Red, Blue, Green Pixels

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2021-08-03 17:33:33

I am trying to edit a photo using the lighten and darken tools but red, blue and green pixels always pop up every time. What can I do to fix this?
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2021-08-24 14:00:02

Hey Judith! That's a known issue that sometimes can occur with images converted from RAWs. Any chance that's the case in your situation as well?
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2021-12-14 09:29:59

I experience this issue as well. It happens when editing RAW files from Canon EOS R5. I'm using Pixelmator Pro 2.3.1 on an M1 MacBook Pro (2020) on macOS Monterey. It also happens on Big Sur.

Steps to reproduce:
1. Open a RAW file.
2. Select the Darken or Lighten tool.
3. Convert the layer to pixels.
4. Use the tool. Red pixels appear, esp. in dark areas.

Example RAW file:
http://szafranek.net/files/tmp/8119_2021_11_27.CR3

Resulting image with red pixels is attached: Image


Best,
Chris
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2021-12-14 16:04:05

I think this issue has nothing to do with Darken or Lighten tools. The colorful RGB dots must be harsh digital noise or hot pixels, usually present in high-ISO shots like the one Braun has presented (their shot was made at ISO 8000). I guess this issue has to do with Apple RAW conversion engine, which Pixelmator relies on. Chances are, Apple RAW conversion engine is unable to properly remove digital noise from your RAWs. And when you apply Lighten tool afterwards, you just accentuate the noise and make it more prominent.

To check this, I have developed Braun's photo in DxO Photolab 5 with and without denoising.

Here'a a crop of this RAW, developed in DxO with denoise ON:
Image
As you can see, everythings's clean and smooth, no colorful dots whatsoever.

And here's the same crop, developed in DxO with denoise OFF. The digital noise is already prominent:
Image

Now let's export both photos as PNG, open them in Pixelmator, paint with Lighten tool over them a bunch of times and see what happens.
Here's the denoised one. As you can see, no colorful dots whatsoever, even after painting with Lighten tool four times:
Image
And here's the one that hadn't been denoised, after the same treatment with the Lighten tool:
Image
As you can see, RGB dots are all over the painted area.

Bottomline: to avoid RGB dots, develop your RAWs in an application with a quality denoiser.