Monday, May 31, 2021

How to Reduce Noise in Raw Photos Using DxO PureRaw

DxO PureRAW claims to open your RAW photographs up to new possibilities. Now available as a standalone app, it’s designed to act as a first step in your editing process so that you can start with the best base possible.

The software exports a new .dng raw file after you’ve run one of its filters, retaining all your RAW information plus the noise reduction, ready to continue your workflow in your usual editing image suite. More than just a noise reduction tool, DxO claims:

‘PureRAW uses smart technology to fix the seven problems that affect all RAW files: demosaicing, denoising, moiré, distortion, chromatic aberrations, unwanted vignetting, and a lack of sharpness.’

It does this with ‘convolutional neural networks’ which have developed advanced analysis from the millions of images and thousands of cameras in DxO's databases.

noisy image examplenoisy image examplenoisy image example
The image I'll be using

This is the image I’ll use to demo PureRaw. It was taken in a dark museum with the ISO cranked up to 6400. I’ve lightened this image in Adobe Camera Raw so you can see the noise more easily, but in the demonstration the image doesn’t retain the sidecar data from ACR, so it’ll look much darker; hopefully you’ll still see the difference in the noise reduction. I’ll pop it back into ACR at the end with the same settings so you can see the true before/after.

1. Open PureRaw

Let's get into it.

PureRaw opened upPureRaw opened upPureRaw opened up
PureRaw opened up

This is how the software looks when you first open it. You can click on the screen to add your photos, or select and drop in as many as you like, to get started.

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Optics options

If it’s your first time loading in a photograph then you’ll be asked if you want to download the modules to apply optics corrections to your specific equipment. Whether you do this or not is up to you and will probably depend on your upcoming workflow. You may prefer to apply these elsewhere.

I’ve installed them for the purposes of the demo so that I’m starting with the best possible base to show you the results, but if I was intending to open the image in Adobe Camera Raw to make edits after running it through PureRaw then I’d stick to using the profile corrections there instead.

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Thumbnail of your image(s)

Once you’ve done that you’ll see your image(s) appear as a thumbnail.

2. Run the PureRaw Filters

Now we can start the de-noising process.

Processing optionsProcessing optionsProcessing options
Processing options

You’ll see three methods: HQ, PRIME and DeepPRIME, here’s a rundown of each:

  • HQ: this is a lighter touch noise remover, designed for images that were taken in regular lighting conditions. Note: My computer estimated this would take 26 seconds.
  • PRIME: a medium option that takes longer to run than HQ, but claims to work better for images taken in low light. Note: My computer estimated this would take around 1 minute.
  • DeepPRIME: the strongest noise reduction, this option claims to yield ‘breath-taking’ results but takes a while to run and requires a lot of processing power. Note: My computer estimated this would take around 2 minutes, which didn't seem unreasonable for 'breath-taking results.'

It’s disappointing not to get a preview image when highlighting each option, as you do with ACR’s new Super Resolution tool, but comparably, it's very quick to run so it doesn't matter too much.

Processing finishedProcessing finishedProcessing finished
Processing finished

When it’s finished running the tool you’ll get the option of exporting it straight to your usual editing software, or viewing the results directly in PureRaw with a before/after. I ran each filter on the same image, here are the results:

HQ

HQ processingHQ processingHQ processing
HQ processing

PRIME

Prime processingPrime processingPrime processing
PRIME processing

DeepPRIME

DeepPRIME processingDeepPRIME processingDeepPRIME processing
DeepPRIME processing

What These Results Actually Mean...

It's very difficult in the previews to see the real differences, and for this reason it would have been nice if PureRaw also had the option to do some basic edits, because quite reasonably many of the images that will be noisy and in need of correction are those taken in low light conditions. Here's the result after lightening it in ACR:

After DeepPRIME plus lightening in ACRAfter DeepPRIME plus lightening in ACRAfter DeepPRIME plus lightening in ACR
After DeepPRIME plus lightening in ACR

And so you don't have to scroll back up, here's a reminder of the before image with the exact same ACR settings:

Before imageBefore imageBefore image
Before image

Certainly a big difference and the result isn't overly soft, though it definitely has softened some. Here are two slices of image taken at 100%.

Before DeepPRIME

Image taken at 100% before DeepPRIME is appliedImage taken at 100% before DeepPRIME is appliedImage taken at 100% before DeepPRIME is applied
Image taken at 100% before DeepPRIME is applied

After DeepPRIME

Image taken at 100% after DeepPrime has been appliedImage taken at 100% after DeepPrime has been appliedImage taken at 100% after DeepPrime has been applied
Image taken at 100% after DeepPrime has been applied

The result looks more impressive up close and 100% zoom doesn't usually take any prisoners, so if there are faults to be found then looking up this close will usually find them, but it's pretty good. Definitely softer, but all that has been done to the photo other than DeepPRIME is to lighten it, so there are still sharpening and texture options that can increase that detail without bringing the noise back into the image.

To open the photo into your usual editing software after you’ve viewed the results, just right-click and choose that option. If it’s the first time you've used the software, you’ll have to navigate to where your editing program is installed.

Can This be Achieved Elsewhere?

Before and After Adjustment in Adobe Camera RAWBefore and After Adjustment in Adobe Camera RAWBefore and After Adjustment in Adobe Camera RAW
Before and After Adjustment in Adobe Camera RAW

What I was most curious about was whether I could achieve the same result right in Adobe Camera Raw. Looking at the before/after above it's tempting to say yes, but this is only at about 15% magnification. Looking at 100% tells another story. 

After noise reduction in Adobe Camera Raw (100% magnification)After noise reduction in Adobe Camera Raw (100% magnification)After noise reduction in Adobe Camera Raw (100% magnification)
After noise reduction in Adobe Camera Raw (100% magnification)

The noise is mostly gone but the image is a lot softer than it was after DeepPRIME, and I'm left with a purple haze that would need correction elsewhere. If you look closely there are also one or two leftover artefacts that appear in a similar way to hot pixels, little squares of colour.

Conclusion

I put DxO PureRaw through its paces by using an image that in most cases wouldn’t be salvageable, and I think this is the key. While DxO recommends running all your RAW images through it, it’s actually better suited to those cases where you really need it. Most cameras and associated editing software suites are capable of a decent level of noise removal, certainly enough for most instances and ‘everyday’ use. On those occasions when you’ve been limited by time and circumstance (very low light for example) or when you make a mistake and accidentally choose the wrong settings, it’s good to know that there’s a bespoke tool to help fix that, and that’s where PureRaw fits perfectly.

There’s no doubt that the results on a ‘bad’ image are very impressive. What I would have loved to have had, though, is more control over the filters. In ACR, for example, I can specifically target colour noise reduction, I can choose the balance of noise reduction and loss of sharpness, and so on. In theory the algorithms of PR are supposed to be making those best choices and balances for you, but it feels a bit hollow without the ability to adjust it yourself.

A little like Super Resolution in Adobe Camera Raw, PureRaw is a tool to use when certain limitations have been reached, like you want to rescue images from an old camera that aren’t great quality, or you need to clean up an image for a larger print. DxO apps are a competitive, high-quality pay-outright alternative to subscriptions. Whether that’s worth the price point—£115—or not is a decision you’ll have to make, but in the meantime it’s worth giving the 30-day free trial a try if you’re curious.

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