Poor image quality cameras such as drones or older DSLR cameras benefit particularly well from this technique, but it does work with any camera.
It came as a bit of an epiphany to me, when I realized how big of a difference this technique makes to my drone images and old DSLR photos. The technique does come with a few drawbacks, so use it only in certain situations.
The technique is simple and mainly known from astrophotography to reduce noise in photos shot at high ISO values such as ISO 3200. The technique requires you to shoot and stack multiple images and equal out the noise, which can be done in Photoshop or other software applications. The result is cleaner images without sacrificing sharpness. I am normally very heavy-handed in my editing phase, which usually brings out a lot of noise even from photos shot at base ISO, such as ISO 100. With this technique I can effectively reduce my ISO to something like ISO 7 (yes, seven) dependent on how many photos I stack, giving me a bigger room for pushing the pixels without making the image particularly more noisy.
How to Do It
Many cameras come with a burst mode. In this case, I use an example from my DJI Mavic Platinum with a burst mode of five images but you can get seven in one push. If I want even cleaner photos, I can simply keep pushing the shutter in burst mode until I have the desired amount of photos.
After you have edited your raw files in any raw file editor such as Lightroom, Camera Raw, or any other application you need to “Load Files into Photoshop Layers.” Personally, I use Adobe Bridge as you can see in the photo below.
When you have opened your photos in Photoshop, be sure they are all perfectly aligned. If this is not the case, you will experience weird ghosting. Just select all your layers and go to Edit > Auto-Align Layers and select “Auto” as the projection. Be aware you need to crop your photo a couple of pixels as Photoshop warps, screws, and moves the photos into alignment.
When the layers are aligned you select them all and right-click and choose the function “Convert to Smart Object.”
When the separate layers are collected into one, which often takes a little processing time dependent on the amount of layers you combine, you select the new Smart Object and go to Layer > Smart Object > Stack Mode > Mean.
After another round of processing, you now have an image with greatly reduced noise. In the below images where I zoom to 100 percent you can see the comparison between the images with the effect applied and not. You will see a huge difference in how the water is interpreted, however in the basalt columns you will observe the interesting part.
In areas with movement, such as the water, there is a huge difference between the mean stacking mode and the original photo. You will have to decide yourself what works for your particular photo. If you prefer the original effect of the moving object or subject you can always do a bit of masking. Here is a full version of the photo below.
Another example where I underexposed the shadow area of the original the technique is even more visible. Here is a comparison of the straight out of camera photo and the finished edit. The difference is striking since I had to really bring up those shadows.
Zooming into the edited version (100 percent) and switching between the stacked and unstacked, the technique really proves itself. If it is hard to see on these small images, also check the 200 percent zoom below.
And the 200 percent zoom:
Mean or Median?
In all practical sense, there is no real difference between mean and median in areas without movement. Zooming all the way in the mean stacking mode averages everything out creating a softer less contrasty look, while the median stacking mode removes differences between the layers keeping the contrast.
There is only a subtly difference in the areas without movement, which you will not be able to see zoomed all the way out. The movement in the water is interpreted very differently and I prefer the softer look of the mean stacking mode. This is also a simulated long exposure effect.
You Cannot Just Copy the Same Photo
As I initially stated in the title you need to know about this technique before you start photographing. You need different photos as you cannot just copy the same photo multiple times and combine those. Doing so does not give you the difference in noise between the individual photos, which is necessary for this technique to work.
Super Duper High Quality
For even higher quality photos, you can combine burst mode and manually bracket your photos; Make a five exposure burst underexposed, five normal exposures, and five overexposed photos. Alternatively, make several AEB exposures on the drone. The result should in theory be the same, but it will require a bit more work in post-processing.
Check out the video above to see the results and a few more drawbacks where I compare some old night photos from my Canon 5D Mark III photographed at high ISO.
Is this a technique you know about? Have you already used it, or are you going to use it in the future?