In a perfect world all of our images would be noise-free and sharp. It should certainly be something that we as photographers strive for when creating an image. Unfortunately, outside of the studio we are sometimes presented with a situation that results in a less than perfect image straight out of the camera. This article will work through one such scenario and show how to deal with a noisy image that also needs some sharpening.
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For this article I will be using a recent example of a high ISO photo that also suffers from a small amount of motion blur. The techniques discussed will apply to any noisy image that also needs any level of sharpening.
First let us take a look at the image in question and how it came into being.
I was sitting in my lounge room reading a book when I saw the moon peek out from some heavy cloud cover. I hadn't taken a photo in over 4 weeks due to being in the middle of a COVID-19 lockdown, so was very keen to grab a photo. The clouds were moving very quickly and I knew I wouldn't have much time to take the shot before the moon disappeared again. So I picked up my Nikon D500 with 500mm and 1.4x converter attached and took the photo you see below. I had no time to change any camera settings.
The photo was taken handheld at ISO8000, with a shutter speed of 1/25 second. Focal length was 700mm on a cropped camera body. As you can see, not a great combination for a sharp or noise free photo!
Even printed as small as 6x4" shows significant noise. An A4 size print is quite soft and the noise overwhelms the image. Without work this image would be put right into the bin.
From the above, it is clear that in order for this image to be usable, two things need to be done:
- The noise needs to be brought under control so it doesn't distract the viewer from the image subject
- The moon needs to be sharpened in order to bring out some detail and remove the slight motion blur caused by the slow shutter speed used.
Unfortunately, both of the above fixes work against each other. Noise reduction software will easily remove image noise, but at the cost of sharpness and detail. Conversely, sharpening software will increase sharpness, but will also significantly increase the already too strong noise.
In order to get an acceptable result we will need to be very careful in how we process the image.
All photo processing software has built in controls for both noise reduction and sharpening. They can do a fantastic job when noise levels are low or moderate. However at high ISO levels, specialist third-party software will do a much better job.
The only possible exception to this is the Elite version DxO PhotoLab RAW converter. The PRIME Noise Reduction included in that software can get very close, if not equal results to third-party tools.
There are many third-party software packages out there that will do a decent job of Noise Reduction or Sharpening, but in my experience I have found that none can come even close to the results of the Topaz AI suite of tools.
If you're interested in a 30 day free trial of the Topaz software you can download them at the following links. If you decide to buy them you can get 15% off by using the code SQUAREPIXEL at checkout.
Processing The Image
Edit Exposure, Tone and Colour In The Editor of Your Choice
The first step in preparing your noisy image is to edit it as you would any other, in the editor of your choice. I generally use Adobe Lightroom Classic to process and convert my RAW files.
You do need to be mindful that any major exposure, tone and colour adjustments can make the noise in your image worse than it already is - but the aim here is to make the image into something you are happy with.
Turn off initial Noise Reduction and Sharpening
The next step involves turning off any sharpening and luminance noise reduction that your initial editor (Lightroom in my case) applies. Colour noise reduction is fine to do here. Because you will be using other software to deal with Noise Reduction and Sharpening later, it is important to turn it off at this stage so you don’t double up on the processing.
If you are using PhotoLab Elite software and plan to use the excellent PRIME noise reduction instead of a third-party option then you would keep this turned on and just turn the sharpening settings down to zero. You can also skip straight to the 'Sharpen The Image' section below if you're using PRIME in PhotoLab to reduce noise.
Apply Noise Reduction
Next you should send your processed image to your chosen noise reduction software (Topaz DeNoise in my case). Noise Reduction should always be done before any sharpening is applied.
To show why noise reduction should happen first, take a look at the example photos below. They have been cropped to 100% to show the differences more easily.
First is the original unprocessed image. Next is the same image that has been sharpened first and then had noise reduction applied. Finally, the third image had noise reduction applied first and was then sharpened.
The image that had the sharpening applied first has much less detail, has ugly blotches and is overall very ‘mushy’. The image that had noise reduction applied first is much more detailed and doesn’t suffer from the artifacts or muddiness.
When you sharpen a noisy image, the sharpening software can't tell the difference between the image detail and the noise. As a result, the noise in the image is sharpened which just exacerbates the problem. The noise reduction software then has a much harder job in trying to determine which parts of the image are noise and which is detail, resulting in a much softer image overall.
The image below shows the effects of sharpening a noisy image in Topaz Sharpen AI without doing noise reduction first. On the left is the original, noisy image and on the right is the sharpened output.
Compare that to when noise reduction is applied first. The image below shows the DeNoised image on the left and the sharpened image on the right.
Sharpen The Image
Once the noise in the image has been removed you can then sharpen the image in the sharpening software of your choice.
In the case of my example image I am using Topaz Sharpen AI to correct some motion blur due to me using a slow shutter speed in combination with a long lens. If your image doesn’t require any ‘rescuing’ you may be able to use the basic sharpening tools available in your image editor.
After the careful application of Noise Reduction and Sharpening, the original, virtually unusable image used as an example is now something that can be printed to a decent size.
As mentioned at the start of this article, the original image showed significant noise even at a tiny 6x4" print. At A4 size the slight motion blur and noise made for a very soft image that was destined for the bin.
By applying Noise Reduction first and then Sharpening I was able to print the image at A3 size with no evidence of noise or motion blur and a decent amount of detail in the moon. Certainly a result that anyone not closely looking for image flaws (ie, most non-photographers) would be happy with.
When it comes to sharpening noisy images, much more care needs to be taken than when dealing with noise-free images. Using specialist third-party software to do the job can yield much better results than relying on the tools provided in most of the major image editors.
Sharpening a noisy image should follow the steps:
- Edit exposure, colour and tone in your normal way - making sure sharpening and noise reduction are turned off
- Remove the noise in the image
- Sharpen the image
Using Topaz AI Software I was able to turn an image that I couldn't realistically print at ANY size into something that looks great at A3 and would probably even print larger with no problems as viewing distances get further away.