One of my favorite photography technique that I tend to use the most is doing long exposures photography. However, a major issue I always run into on all my long exposure pictures is hot pixels.
Sometimes, when you zoom in and inspect your image with a 1 to 1 ratio, you will sometimes see red or green or blue dots scattered all over the images. This is called hot pixels.
What is Hot Pixels?
Ok, the first thing to note is that this is not a defect in your digital camera, this is an expected behavior. You will often find hot pixels in your images during long exposures. These are caused by an electrical discharge that leaks into the sensors or when the sensor overheats during a long exposure shot. The level of the hot pixel you would encounter depends highly on the external environment.
These hot pixels might not be obvious to the naked eye. But, a photographer can see it too clearly, and it does bother us. It also becomes an issue when you enlarge the image and make prints. We really do not want that reducing the quality of our image. What if you knew how to get rid of them? That would be a really good tip to learn, I am sure.
Before I learned this technique, I used to manually clean up all the hot pixels using the spot healing brush in Lightroom or Photoshop This was a time consuming and at times, a very frustrating process. I then started doing some research to try to find an easier way to deal with hot pixels.
In my research, I came to know that there is no permanent fix to get rid of the hot pixels. However, there are a few ways we could try to minimize the impact that these hot pixels have on your image, and make them manageable.
These 4 methods are not all foolproof and might not all work for all your long exposure images.
You may find success in one of these methods or none of them to try to get rid of those pesky hot pixels. However, they certainly are worth a try and would save you a lot of time. Therefore, it definitely is worth a try.
Here are the 4 methods you could try to get rid of hot pixels from your photographs.
Method 1 – Removing Hot Pixels In Your Camera
We could first try to avoid hot pixels coming on our images by working on some camera based settings. Here are the steps you could follow to try this out.
- Remove the lens and put your camera cap onto the camera.
- Turn your camera on and go to the Sensor Cleaning menu.
- Perform a cleaning by facing the camera downward. This should do a mirror lock up and remap the sensor.
- Leave it in this setting for thirty seconds to a minute.
- Turn your camera off and turn it back on to see if the problem is fixed.
The above method seems to have helped a bit but did not fully resolve the issue in my Sony A7R mirrorless camera. I am yet to test this method of removing hot pixels from my Nikon System.
Method 2 – Reduce Hot Pixels Using Noise Reduction While Post Processing
If the fix on the camera doesn’t work out, there is something you could do on the image while post-processing to minimize the effects of the hot pixels.
This was one of the techniques that I discovered on the Adobe Forum while on my quest to remove hot pixels faster. Man! I sure wish I knew the existence of this method earlier – it would have saved me a boatload of time.
Ok, here the technique. Firstly, you need to be aware that this method involves a lot of trial and error. You would need to keep trying over and over until you find the right range of ratios that work for your image. That said, this also means that while it worked for me, it may or may not work perfectly for you. But I definitely feel like it is worth a try.
- Open your image in Adobe Photoshop
- From the menu bar, go to Filter -> Noise -> Dust & Scratch menu.
- Set the radius between 1 and 4 pixels (Do not use a bigger radius – this would result in you seeing some artifacts in the image).
- Set the Threshold between 16 to 25 level (this is a good range where you would see the effect without the added artifacts on the image).
- Hit OK and that’s it.
Now you will see the hot pixels magically disappear.
Method 3 – Long Exposure Noise Reduction Through Camera Settings
Turn the Long Exposure Noise Reduction settings On in the Camera Settings
This is one of the most effective ways to resolve the hot pixel problem. However, there is a downside to this technique – it doubles the exposure time you would use when you take a picture. This is because when you are taking a long exposure shot, it would take the exact amount of time to take another dark image exposure. For instance, if you are taking a 5-minute exposure image, the camera would need an extra 5 minutes to take a dark image exposure to subtract the hot pixels.
Method 4 – Blend Image Using Dark Exposure
This approach involves taking the image twice – once as usual and once under dark exposure.
- We will take the dark exposure image first. Set the camera up with the settings that you desire, but first put the lens cap on.
- Take the dark exposure with that setting.
- Remove the lens cap and take the long exposure as you had planned to. You can choose to change the long exposure settings at this point if needed.
- Even if you had altered the settings for the regular long exposure image, you don’t have to redo the dark exposure image. You can use what you had initially taken.
- While post-processing with Adobe Lightroom, you edit the long exposure image as you wish to. Then apply this same setting to the dark exposure image.
- Then open both the dark image and the normal image as layers in Photoshop with the dark image as the top layer.
- Change the blending mode to subtract.
This should fix the hot pixels issue on your long exposure image.
As we had mentioned at the beginning of this post, these methods are not clear fixes for the hot pixel issue. Some of these methods would work better on some images than others. It all depends on your image, how they were taken and many other factors.
For instance, Method 2 works a lot of the times for me, but NEVER for any of my astrophotography images. I don’t quite know why one method works better on one kind of photograph than the other 3.
However, these methods are easy to try out and takes very little time (especially when compared to what I used to do before I discovered any of these techniques). So they really are worth a try! If you manage to fix the hot pixels issue with any one of these methods – then that is time well spent.
As a photographer, I can understand how frustrating those hot pixels can be. I hope that the above techniques can help you get rid of these pixels and make better pictures.
If you have another technique that works as well, please feel free to share it on the comment section below.