Author Topic: Beginner attempting to 'bake' a histogram transformation  (Read 388 times)

Offline mr1337

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Beginner attempting to 'bake' a histogram transformation
« on: 2018 September 09 11:35:46 »
A Pixinsight initiate here....I am having a weird issue where I am trying to 'bake' in an STF that looks ok: https://drive.google.com/file/d/16K5JeTkZMSxq0ceirqSfylkyq7R1QwO_/view?usp=sharing

The problem is I uncheck 'preview' and 'track view' and drag the triangle over to the HistogramTransformation window... It looks much different:
https://drive.google.com/file/d/1lvqNoYNC7p1mpcn7LvXy2AhdpMbQCamf/view?usp=sharing

Once I apply the transformation to the image (by dragging the triangle), it looks different still:
https://drive.google.com/file/d/1KtE1XGoYh2SWejv4WUn2FJ5KaS-BG5uk/view?usp=sharing

Any idea what I could be doing wrong here? The image isn't great to begin with, but was hoping to at least get out what I am looking at on the screen... Many thanks!

Offline John_Gill

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Re: Beginner attempting to 'bake' a histogram transformation
« Reply #1 on: 2018 September 10 03:30:02 »
Hi,

Try this - open your un-stretched image (it should mostly be black with very little detail).  Open the following processes, "Screen Transfer Function" and "Histogram Transformation"  You can leave "Track on" and "Preview" checked.  Click the "reset" button on both processors.  Now on the STF uncheck "Link RGB Channels" then click the "Auto Stretch" button (Radio-active icon)"  if the suggested stretch looks good then click and drag the "execute triangle button" to the bottom bar of the HT process.  This will transfer the STF values to the HT process.  Here you can tweak the settings and now apply the HT to your un-stretched image.

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John

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Offline monkeybird747

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Re: Beginner attempting to 'bake' a histogram transformation
« Reply #2 on: 2018 September 17 13:18:37 »
I’ll add to the above to be sure and reset the screen transfer function once you’ve drug it’s triangle to the histogram transformation window. Otherwise I think your live preview will apply the stretch to the stretched image (double application of stretch), and not represent the changes you are planning on applying to image.

Once you apply the stretch through histogram transformation your preview window will again look off because you are stretching the image you just stretched again. Reset the HT tool after applying the stretch for your preview to be accurate again. This applies to similar tools like curves and saturation. Apply, the reset and evaluate if further application is needed.

Offline Cosmick

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Re: Beginner attempting to 'bake' a histogram transformation
« Reply #3 on: 2018 September 19 03:54:40 »

Any idea what I could be doing wrong here?

The secret is in the histograms. You are severely clipping the image and my guess is that by turning off track image you are now trying to apply the screen stretch from the wrong image.
You can also try resetting the STF settings in case they are messed up somehow and make sure the image you are working on is highlighted.
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Mick

Offline Cosmick

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Re: Beginner attempting to 'bake' a histogram transformation
« Reply #4 on: 2018 September 19 05:02:36 »
The problem is I uncheck 'preview' and 'track view'

Unchecking the preview is OK but I almost never operate with 'track view' unchecked, in fact I wish I could find a way to make checked the default for all processes that support it.
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Mick