In long exposure and low light photography you’re faced with noise and potentially “hot pixels“. While noise is frustrating, hot pixels are devastating. If they aren’t removed, the image is severely affected for any close viewing or printing. Traditional noise reduction techniques aren’t designed to fix hot pixels and cloning potentially thousands of bad pixels individually from an image is no one’s idea of a good time. Thankfully, there’s a must simpler fix and you’ll learn all about it in this week’s tutorial.
To remove hot pixels with the Dust & Scratches Filter:
- Duplicate your layer (or image via ctrl/cmd-alt/option-shift-E) or convert it to a Smart Object to work non-destructively.
- Go to Filter / Noise / Dust & Scratches.
- Zoom in to at least 100% and start with both sliders to the far left.
- Increase the radius slider by one at a time until you find the smallest number that gets rid of most or all hot pixels. Do no go above this, as you will lose only lose image detail. This is typically 2-4.
- Increase the threshold slider until you find the largest number that does not re-introduce the hot pixels. This slider helps restore detail and grain in the image. Typically 5-10 is a good number, but you may go higher. Click OK when done.
- This filter is safe to apply to color nearly everywhere, but needs to be applied judiciously to the luminosity in areas of detail. So use the following two-prong fix:
- Create a duplicate of the fix and set one copy to “color” blend mode.
- For the “normal” blend mode version, add a black layer mask and then paint white to reveal the full fix as needed. Use selections to help make the painting faster and more precise.
- There may be a few stubborn hot pixels that aren’t removed by the filter. Just create a blank new layer and use the spot healing brush (set to sample all layers) to finish.
If you’re working on night images, this is also a great way to fix the foreground. If you’re trying to clean up a starry sky, you might wish to apply this more selectively with a brush or using color options in Lumenzia in order to avoid applying this filter on stars (since it will suppress them).