Denoise 2 Module Use

Notes from users, documentation addendums.

Denoise 2 Module Use

Postby Guy » Fri Mar 20, 2020 12:12 pm

Here are some notes relating to using the Denoise 2 module.
They relate to StarTools version 1.6.392beta and later
Please let me know if anyone sees any errors or has any additional advice they think helpful.
I will update this as needed.
To see a full alphabetical list of module topics click here.

Denoise 2 Module

Purpose:
To reduce the visual impact of noise while preserving detail.

Description
For a general overview see De-Noise 2: Statistical and Psychovisual Noise Grain Equalisation.
The Denoise 2 module provides an alternative to the standard Denoise module while still exploiting the advantages of Tracking.
The standard Denoise module ends up with a smoothed image with no noise grain visible.
The Denoise 2 module equalises noise grain across the whole image.

Choosing between the classic Denoise Module and the Denoise 2 Module
  • Use this module in preference to the classic Denoise Module where you would prefer a more film-like result where there is a uniform grain in the background.
  • Use the classic Denoise Module where you would prefer a result where noise is smoothed.
Noise reduction is applied at the very end when Tracking is switched off. Due to StarTools' noise evolution Tracking noise reduction will be much more targeted.
This module:
  • Equalises the noise grain across the entire image.
  • Separates Brightness and Colour - this allows separate control of brightness and colour noise.
  • Uses information gained while Tracking was on to help target the noise.
  • Aimed primarily at targeting Poisson (shot) noise.
The Denoise 2 module uses the following methods to reduce the impact of noise:
  • Tracking identifies the areas of higher noise.
  • The noise grain is equalised over the entire image - gives the effect of appearing to have a constant SNR - which avoids the eye being drawn to areas of low SNR.
  • Optionally uses psychovisual techniques - exploiting the fact that we can't easily recognise noise in areas of great detail.

Useful Sources
Ivo's on-line manual page De-Noise 2: Statistical and Psychovisual Noise Grain Equalisation
Some useful information can be found in Links and Tutorials

When to use:
  • Final Denoise is usually done after the Color module - When turning 'Track' off select the option for 'Grain equalisation' noise reduction.
  • The Denoise 2 module can also be used in Preview-Only mode at any time when Tracking is on.
Example Workflow (v1.6):
AutoDev-{Band/Lens}-Bin-Crop-Wipe-AutoDev (or Develop)-{Contrast/HDR/Sharp/Decon/Flux/Life}-Color-{Entropy/Filter}-Denoise (or Denoise 2)-{Layer/Shrink/Heal/Repair/Synth/Stereo 3D}
Key: {...} optional modules

Method:
This is a way of using the module which should give good results in most cases:
  1. Select Grain Size so the noise grain and clumps can no longer be seen - as described below. Structures larger than the Grain Size are considered detail, not noise.
  2. Click 'Next' - StarTools will do its initial attempt using that grain size with other settings at their default values. When complete screen 2 is shown.
  3. Select an area to sample to speed up the processing while you adjust the parameters.
  4. Select the 'Mode' leave in Psychovisual usually - but toggle between the two modes to see the effect.
  5. Adjust the Grain Removal parameter - increase to remove more noise grain.
  6. In many cases the remaining parameters can be left at their default values.
  7. However, if further adjustment is needed then try adjusting Grain Limit Detail and Grain Limit Color - to balance detail loss and noise reduction.
  8. Toggle top 'Support' button (PV only) to see the effect on the gain map.
  9. Toggle top "Pre Tweak/Post Tweak" button to see effect of last adjustment if needed .
  10. Press 'Full' to apply the effect to the full Image.
  11. If you make a mistake, the 'Reset' button discards all the changes since you started using the module.
  12. Press Keep to exit, keeping the results.

What result to look for:
  • Background noise should be greatly reduced or eliminated without affecting detail significantly.
  • Look out for any remaining noise blotches - if found go back and check the Grain Size and Grain Removal settings.
  • Look out for any reductions in the detail - if found try reducing Grain Removal, Grain Limit Detail or Grain Limit Color values as appropriate.
  • Use the 'Before'/'After' and 'PreTweak'/PostTweak' buttons to see the effect of the module and changes.

Ways of getting better results:
  • Improve the Signal-to-Noise ratio (SNR) of the original image - by taking more subs. Also, make sure the subs are long enough.
  • With light polluted data you will need many more subs to get equivalent results.
  • If you have pattern noise try Dithering if you don't already.
  • Make sure you have used the Bin module to reduce the resolution (and improve the SNR) if the image is oversampled.
  • Try using the Life module 'Isolate' preset with no mask set just before using Color and Denoise modules - to help push back the noise.
  • If there is background colour noise this may be de-emphasised by using the Grain Limit Color control.
  • If the background noise cannot be controlled successfully in Denoise 2 or Denoise - it may be necessary to go back and redo Develop/AutoDev to control the final stretch a little to limit the noise to a level Denoise/Denoise 2 can handle. To do this use the Restore - 'Linear, Wiped' button.

After Use:
  • Save the image and finish - or apply one of the modules not available when Tracking is on i.e: Heal, Shrink, Repair or Synth as needed.

Special Techniques:
<Contributions welcome!>

Description of Controls:

Screen 1 - Psycho-Visual Grain Equalization De-Noise

Grain Size:
Allows calibration of the amount of noise by specifying a size where the noise grain, mottling and clumps can no longer be seen.
  • Sets a baseline for maximum noise grain.
  • Default Grain Size is influenced by the setting of the 'Dark Anomaly Filter' in Wipe, Develop and Contrast modules, 'Ignore Fine Detail <' in AutoDev, and 'Grain Size' in Denoise.
  • Default value is 2.0 pixels if none of the above settings are changed from their defaults. Range is from 1.0 to 30.9 pixels.

Screen 2 - Psycho-Visual Grain Equalization De-Noise
Top Buttons
  • Support: Toggles the gain map in Psychovisual mode. Psycho-visual (PV) mode only
Mode:
Selects the algorithms used to control the noise.
  • Statistical - Uniformly equalises noise grain across the image.
  • Psychovisual - In addition to the statistical algorithms, uses also the psycho-visual characteristics - that we find it hard to distinguish noise in areas of detail - and a subjective perception of sharpness based on the edge contrast in an image.
  • Default value is Psychovisual. Range is Statistical or Psychovisual.
Grain Removal
Controls the amount of fine noise grain reduction.
  • Higher values will remove more grain and the image will start to blur.
  • Default value is 50%. Range is from 0% to 100%.
PV Detail Size
Controls the size of the multi-scale support bands used in deciding whether a region is visually 'busy'.
  • Psycho-visual (PV) mode only
  • Smaller values protect the finer details. Increasing the value increases the range of sizes of the details protected.
  • Default value is Grain Size value. Range is from 1.0 to 5.0 pixels.
Grain Limit Detail
Sets the largest visible noise grain size for detail (luminance)
  • Above this size limit larger detail is left completely intact.
  • Reducing this value will reduce the maximum size of detail which is affected.
  • Default value is 2.0 pixels. Range is from 1.0 to 100.9 pixels.
PV Support Gamma
Allows the multi-scale protection of visually 'busy' areas to have a non-linear response.
  • Psycho-visual (PV) mode only
  • 'Busyness' map is non-linesarly stretched.
  • Increasing this value increases the strength of the noise grain preservation in 'busy' areas.
  • Default value is 2.20. Range is from 0.00 to 5.00.
Grain Limit Color
Sets the largest visible noise grain size for color.
  • Above this size limit larger detail is left completely intact.
  • Default value is Grain Size value. Range is from 1.0 to 100.9 pixels.
PV Support Area
Specifies how far noise grain protection of visually 'busy' areas should extend to neighbouring pixels as well.
  • Psycho-visual (PV) mode only
  • Increasing this value extends noise grain preservation to neighbouring pixels - preserving more noise grain - and detail.
  • Default value is 3 pixels. Range is from 'Off'(0) to 20 pixels.

Background Notes:

Evaluating Results
When working on an image over a period of time it is difficult to ensure the changes you make are moving to a 'better' overall image.
It is important to try and see it as if through the eyes of someone seeing the image for the first time.
This is particularly difficult when trying to get the optimum noise reduction.
One useful technique is to look at the image at different levels of zoom to see what effect your changes have at different scales.

Other Notes
See also the background notes in the Denoise Module User Notes
Guy
 
Posts: 105
Joined: Thu Feb 19, 2015 8:35 am

Re: Denoise 2 Module Use

Postby Burly » Fri Mar 20, 2020 6:20 pm

excellent work guy
Burly
 
Posts: 215
Joined: Mon Aug 31, 2015 7:06 am
Location: Northamptonshie uk


Return to User Notes

Who is online

Users browsing this forum: No registered users and 1 guest