PhotoLab offers five noise reduction algorithms.
The function is called “DxO Denoising Technologies” (sic).

* High Quality, conventional noise processing to be manually adjusted when post-processing raster images (usually JPEG)
* HQ (fast) is a very powerful processing to be applied by default on raw photos.
PhotoLab’s preview window (the main window that shows corrections) includes HQ processing all the time
* PRIME (Probabilistic Raw IMage Enhancement) is known to preserve details and colors. It restores depth to unblocked shadow areas. Its application is stunning on photos taken with older cameras.
* DeepPRIME is more subtle than PRIME. This improved algorithm better preserves color rendering, whether dull or saturated, and enhances micro details
* DeepPRIME’s new denoising functionality: DeepPRIME XD, version “eXtreme Details” offers improved detail and denoising capabilities. 

PRIME  and its variants are available with PhotoLab Elite Edition.

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It is recommended to leave HQ (fast) noise reduction active at all times. The software divides the image into areas according to their density. It will process them as closely as possible depending on the characteristics of the camera, ISO sensitivity and luminance, or even apply no noise reduction at all.

In both versions DeepPRIME calls its own demosaicing algorithm which turns out to produce more detailed images.
It may be a good idea to systematically process with DeepPRIME all high ISO photos as well as those for which shadows have been planned.
– For scenes with high light dynamics, DeepPRIME cleans up shadows while preserving colors
– (very) dark scenes are by nature unfavorable to colors. DeepPRIME preserves them but does not work miracles if the colors are too narrow

On the other hand DeepPRIME can highlight skin defects (points, freckles, etc.). Use a negative microContrast Local Adjustment mask.

DeepPRIME XD sometimes needs to be refined to get the most out of it.
– The Noise model (Detail) slider applies additional softening or sharpening to the image. ATTENTION of artefacts. The value “0” should therefore be preferred by default
– The Luminance slider allows to define the level of grain smoothing
– The auto value of the dead pixels slider increases for very long exposure times (> 1s). Otherwise it is unique for all cameras, at all ISO speed
– The magic wand resets the recommended values

DeepPRIME requires a muscular configuration with a compatible graphics card (GPU). Transferring the DeepPRIME demosaicing load to the GPU frees up the processor (CPU) to continue working on a stable machine.
The export times risk being very long without a compatible GPU.

When PhotoLab is first launched, this choice is made by DxO.
The Edit / Preferences – Performances – Selection between CPU or Graphics Card menu is used to neutralize or force the activation (it’s worth trying) of incompatible graphics cards. Otherwise leave it on Auto.

<< more infos on DxO support >>

Here is a tip for users with a low power machine.
– Export overnight with the option “Export in DNG with optical corrections and DeepPrime”
– Then develop these DNG photos by benefiting from the noise processing carried out (permanent display)

PRIME processings consume a lot of resources, it is not possible to display its effect permanently.
Its action is previewed in a thumbnail whose selection frame can be moved.

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When exporting the image, noise reduction is performed at the very beginning of the development process, even before demosaicing. This is done under better conditions and the result is immediately more precise.
Unlike competing software whose noise reduction algorithms degrade the image, Optical Sharpness and MicroContrast corrections are performed on a better basis.

On particularly dirty images the output file size decreases as the noise reduction performance increases. 
What could be interpreted as a loss of detail, is in fact the illustration of an artifact-free image.
As an indication, This is the size of the different files of the same JPEG image.

6.4 Mo2.7 Mo2.2 Mo1.6 Mo1.3 Mo

It is possible to filter the thumbnails of images according to the quality of the noise reduction used.

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About the first release of the PRIME algorithm:

The recommended power (by the magic wand) of the Luminance blurs too much detail. My own preset setting, “0- Standard”, is set to 30 which still effectively attenuates the fine grain.  

Note that the luminance value 0 still removes noise.

PRIME’s Maze setting change the Labyrinth pattern visibility by counteracting the phenomenon which may appear on a frame with a frequency different from that of the DC sensor pixels.Previous versions of DxO Optics Pro processed it automatically, but at the price of general reduced acutance details to fight against a marginal phenomenon.
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