Flux Module Use

Notes from users, documentation addendums.

Flux Module Use

Postby Guy » Wed Apr 12, 2017 5:46 pm

Here are some notes relating to using this module. It is not the only way to use the module and experimentation is encouraged.
Please let me know if anyone sees any errors or has any additional advice they think helpful.
I will update this post as needed.
To see a full alphabetical list of module topics click here

Flux Module

  • To de-noise, sharpen or augment DSO detail
For a general overview see Flux: Automated Astronomical Feature Recognition and Manipulation.
The Fractal Flux module uses an algorithm which pin-points features in the image by looking for natural recurring fractal patterns that make up a DSO, such as gas flows and filaments. Once the algorithm has determined where these features are, it then is able to modify or augment them.

Useful Sources
The Unofficial guide is also a good source of help. It relates to version 1.3.5 so there may have been some changes. The notes below relate to StarTools version 1.4.
The processing tutorial video StarTools: M42 H-alpha High Dynamic Range composite discusses the use of the Flux module between 10m19s and 10m44s.

When to use:
  • Use after extracting the most detail (i.e. Decon, Sharp Contrast, HDR) and before using the Color module.
  • The noise reduction capabilities of the Flux module can be used in place of the Denoise module where Tracking is not used (for example where an image is not linear to begin with and StarTools is being used just to touch up an image).
  • It could be a decent alternative to the Denoise module after working in the Layer module with Tracking off. In particular, for fine noise due to the way the self-similarity works.
  • Only use once.
Example Workflow:
AutoDev-{Band/Lens}-Bin-Crop-Wipe-AutoDev(or Develop)-{As needed: Decon/Sharp/Contrast/HDR/Flux/Life}-Color-{Filter}-Denoise-{If needed: Layer/Magic/Heal/Repair/Synth}
Key: {...} optional modules

This is a way of using the module which should give good results in most cases:
  1. Select the Wavelet Library size - after a while you will be presented with Screen 2.
  2. Select the desired preset - normally choose Sharpen or Noise - avoid using Detail except in special circumstances.
  3. Keep the result when done.
What result to look for:
  • Any change may be subtle - Use Before/After button to see the change.
  • If Sharpen preset is chosen the image will look sharper in the areas where there is detail.
  • If Noise preset is chosen the noise in the image will be reduced.
Description of Controls:

Screen 1

Wavelet Library
This specifies the amount of 'knowledge' the fractal flux module starts off with. The smaller the amount of knowledge the more flux you might get.
  • Small.
  • Large.
  • Default is Small.
  • The smaller the amount of knowledge the more flux you might get.
  • A larger wavelet library will make the module better at relating detail to other detail at larger scales (essentially making it more precise), but will also make the effect a lot less "dramatic", especially when noise is involved.
Screen 2

Sharpen preset
This button optimises the settings for sharpening of the image.

Detail preset
This button optimises the settings for adding natural-looking detail to the image.
  • This adds artificial detail but...
  • It can distort stars so using a star mask to mask out stars is advisable.
Noise preset
This button optimises the settings for removing noise from the image.

For general instructions on using masks see Mask.
  • Recommended to use an inverted star mask with this module - Auto, Stars, Do, Invert, Keep.
This selects the filtering algorithm to use. Choose from:
  • Add Detail - Used to add detail to the image.
  • Modulate Unsharp Mask - the presence of flux turns on and off an Unsharp Mask sharpening algorithm. Effectively performs a localized sharpening of only ‘interesting’ features, while leaving others (including noise) alone.
  • Modulate Gaussian
  • Modulate Median
  • Modulate MOMH - Mean of Median Half - 25% upper and lower outlier rejection, taking mean of remaining values - Used to reduce noise.
  • Modulate Undo Buffer- Use when you want to combine an image with another image using the flux to modulate.
  • Default is Modulate Unsharp Mask [Sharpen], Modulate MOMH [Noise], Add Detail [Detail]
  • Use the default setting unless you understand and need the effects the other settings give.
Positive Flux
Controls the amount any positive flux is amplified
  • Default is 500%, 25% [Sharpen], 600% [Noise], Maximum is 1000%
Negative Flux
Controls the amount any negative flux is amplified:
  • Default is 0%, 600% [Noise], Maximum is 1000%
Detail Filter
Sets the minimum allowable size of any flux concentrations.
  • Increasing this value allows only the bigger clumps of flux through.
  • Decreasing this value allows more and more smaller, detailed flux to pass through.
  • Default is 1.0 pixels, 2.5 pixels [Sharpen], Range is 1.0 to 40.0 pixels.
Brightness Mask Power
Sets the power that should be applied to a pixel in the luminance mask if one is set in Brightness Mask Mode.
  • Default is 1.00, 3.00 [Noise], Maximum is 5.00.
Brightness Mask Mode
Sets the mode of the optional masking using the luminance information. Options are:
  • Off
  • Where fg is dark, use bg
  • Where fg is light, use bg
  • Where fg is light & dark, use bg
  • Where fg is grey, use bg
  • Default is 'Off', 'Where fg is light, use bg' [Noise]
Filter Amount
Sets the strength of the Unsharp Mask sharpening.
  • Default is 200%. 100% [Noise], Maximum is 1000%.
Filter Radius
Specifies the maximum size of any details to be sharpened by the Unsharp Mask algorithm (if used) or the filter width for the other algorithms.
  • Default is 1.5 pixels, 12.5 pixels [Noise], Range is 1.0 to 40.0 pixels.
  • The larger the radius the larger the details that are sharpened.
Filter Fuzz
Specifies the kernel radius of an optional Gaussian blur, to be applied to the flux before it is passed to the Unsharp Mask routine for modulation.
  • Default is 1.0 pixels, Range is 1.0 to 40.0 pixels.
  • Increasing this value effectively 'smears out' the flux over a larger area so the detail around the flux is also sharpened.
  • As the flux is spread out its intensity becomes lower. You may compensate for this by increasing the Positive Flux and Negative Flux amplifiers, or by increasing the Filter Amount (sharpening strength) parameter.
Mask Fuzz
If a mask is used, Mask Fuzz controls the blending of the transition between masked and non-masked parts of the image.
  • Default is 1.0 pixels, Range is 1.0 to 40.0 pixels
Background Notes:
The way Fractal Flux works is by analysing the image larger scale structures and gas flows and then tries to apply what it has learned about the larger structures to the smaller structures.
In wide fields, the gaseous structures start behaving/looking materially different than at smaller scales (kind of like how cloud patterns seem to look different from the surface of the earth than they look from high up in outer space where you can see swirls and distinct low/high pressure areas, cloud fronts, etc.), so using very large structures (thousands of light years across) to base smaller structures on when the difference is big, starts becoming harder. Therefore the results will start looking less plausible.
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