Compose Module Use

Notes from users, documentation addendums.

Compose Module Use

Postby Guy » Tue Sep 03, 2019 7:16 pm

Compose Module

Here are some notes relating to using this module. It is not the only way to use it 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.

Purpose:
  • To allow the loading of separate files representing Luminance and Red, Green and Blue colour channels to enable complex composites.
Description:
The Compose module is used to load and combine multiple files into a single image. Either standard luminance, Red, Green and Blue data or a combination of narrow-band data using different filters.
This allows simple creations of complex composites such as LLRGB
It can also be used to extract the Red, Green or Blue channel from a colour image.
If a channel is missing it can interpolate from the other channels to create the missing channel.
The balancing (weighting) of the different channels is done automatically based on the total exposure time for each channel.
While Tracking is on the 'Compose' button is lit up to show processing is being done in a special 'Compose' mode.
In the Compose Mode luminance and colour datasets are processed separately in parallel in subsequent modules.
Bin, Wipe etc until Tracking is turned off.

Useful Sources
There is a useful video here.

The notes below relate to StarTools version 1.5.

When to use:
  • At the start of processing if you need to load files representing different channels - either traditional LRGB or other combinations such as Hubble Pallette (SII, Ha, OIII)
Method:
  1. Preparation:
    • All the image files must be aligned (registered). When stacking, use one image as a reference for the others.
    • If a luminance file has been loaded, any Red, Green or Blue file subsequently loaded must be either exactly the same size or exactly half the size of the luminance file. This allows luminance channels to be 1x1 binned while R,G and B files can be 2x2 binned. In all other cases all loaded files must be the same dimensions.
  2. The Compose module can be set to interpolate any missing channels. Just set Channel Interpolation on and load what channels you have.
  3. If you have any Luminance data, load that first. If you don't you must specify a Synthetic Luminance option in 'Luminance, Colour' setting otherwise the 'Compose' mode will not be enabled.
  4. Load any Red, Green and Blue data you have.
  5. If there is a difference in exposure time between Red, Green and Blue data set the Ratio settings accordingly.
  6. If you have problems loading data because of the error: 'The dimension of the bitmap you're trying to load differ from the previously loaded file bitmap(s). ...' then check the dimensions of individual data files by loading them in StarTools individually. The dimensions are listed to the right of the file name at the top of the screen.
What result to look for:
  • Make sure all the channels are properly aligned. In rare cases it is possible for the registration to be out.
After Use:
Continue with your preferred workflow.

Special Techniques:

Loading Narrow Band data using the Hubble Palette
  1. Load the Luminance data - if you have it - into the Luminance channel.
  2. Load the SII data into the Red channel.
  3. Load the Ha data into the Green channel.
  4. Load the OIII data into the Blue channel.
  5. If you want to create a weighted synthetic luminance channel set the 'Luminance, Color' to 'L + Synthetic L from RGB, RGB'
  6. Otherwise if you have Luminance data (and don't want to use LLRGB) set the 'Luminance, Color' to 'RGB, RGB'
  7. Set the Total exposure times for each channel.
  8. Press 'Keep' when done.
See also the description: LRGB & Hubble palette

Creating a Synthetic Luminance channel from Wide Band data
  1. Load the Wide band image data into the Red, Green and Blue channels.
  2. Set the 'Luminance, Color' to 'L + Synthetic L from RGB, RGB'
  3. Set the Total exposure time for each of the Red, Green and Blue channels.
  4. Press 'Keep' when done.
There is a useful video Painlessly re-creating the iconic Hubble "Pillars of Creation" in StarTools.

Creating a Synthetic Luminance channel from OSC/DSLR Wide Band data
In this case the data has been debayered - and you need to adjust the total exposure time to compensate for the effect of the Bayer matrix. As of StarTools v1.5.366 this is done by default to standard OSC/DSLR data that is not white-balanced - there is no need to use the Compose module to get the advantages of Compose mode.
  1. Load the Wide band image data into the Red, Green and Blue channels.
  2. Set the 'Luminance, Color' to 'L + Synthetic L from RGB, RGB'
  3. Set the Total exposure time for each of the Red, Green and Blue channels - set the Green channel to double the others (assuming RGGB Bayer matrix).
  4. Press 'Keep' when done.
Re-centering blue back onto stars
To recentre a smeared blue channel back to align with the red and green channnels try the following as described in Fringe killer filter add blue back to central star
  1. Optionally Bin the image - then save it.
  2. In the Compose module click Blue and navigate to the file just saved. This will load only the Blue channel of the saved image. The other channels will be automatically set due to 'Channel Interpolation'. You end up with a black & white representation of the blue channel
  3. Process this image so that you reduce the bloating of the stars in the blue channel
    • Do AutoDev or Develop - this allows us to see what we are doing.
    • You could then use the Decon module - set to 'De-ring Mask Gaps, Show Result', set Iterations to 1, set Radius to 3.2 (as appropriate).
  4. 'Keep' the result.
  5. Use Restore selecting 'Linear, Wiped, Deconvolved' option - this reverts to an image which is Linear but which retains the deconvolution you did.
  6. Save the image.
  7. Use the Compose module to load the Red and Green channels (also 50% binned) and load the saved image into the Blue channel.
  8. You should now have an image with a better focused blue channel. Process as normal.
  9. When using the Color module, the Scientific mode may have problems with the star cores as they have artefacts in the blue channel due to the deconvolution. Either:
    • Reduce Bright Saturation right down and set Saturation Amount to 100% or lower. This will avoid recovering colour in the highlights, or
    • Use a star mask to mask out the stars - they then won't be involved in setting the colour balance, or
    • Use Artistic mode

Description of Controls:

Luminance button
Allows you to navigate to and load the Luminance file.

Red Button
Allows you to navigate to and load the Red channel file.
  • If a luminance file has been loaded then any Red, Green or Blue file subsequently loaded can be either the same size or exactly a quarter of the resolution of the luminance file. This allows luminance channels to be 1x1 binned while R,G and B files can be 2x2 binned. In all other cases all loaded files must be the same dimensions.
  • If loading a colour (RGB) image - extracts the Red channel.
Green Button
Allows you to navigate to and load the Green channel file
  • If loading a colour (RGB) image - extracts the Green channel.
Blue Button
Allows you to navigate to and load the Blue channel file
  • If loading a colour (RGB) image - extracts the Blue channel.
Luminance, Color
Defines how to combine the data from each channel.
  • RGB, RGB - Uses the luminance from the R,G and B channels, and the colour from the R,G and B channels.
  • RGB, Mono - - Uses the luminance from the R,G and B channels, does not output colour.
  • L, RGB - Uses the luminance from the L channel, and the colour from the R,G and B channels.
  • L + Synthetic L from RGB, RGB - Creates synthetic luminance data from the R,G and B channels and adds it to the luminance channel, and the colour from the R,G and B channels. Also known as LLRGB.
  • L + Synthetic L from RGB, Mono - Creates synthetic luminance data from the R,G and B channels and adds it to the luminance channel, does not output colour.
Channel Interpolation
The Compose module can be set to interpolate any missing channels.
  • Just set Channel Interpolation On and load what channels you have. This feature can be used to:
    • Generate a missing green channel in the case of an Ha/Hb composite
    • Generate a greyscale from a single Ha, Hb, OIII or SII frame which may later be turned into a false colour image using the Color module.
  • Default is On
Luminance File
Shows the path of any file loaded in the Luminance channel.
  • Default is None.
Red File
Shows the path of any file loaded in the Red channel.
  • Default is None.
Green File
Shows the path of any file loaded in the Green channel.
  • Default is None.
Blue File
Shows the path of any file loaded in the Blue channel.
  • Default is None.
Lum Total Exposure
Sets the total exposure time of the luminance data.
  • Default is Not Set. Range is 1 minute to 720 minutes.
Red Total Exposure
Sets the total exposure time of the red data.
  • Default is Not Set. Range is 1 minute to 720 minutes.
Green Total Exposure
Sets the total exposure time of the green data.
  • Default is Not Set. Range is 1 minute to 720 minutes.
Blue Total Exposure
Sets the total exposure time of the blue data.
  • Default is Not Set. Range is 1 minute to 720 minutes.
Background Notes:

Compose mode
In 'Compose' mode the Wipe module works on the luminance and colour datasets in parallel.
You can see the results of each by pressing the 'Color/Luminance' button in Wipe.
Remember to check both results.

As of StarTools v1.5.366 standard OSC/DSLR data that is not white balanced uses the Compose mode by default.
Guy
 
Posts: 96
Joined: Thu Feb 19, 2015 8:35 am

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