Author Topic: Stretching; Masked Stretch or Histogram Transformation ?  (Read 2671 times)

Offline russp

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What's the current thinking on the preferred process for stretching an image - I was under the impression that Masked Stretch was introduced to be a improvement on Histogram stretch but most tutorials I see are still using Histogram stretch. I've tried both on a number of images and can see contrast is reduced using masked stretch but also see references to this being recovered later.

Thanks for any Guidance

Offline chris.bailey

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Re: Stretching; Masked Stretch or Histogram Transformation ?
« Reply #1 on: 2017 January 26 06:18:56 »
I think a lot depends on the images you are processing. The beauty of MS is that it helps to reduce the star bloat introduced by HT BUT it can tend to create unnatural looking star profiles with very bright cores.

I tend to use both, I'll do Masked Stretch to a target background of 0.07 over 500 iterations with very low clipping (1/10th of the default) and then use HT for the final bit of the stretch. For me that gives a lot of the benefits of MS without the issues.

Chris

Offline wimvb

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Re: Stretching; Masked Stretch or Histogram Transformation ?
« Reply #2 on: 2017 January 28 12:09:44 »
Whenever I use masked stretch, I first repair the cores of bright stars. I use the process as described by Alejandro Tombolini ( http://pixinsight.com.ar/en/info/processing-examples/28/maskedstretch-stars-sores.html ). Depending on the image, I may use 0 for the clipping value. After MS, I follow up with histogram transformation.
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Offline jkmorse

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Re: Stretching; Masked Stretch or Histogram Transformation ?
« Reply #3 on: 2017 January 28 17:39:04 »
Unless your stars are a problem, HT is still the best, but Harry's Astroshed site has a great tutorial about doing both and then combining them to get the best effect. 
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