Life Module Use (v1.5-v1.7-)

Notes from users, documentation addendums.
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Life Module Use (v1.5-v1.7-)

Post by Guy »

Here are some notes relating to using this module. It is not the only way to use the module - please experiment and provide feedback.
They relate to StarTools versions 1.5 to 1.7.427.
Please let me know if anyone sees any errors or has any additional advice they think helpful so this post can be improved.
I will update this post as needed.
For an index of similar notes on the other StarTools modules see StarTools Main Window Use.

Life Module

  • To bring back life into an image by remodelling uniform light diffraction. Removes the flatness that heavy processing can cause bringing back some of the 3d effects.
  • To lift objects from very noisy data or dense star fields.
For a general overview see Life: Global Light Diffraction Remodelling of Large Scale Structures.

Useful Sources
The video 'StarTools: Lifting structures from heavy noise with the Life module' shows the use of Isolate preset with mask set: From the start to 5m27s.

When to use:
  • Towards the end of the workflow - usually just before using the Color module or the final Denoise.
Example Workflow (v1.5):
AutoDev-{Band/Lens}-Bin-Crop-Wipe-AutoDev(or Develop)-{Decon/Sharp/Contrast/HDR/Flux/Life}-Color-{Filter}-Denoise-{Layer/Magic/Heal/Repair/Synth}
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

This is a way of using the module which should give good results in most cases:
Isolate preset - to push back noise/starfield.
  1. Select Isolate preset - this sets most of the controls to their optimum.
  2. Set Strength - to adjust the impact of the Life module. Normally somewhere between 30-100% - use your judgement.
  3. Set Saturation - Change this to adjust the amount of 'glow'.
Other Presets - to add 'life' to the image - increased glow and a more 3-dimensional effect.
  1. Select Heavy, Medium or Less=More preset depending on the type and amount of effect needed.
  2. Set strength - to adjust the impact of the Life module. Normally somewhere between 50-100% but can be less - use your judgement.
  3. Set Saturation - Change this to adjust the amount of 'glow'.
  4. When you are finished 'Keep' the result.
What result to look for:
  • Isolate Preset - objects should be lifted from the noise and background stars. Watch for halos around bright stars.
  • Shroud preset - The image should look brighter without background noise or starfields being more prominent.
  • Other presets - Images should look less flat and detail looks more 3-dimensional.
After Use:
  • Often followed by the Color module.
Special Techniques:

Push Back noise using the Isolate preset with a mask.
This is described in the video 'StarTools: Lifting structures from heavy noise with the Life module' from the start to 5m27s.
  1. Open the Life module.
  2. Create a mask which is initially clear but which you put green in the areas of detail you want to exclude.
    • for long thin wisps (e.g. veil) - create a trail of individual green pixels (Using Single Pixel Toggle Brush Mode) then use Grow until they join up and cover the whole area of detail.
  3. Press 'Isolate' preset.
  4. Increase 'Mask Fuzz' to 3-4.
  5. Press 'Do'.
  6. Press 'Keep' when happy with the result.
Description of Controls:

For general instructions on using mask see Mask.
  • A mask can be used to selectively 'add life'.
  • The mask can be used in conjunction with the 'Isolate' preset to select the object(s) to be lifted.
  • Moderate - Applies a moderate application of the 'life' algorithm.
  • Heavy - A more aggressive application of the 'life' algorithm.
  • Less=More - Applies a light application of the 'life' algorithm.
  • Shroud - Helps brighten an image without emphasising background noise or starfields.
  • Isolate - Lifts objects from noisy data.
Inherit Brightness, Color
Sets whether brightness or colour information is preserved.
  • Brightness
  • Color
  • Off
  • Default is Off (Moderate preset).
Glow Threshold
Sets how bright a pixel needs to be in order to be considered for diffraction.
  • Range is 0% to 100%.
  • Default is 12% (Moderate preset), 5% (Heavy), 4% (Less=More), 3% (Shroud), 0% (Isolate).
  • Setting a lower value will cause more pixels to be processed and so processing will take longer.
Output Glow Only
Set if only the calculated diffracted light (glow) is output.
  • Default is No.
Sets the colour saturation level of the extracted diffracted light (glow) before it is combined with the original.
  • Range is 0% to 500%.
  • Default is 50% (Moderate, Heavy, Less=More), 75% (Shroud), 100% (Isolate).
  • Change this to adjust the amount of 'glow'.
Detail Preservation
Sets the way that Life preserves the detail in the parts of the image to be brightened.
  • Off - does not preserve any detail.
  • Min Distance to 1/2 Unity - uses the pixel that is closest to half unity.
  • Max Contrast - uses whatever pixel maximises contrast.
  • Linear Brightness Mask - uses a brightness mask that progressively masks out brighter values and uses the original values instead.
  • Linear Brightness Mask Darken - uses a brightness mask that progressively masks out brighter values. Only pixels that are darker than the original image are kept.
  • Default is 'Min Distance to 1/2 Unity' (Moderate & Heavy preset), Linear Brightness Mask (Less=More, Shroud & Isolate).
Detail Preservation Radius
Sets a filter radius that is used for smoothly blending processed and non-processed pixels, according to the algorithm specified.
  • Default is 20.0 pixels. Range is 1.0 pixel to 50.0 pixels.
Compositing Algorithm
This setting defines how the calculated diffraction glow is combined with the original image:
  • Screen - works like projecting two images on the same screen.
  • Power of Inverse - Combination based on Power of Inversed Pixels (PIP) function.
  • Multiply, Gamma Correct - multiplies foreground and background and then takes the square root.
  • Multiply, 2x Gamma Correct - as above but doubles the Gamma Correction.
  • Default is 'Power of Inverse' (moderate), Screen (Heavy preset), Multiply, Gamma Correct (Less=More, Isolate), Multiply, 2x Gamma Correct (Shroud).
Controls the overall strength of the effect.
  • Range is 0% to 500%.
  • Default is 100% (for Moderate, Heavy, Isolate presets), 50% (Less=More), 75% (Shroud).
Airy Disk Sampling
Sets the number of samples in the Airy disk point spread function (PSF).
  • Default is 128 x 128 pixels. Range is 128 x 128, 256 x 256, 512 x 512 pixels.
  • Increasing this value will give a more accurate simulation but will take longer.
Airy Disk Radius
Sets the radius of the Airy disk point spread function (PSF) that is used to diffract the light.
  • Default is 8 pixels. Range is 0 pixels to 64 pixels.
  • There are subtle rings around the stars after processing. The way this looks can be adjusted using this setting.
Mask Fuzz
When using a mask, this sets the smoothness of the transition between masked and non-masked elements.
  • Default is 1.0 pixel. Range is 1.0 to 40.0 pixels.
  • Increase to make the transition smoother - values of 10 pixels are common.
Background Notes:

Adding Life - Modelling Light Diffraction
The Life module tries to compensate for the fact that some sorts of processing can cause bright objects to lose their 'glow'.
It assumes the light went through a perfect lens with a circular aperture and produced an Airy Disk.
It tries to model the original Airy Disk by taking the energy represented by the sample pixels and redistributing that energy into an Airy disk.
This is done using a point spread function that produces an Airy Disk diffraction model. The calculated Airy Disk diffraction model is then added back into the original image.

Airy Disk
The Airy Disk diffraction model is defined by the following settings:
  • Glow Threshold - Defines how bright a pixel needs to be before it is included in the Airy Disk diffraction model. This defines the area that is to be redistributed.
  • Airy Disk Radius - Sets the radius of the point spread function - dictates how the resultant Airy Disk diffraction model looks.
  • Airy Disk Sampling - defines the accuracy with which the point spread function defines the Airy disk diffraction model. Greater accuracy takes longer.
Adding the Airy Disk model back into the image.
The calculated Airy Disk diffraction model is added back into the image in two steps.
  • Creating a composite of the model and the original image
  • Selectively merging the composite with the original image.
The process is controlled by the following settings:
  • Compositing Algorithm - this defines how the contribution from a pixel in the Airy Disk model is combined with the contribution of the corresponding pixel in the original image (e.g. Screen, Power of Inverse, Multiply, Gamma Correct) to create a composite.
  • Detail Preservation - Defines how to decide between the detail in the image and the diffraction model composite, or the proportions of both. This is done by selecting the algorithm to use in merging the composite of the model and the original image back into the image.
    • Off - None of the detail is preserved - the area to be redistributed is completely replaced by the new Airy Disk.
    • Linear Brightness Mask - uses a brightness mask with a linear relationship between input and masking - and with the composite of Airy Disk model and original as input - so, as the composite gets dimmer it masks out more of the composite and uses more of the original instead.
    • Max Contrast - chooses between the composite and image detail values based on which adds most contrast with its neighbouring pixels. Takes the Detail Preservation Radius as a parameter.
    • Min Distance to 1/2 Unity - chooses between the composite and the image detail values based on which value is closest to 1/2 unity (gray). Pixels closest to gray tend to show the most human detectable detail. Takes the Detail Preservation Radius as a parameter.
  • Detail Preservation Radius - used with binary either/or Detail Preservation algorithms to smooth the transition. As you move away from where a processed (composite) pixel is selected, a greater proportion of the relevant non-processed (original image) pixel is combined until there is no processed pixel contribution. This parameter defines the radius of that transition. Used in the Detail Preservation algorithms 'Min Distance to 1/2 Unity' and 'Max Contrast'.
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