Author Topic: M94 - Dynamic range problem  (Read 2940 times)

Offline andrewluck

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M94 - Dynamic range problem
« on: 2015 May 31 10:14:13 »
I'm having some problems with compressing the dynamic range on my image of M94 that I'd appreciate advice on.

The outer halo is extremely faint compared to the inner core. Any suggestions for the workflow I should employ?

https://www.dropbox.com/s/19twindfr2w53tt/M94_HDR_crop.xisf?dl=0


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Offline Zocky

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Re: M94 - Dynamic range problem
« Reply #1 on: 2015 June 04 14:30:47 »
You can use HDRMT. Play around with "number of layers" and you should get pretty decent result.
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Offline andrewluck

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Re: M94 - Dynamic range problem
« Reply #2 on: 2015 June 05 10:11:39 »
I've been trying that. Do I run it multiple times for the different scales within the image? The best I've been able to achieve so far is attached but the colour is rather flat.

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Offline msmythers

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Re: M94 - Dynamic range problem
« Reply #3 on: 2015 June 05 11:45:15 »
Andrew,

This is just a quick look. I didn't do a color balance so I can't say the colors are correct only that there is plenty of color in the image. I used basic steps of MaskedStretch, Curves and ColorSaturation. To bring out the core I used Deconvolution, HDRMultiscale and LocalHistogramEqualization.  Everything was done with a RangeMask and StarMask.


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Offline andrewluck

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Re: M94 - Dynamic range problem
« Reply #4 on: 2015 June 05 13:49:48 »
Thanks Mike, that's reassuring. I'll run through the processing again and see what comes out.

I'll save and upload the process icon and masks next time.

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Offline andrewluck

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Offline pfile

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Re: M94 - Dynamic range problem
« Reply #6 on: 2015 June 05 16:20:39 »
are you sure the subs for this image were debayered properly? there are some horizontal line artifacts in the RGB image that seem a little suspicious to me.

i am assuming this image came from an OSC as shown in your sig

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Re: M94 - Dynamic range problem
« Reply #7 on: 2015 June 05 17:36:55 »
Andrew

I went back and processed your image one more time. Again not doing a color balance as the image seems OK for balance. Stars seem the right color so I don't think there is any debayer issue. Also looking at other images of M94 after finishing this time the galaxy seems close. I did over saturate a bit. Sometimes when I have an image with what seems like very little color in it I will do some color saturation before the stretch. That seems to help later in the processing. That's just me and it might be something you shouldn't do, I don't know.

Anyway here is my second image, the masks and the process icon for the image.


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Offline andrewluck

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Re: M94 - Dynamic range problem
« Reply #8 on: 2015 June 06 08:31:19 »
That's interesting, the blue has come out in the inner ring. This is one very strange galaxy.

I haven't tried anywhere near 10 iterations of HDRMT previously. Looks like I need to be a lot more aggressive with colour saturation.

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Offline msmythers

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Re: M94 - Dynamic range problem
« Reply #9 on: 2015 June 06 09:19:42 »
Andrew,

You can be more aggressive if your masks are not as strong. For me it allows more control. Also the more aggressive color saturation is tempered with the ACDNR color noise reduction. The other noise reduction tools could have been used and might be more effective.

Mike

Offline andrewluck

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Re: M94 - Dynamic range problem
« Reply #10 on: 2015 June 07 05:59:25 »
Mike

I need to rework this again to reduce the damage to the stars but I'm quite pleased with how the galaxy is looking now. Of all the galaxies I've tried this one has been the trickiest and I've learnt a lot.

Cheers
Andrew
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