As a photographer y’all are probably confronted every now and then with unacceptably high noise levels. This may occur when using extremely loftier ISO levels, or perhaps when lifting shadows too much in post processing. You can try to reduce noise by one or ii sliders in Photoshop, Lightroom, or like software, or by stacking a couple of photos.
Did you know some photographers were deliberately trying to increase the amount of noise in the analog days of photography? Of course, it wasn’t called noise in those days, but grain. Yet, those photographers loved the grainy feel of their photos. They exposed a 400 ASA picture equally were it a 1,600 ASA and corrected the underexposure during the development of their films, thus introducing an increased amount of visible grain. I used this method to get faster shutter speeds for my concert photography and took the grain for granted.
Today, most cameras take amazing high ISO capabilities. If your exposure is correct, so you don’t accept to recover whatever underexposed parts, it is virtually incommunicable to see racket at ISO ane,600, ISO three,200, or even ISO half dozen,400 with some cameras. Maybe, if you enlarge your image on screen up to 100%, some noise may be visible. What you find to be an acceptable corporeality of noise is very personal. But sometimes you might desire to take absolutely no noise whatsoever. Using a skilful noise cancellation program is not e’er the solution, and removing noise may lead to loss in particular, just like the sample below.
Since I too use a drone for my photography, I am confronted again with higher dissonance levels compared to my full frame DSLR cameras. The 1” sensor of the DJI Mavic Pro 2 produces noise in situations where a decent total frame camera wouldn’t. Of class, the small sensor size is largely responsible for this, only that is not the point. No matter what the reason may be; the noise levels are increasing rapidly when post-processing the DNG files up to extremes. It is influencing the epitome quality a lot, and noise reduction will merely lead to an unacceptable loss in detail. Unless you use stacking multiple images for racket cancellation. A technique oft used past astrophotographers.
The stacking technique makes use of the random nature of noise. By making a series of images without moving the photographic camera, every unmarried epitome will have a slightly unlike noise pattern. When combining these images in a smart way, it is possible to cancel out the noise, without loss of particular. Because we make use of the random dissonance in a series of images, it may be articulate this technique does not work with a series of copied images.
The downside of this method is the limited utilise of the technique. It needs a stationary scenery, without (a lot) of move, and you demand to shoot on tripod – although it might be possible to shoot without it in high speed mode and aligning the images afterwards. It all depends on the situation.
There are a few things to continue in mind; moving objects will get fuzzy, or disappear completely in the end outcome. Also lens baloney corrections tin give unexpected results, just like the stacking of the star trail images I showed in a previous article here on Fstoppers. And y’all also need software that is able to work with layers, just like Photoshop.
This technique tin besides exist used for other purposes. I already mentioned astrophotography and star trails, only also super resolution, deliberate removing moving subjects in a scenery, and long exposure simulation use a similar technique.
Let me show how stacking images works and how it affects noise levels. I utilize Lightroom and Photoshop for this, and I selected a photograph I made with my drone during the late twilight. I did set my exposure settings for the brightest spot in the epitome, to prevent blown out highlights, and ended up with ISO 100, f/ii,eight, and a shutter speed of ¼ of a 2d. I made a burst of five sequential images.
After I imported all images in Lightroom, I edited i of the five images to my liking, making use of the dynamic range of the drone camera. I copied all settings to the remaining four images. I made sure to fix sharpening and racket reduction to zilch, and disable all lens distortion settings. Next, I have transferred all images equally layers into Photoshop.
At present I take all images in Photoshop, every bit layers on top of each other. First, I must be sure the images are perfectly aligned. If I would apply a photographic camera on tripod, this step is probably non necessary, just a hovering drone may cause a slight misalignment, particularly when there is a lot of air current. You tin can align the images automatically past choosing [edit/auto-align] in the menu. Brand sure you disable the option vignette removal and geometric distortion and permit Photoshop practise an automatic projection.
Check if all layers are perfectly aligned. If i prototype may still exist misaligned, delete that layer. But remember, the more images y’all stack, the better the results.
If everything is to your liking, select all layers over again and transform it into a smart object. Y’all tin can find this option in the menu [Layer/Smart Objects/Catechumen to Smart Object]. Depending on the size of your prototype, and number of layers, this may take a while. When the smart object is made, you can stack the layers in the smart object with the selection Median, that can be found in the card [Layers/Smart Object/Stack Way/Median].
After the stacking is done, you might want to rasterize the image, and then information technology becomes a normal layer again. This volition reduce the file size. After this concluding step I am prepare to save the file, which is then automatically added to the Lightroom catalog.
That’s it. You successfully stacked the images and reduced the noise levels without loss of detail. But look at the event and compare it with one of the original images.
The more images you stack, the better the result will be. I find five images from the drone the minimum, and rather have ten images, which is easy to reach, of course. This stacking method works not just for drone footage, but as well for photos fabricated past whatsoever other camera, as long every bit there are no moving subjects in the frame. Even the slightest moving tree branches, or leaves, may crusade foreign results. So there is a limitation to the method.
If you don’t accept the possibility to work with smart objects, yous can manually accommodate the opacity of the layers to get the aforementioned issue. The first layer should exist at 100%, the side by side one to a higher place at l%. The third layer must have 33% opacity, the 4th 25%. The fifth layer must be set up at twenty%.
Have you ever used this method for removing noise? What is your experience with it? And if y’all haven’t used it, would y’all consider trying it? I would beloved to read about it in the comments.
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