The same dose in your file. Radius is counted in full-resolution pixels, the ones the export gets, whatever size you look at.
Noise, grain and night frames. The short answers first, then the detail.
Open the Details tab: Chroma Denoise is already on, at a light dose. Raise Amount, then Radius, while looking at the dark areas of your photo, where the speckle shows most.
Your grain stays as it was. Your photo is split into brightness and colour, and only the colour is smoothed: the brightness of every pixel, where the grain lives, comes back as it was, at any dose.
Yes, at a light dose: Amount starts at 20% and Radius at 4.0 px. Either one at zero turns it off. It is off on a contact sheet, whose frames are reduced copies, and the settings are kept for when a photograph takes them.
Because a thin negative, underexposed, pushed or shot at night, gives the scan little to read, and the strong gains that take the orange mask off turn that into coloured speckle in the shadows. That is where to look while you raise the dose.
Until large flat areas start to lose their colour variation, since only the colour is smoothed. Your grain stays as it was at every dose, so the colour of flat areas is what tells you to stop.
Yes. It is counted in full-resolution pixels, the ones the export gets, whatever size you look at your photo.
A black and white photo carries its tones in brightness alone, so its Details tab holds sharpening and texture, and Chroma Denoise appears on your colour photos.
See all sixteen conversions, real photographs converted in Open Negative Initiative, each with its raw scan.
From your scan to your export. One page per feature.
Add your folder, prepare the roll once, export. Free, and nothing else to install.
Snow night. Kodak Gold, converted in Open Negative Initiative.
Your negative, your light, your sensor. Knowing what makes colour noise tells you which frames need more of the dose, and how to scan your next roll with less of it.
A colour negative is orange because of a mask built into the film to correct its dyes. Under it, the blue of your scan gets far less light than the red, so it is recorded with less signal and proportionally more noise. The conversion takes the mask off and inverts, which means strong gains on the weaker channels: their noise rises with them, and shows as specks of colour.
An underexposed or pushed frame, or one shot at night, leaves little density on the film in its shadows. To draw a full range of tones out of so little, the conversion stretches small differences, and the scan's noise is stretched with them. That is why the speckle gathers in the dark areas of these frames, and why they are the ones to check first.
| You scan with | Set | What it gives your scan |
|---|---|---|
| A camera | Its base ISO | The cleanest signal its sensor records |
| A camera | An exposure that puts the brightest part of the negative just under clipping | As much light in every channel as the sensor can take, the starved blue included |
| A film scanner | Its native resolution | Every pixel read by the sensor itself, none made up between two readings |
| A film scanner | Multi-sampling, if it offers it | Each pixel read several times and averaged, so the random noise drops |
With a camera, scan at its base ISO and expose so the brightest part of the negative sits just under clipping: every channel then gets as much light as the sensor can take. With a film scanner, scan at its native resolution, and use multi-sampling if it offers it. A cleaner scan needs a lighter dose here, and keeps more fine colour.
| What you see at 150 or 200 % | What to move |
|---|---|
| Fine specks of colour in flat dark areas | Raise Amount until they melt into the tone around them |
| Colour noise in larger blotches | Raise Radius |
| Large flat areas losing their colour variation | Bring Amount back down |
| Your grain | Nothing: it stays as it was, at every dose |
The Details tab opens with a loupe that shows your photo at 150 %, and at 200 % with a click on its ratio: speckle that hides at screen size shows there. Look at flat dark areas, a night sky, a shadowed wall, skin in low light. Raise Amount until the specks melt into the tone around them, and Radius when the speckle comes in larger blotches.
Each pixel is split into its brightness, a weighted sum of its red, green and blue, and its colour, what is left once that brightness is taken off: its luma and chroma. Only the colour is blurred, with a Gaussian blur over the radius you set and at the amount you set; the brightness is put back as it was. Sharpening and texture are separate controls.
Amount sets how far each pixel's colour moves toward the smoothed one: at the default 20 %, a fifth of the way; at 100 %, all of it. Radius sets how wide a neighbourhood the smoothed colour is drawn from.
| Block | What it works on | Its sliders |
|---|---|---|
| Sharpening | The brightness of your picture, at its edges | Amount, Radius, Halo limit |
| Chroma Denoise | The colour of each pixel, its brightness put back as it was | Amount, Radius |
| Texture | Contrast at the scale of hair and fabric, leaving grain and overall tone alone | Texture |
After the inversion, on your converted photo, in the same pass as sharpening: brightness and colour there are those of your picture, the ones you see, so the dose you judge on screen is the dose that acts. The inversion comes first.