Long exposure shot of Orion over the Natural Bridge in Yoho National Park - Monika Deviat
Final edited image where hot pixel removal was required.

Hot Pixels will generally appear when shooting long exposures. The hot pixels are bright spots that may show up in your image when taking a long exposure shot, especially at higher ISO values. If only a few appear in your image, you can clone them out quickly. However, if you get a lot of spots, going in and cloning the spots out can be a tedious and time-consuming process.

Hot Pixels in a long exposure shot - Monika Deviat
A large number of hot pixels from a long exposure. 140s at ISO 3200.

There are a few ways to deal with hot pixels:

  • Dark Frame Subtraction: This method minimizes image noise by subtracting a second exposure captured with the sensor in the dark (with the lens cap on for example). The position of the hot pixels would be fixed between the two frames. This method takes more time in the field, and you have to remember to do it.
  • Adjust settings: Lowering ISO or decreasing exposure time could minimize the number of hot pixels that appear in an image. However, this may not give you the desired final result.
  • Post Processing Techniques: This is what I will go over in this blog. This technique requires Photoshop.

Tutorial Steps

Open your image in Photoshop. The image I am using was taken in October 2018. It was relatively warm for a fall night in the Rockies. This shot is my foreground image. A second image was taken for the sky at a shorter exposure to capture Orion and minimize star trails.

Tutorial - Removing Hot Pixels in Photoshop - Monika Deviat
Load images to Photoshop

Duplicate the background layer, Command/Ctrl+J. You can rename it however you want.

Tutorial - Removing Hot Pixels in Photoshop, Copy Layer - Monika Deviat
Duplicate background layer.
Tutorial - Removing hot pixels in Photoshop, zoom in - Monika Deviat
Zooming in on background layer to see hot pixels.

Select Filter -> Noise -> Dust & Scratches

Tutorial - Removing hot pixels in photoshop, dust and scratches - Monika Deviat
Use dust & scratches under noise.

The value chosen for Radius should be small, as the noise we want to remove is minimal. I have decided on 2 with a threshold of 5. You can play around with the values and converge on parameters that eliminate all the noise but minimize any effect on the rest of the image.

Tutorial - Removing hot pixels in photoshop, noise parameters - Monika Deviat
Hot pixels are removed.
Tutorial - Removing hot pixels in photoshop, noise parameters - Monika Deviat
Choosing values that are too large affects the whole image and. You can play around with the settings to see how everything is affected.

Once you apply the Dust & Scratches filter, go to the layer panel and change the blending mode of the layer to Darken. The darken mode will compare the pixels between the background layer and the copy and replace the lighter colours with darker colours.

Tutorial - Removing hot pixels in photoshop, darken mode - Monika Deviat
Changing blending mode to darken on the layer with noise filter.
Tutorial - Removing hot pixels in photoshop, blending
Hot pixels are gone and there has been minimal change to the rest of image.

If you’d like to learn more about night photography and get out in the field, I have a variety of workshops available, as well as private photography tours.