Author Topic: Distorted image from HDR Combination  (Read 2602 times)

Offline Mick G

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Distorted image from HDR Combination
« on: 2014 October 27 17:58:51 »
I am trying to process an image of M42 with 6 different length exposures. This is the process I followed:

Run each time frame of images separately in Batch Preprocessing to get one image for each group.

Open Star Alignment
For the Reference Image pick one of the images from the middle of the range of times available
Put the rest of the images in Target images
Leave default settings for Star Detecting and Star Matching
pixel interpolation – Lanczos-3
Output to a separate file for next step
Apply Global

Open HRD Composition
Put all the files from Star Alignment output file, plus the reference image into the input images of HRD composition
Apply Global

When I get the combined image and apply the STF I get A distorted image.  It really looks bad.  See attachment one


I can fix the image with this process:
I open Histogram Transfer Tool,  Open the image, select the image in the HTT,, Open STF, Click auto Stretch, Carry New instance to the bottom of the HTT from the STF, reset auto stretch on STF, Click Apply on the HTT.  What I get is a beautiful image but it is no longer linear.

I'm not sure how to get an undistorted  linear version of my image for processing.
« Last Edit: 2014 October 27 18:14:14 by Mick G »

Offline Alejandro Tombolini

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Re: Distorted image from HDR Combination
« Reply #1 on: 2014 October 27 20:11:19 »
When I get the combined image and apply the STF I get A distorted image.  It really looks bad.
Hi Mick, the result of your HDR is posterized. Apply 24 bit STF button in the STF tool bar.

Saludos, Alejandro.

Offline Mick G

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Re: Distorted image from HDR Combination
« Reply #2 on: 2014 October 28 03:43:02 »
Is there something that I have done to cause the image to be posterized?  How do I prevent it in the future?  Most importantly, do I need to make some correction before I continue processing?

Offline pfile

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Re: Distorted image from HDR Combination
« Reply #3 on: 2014 October 28 09:14:37 »
it is because the HDR result has 64-bit pixels and can not be mapped cleanly to the screen without the 24-bit STF. it's totally normal. once you stretch the image the posterization will go away.

rob

Offline cdesselles

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Re: Distorted image from HDR Combination
« Reply #4 on: 2015 February 18 12:31:36 »
it is because the HDR result has 64-bit pixels and can not be mapped cleanly to the screen without the 24-bit STF. it's totally normal. once you stretch the image the posterization will go away.

rob
Very interesting...  Answers some of my own questions.  Thanks!  :)
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Offline MikeOates

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Re: Distorted image from HDR Combination
« Reply #5 on: 2015 February 19 01:51:35 »
Mick,

There is one operation you have missed out and it may be causing problems... You should crop each integration after the Star Alignment process to remove the black borders. The black 'may' cause HDR to not work properly.

I don't know if your familiar with the DynamicCrop tool, but you should make a crop selection to ensure the same crop will remove the borders from each of the integrations. But before you actually do the crop, drag the triangle at the bottom left of the crop tool to the desktop and close the crop tool without applying it. Now all you do to ensure each integration gets an identical crop is to drag the crop icon on to each of the images and each will have the same crop.

After cropping you then perform the HDR process.

Mike