HDR Module Use

Notes from users, documentation addendums.

HDR Module Use

Postby Guy » Tue Feb 07, 2017 9:03 am

Here are some notes relating to using this module. It is not the only way to use the module - please experiment and provide feedback.
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.
To see a full alphabetical list of module topics click here.

HDR Module

Purpose:
  • To optimise an images medium-to-small local contrast.
Description:
For a general overview see HDR: Automated Local Dynamic Range Optimization
The HDR module digs out small detail hidden in the image. It provides an automated curve manipulation. HDR can operate on the either the image detail brightness, colour, or both.

Useful Sources
The Unofficial guide is also a good source of help. It relates to version 1.3.5 so there may have been small changes. The notes below relate to StarTools version 1.4.
The processing tutorial video M8 in Color with modest data describes the use of the HDR module between 5m58s and 6m22s.
The Hangout discussion of StarTools with Ivo discusses the HDR module between about 1h02m and 1h07m.

When to use:
  • After the final global stretch (Develop or AutoDev) and the Decon module (if used).
  • Can be re-used if you have a number of different HDR problems - at different scales for instance.
Example Workflow:
AutoDev-{Band/Lens}-Bin-Crop-Wipe-AutoDev(or Develop)-{Decon/Sharp/Contrast/HDR/Flux/Life}-Color-{Filter}-Denoise-{Layer/Magic/Heal/Repair/Synth}
Key: {...} optional modules


Method:
This is a way of using the module which should give good results in most cases:
  1. Select the appropriate preset: Optimise, Equalize, Tame, Reveal - see options below.
  2. Adjust the Detail Size Range to target the size of detail you want.
What result to look for:
  • Enhanced detail in the area you targeted.
After Use:
  • Re-use the module to target other areas as needed.
  • Use the other optional modules as shown in the workflow. Then use the Color module.
Description of Controls:

Presets:
Sets values for the Algorithm, Dark/Bright Response, and Detail Size Range settings.
  • Optimise - accentuates detail it can find (uses Optimize Soft algorithm).
  • Equalise - brings out detail in both shadows and highlights.
  • Tame - brings out detail in bright areas such as galaxy cores, like Equalize but doesn't brighten faint detail.
  • Reveal - reveals details in almost-overexposed cores (uses the Reveal DSO Core algorithm).
Algorithm
Select the main algorithm HDR will use - linked to the presets:
  • Equalize - brings out detail in both shadows and highlights.
  • Optimize Soft - accentuates detail it can find.
  • Optimise Hard - a more aggressive version of 'Optimize Soft'.
  • Tame Highlights - brings out detail in bright areas such as galaxy cores, like Equalize but doesn't brighten faint detail.
  • Reveal DSO Core - reveals details in almost-overexposed cores.
  • Reveal All.
  • Brighten Dark - brings out detail in dark areas such as galaxy cores, like Equalize but doesn't tone down highlights.
  • Defaults to 'Reveal All'.
Dark/Bright Response
Sets how strong the effect of the algorithm is in the brightest and darkest parts of the image.
  • Default is 1.00. Range is from 0.00 to Full (10.00).
Strength
Sets how strong the effect should be overall - applies to the Reveal algorithm only.
  • Default is 1.0. Range is from 1.0 to 3.9.
Small Detail Precision
Sets the degree of precision HDR should use to identify small detail - affects speed of processing.
  • Values of Max, Medium (Faster), Low (Fastest).
  • Default is 'Max'.
Detail Size Range
Sets what detail size HDR should concentrate on in order to bring out the most detail.
  • Default is 20 pixels. Range is from 0 pixels to Max width.
  • A small setting will separate out the details and make them stand on their own. This highlights detail but may seem harsh or flat.
  • A large setting will make the details fit in with the rest of the image. This will appear soft and natural but some detail may seem obscured.
Channels
Sets whether HDR should work on brightness detail, colour detail or both.
  • Values of 'Brightness Only', 'Color Only' or 'Brightness and Color'.
  • Default is 'Brightness Only'.
Background Notes:
The HDR module uses algorithms considered better than techniques like wavelet layers, or global manipulation of shadow, midtone and highlight.
The HDR module takes into account psycho-visual theory (i.e. the way human vision perceives and processes detail). The result is an artefact free, totally natural looking image with real detail that does not suffer from the problems that other approaches suffer from, such as looking 'flat', looking too busy, or blowing out highlights such as stars.
Guy
 
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Joined: Thu Feb 19, 2015 8:35 am

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