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Simple Stacking Question

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#1 MGW

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Posted 22 September 2022 - 09:18 PM

Will "Compositing" multiple RAW frames (shots taken with identical settings, with Long Exposure NR and High ISO NR applied) using Canon DPP software improve the signal to noise ratio similarly to using stacking software? 



#2 sharkmelley

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Posted 23 September 2022 - 01:29 AM

I didn't know what "compositing" was, so I had to look up the documentation:  https://documentatio...P_W_05_10b.html

 

Yes, compositing will improve the SNR, just like stacking because it is a form of stacking.  But can you perform the star alignment during compositing?  It's necessary because, in general, the stars in individual frames are not in exactly the same place due to accidental drift or deliberate dithering


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#3 SpaceMax

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Posted 23 September 2022 - 06:46 AM

All of the above. Also there is no compensation for field rotation involved. DPP offers a tool to blend multiple exposures. That’s helpful to create HDR images of static scenes but used as a means for stacking astronomical images likely produces smeared images with weird colours.
If it’s the lens corrections that attract you to DPP, by all means, one can develop raw files into fully corrected TIFF files (batch process) and stack those TIFFs in DeepSkyStacker. In some instances this works better than stacking raw out of camera.

#4 Iamhondo

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Posted 23 September 2022 - 11:30 AM

Will "Compositing" multiple RAW frames (shots taken with identical settings, with Long Exposure NR and High ISO NR applied) using Canon DPP software improve the signal to noise ratio similarly to using stacking software? 

The obvious (to me at least) question is, "Why wouldn't you just use the common astrophoto stacking software like Deep Sky Stacker or other similar apps?"

The next question is "What's the upside of sticking to DPP?"

You mention the in-camera NR reductions. I don't know what (if anything) DPP does with such images. But generally, for astrophotos, it's recommended that you don't let the camera processor muck to much with your raw image. The NR effects makes each subframe less "raw".

Standard calibration steps for pre-processing raw images is to apply dark frames, bias frames (sometimes), and flat frames to correct image flaws.

Joe



#5 MGW

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Posted 28 September 2022 - 05:06 PM

Shark, Max, Joe,

Thx for your replies.

 

When I began taking pics through a 90mm Mak with a Canon Rebel, there were no stacking options for an iMac, PC only.

Since then I have upgraded my T5i to a 6D Mk II and have had mixed results. The stars seem to get turned all white and I lose color. I think software presets cause this as I can see color b/4 the file gets "drawn." Canon advised that the 6D Mk II excels at high ISO settings. I have found under exposed results are unusable.

 

I typically shoot Landscape Milky Way pics at ISO 12800, exposed for 90-120 sec at f/4-5.6, at 11mm with my 11-24mm f/4L while tracking on a Fornax Lightrack II from Bortle class 2 locations. I process RAW files with Canon DPP b/c that is what I have learned to use.

 

Compositing 5 files does not seem to yield a noticeable difference from a single exposure. The Long Exposure NR results in dark frame subtraction for each file. I DK what High ISO NR does. I am able to align the files manually when using the Compositing tool, otherwise they are a bit off, producing slightly oblong stars. In fact I get various degrees of peripheral distortion noticeable under magnification when viewing single files as well. I can save composited RAW files as JPG or Tiff (8 or 16 bit). 

 

I also shoot at 24mm (24-70mm f/2.8L) and 50mm (50mm f/1.2L). I am completely self-taught having learned by practicing what seems to work best at different settings. I DK the vocabulary yet (bias and flats, etc.). I'll have to get back to the new-learning process. I think I'm at that growing edge.

 

Any comments, suggestions will be appreciated.

 

Michael

 

Please see attached _MG_9861 3_02.JPG:

EOS 6D Mk II, f/5.6, 150 sec, ISO 12800, EF 11-24mm F4L, 11mm, tracking on Fornax Lightrack II. Image captured from Harquahala Mtn Peak, Salome, AZ, 1.5hrs west of PHX off I-10.

Note the Summer Triangle, Vega was at the Zenith. This is a single exposure photograph from a Bortle Class 2 location, appr 4,500 ft above local ground level (5,600 ft above sea level).

Attached Thumbnails

  • _MG_9861 3_02.JPG

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#6 sharkmelley

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Posted 29 September 2022 - 01:49 PM

Compositing 5 files does not seem to yield a noticeable difference from a single exposure. 

That's not good. What settings are you using? You should be seeing at least a factor of 2 reduction in the background noise.



#7 MGW

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Posted 29 September 2022 - 02:19 PM

Thx,

I'll redo and document details.

MGW



#8 MGW

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Posted 29 September 2022 - 04:17 PM

Shark,

 

Redo Workflow Details:

 

• Original RAW file _MG_8348.CR2 (EOS 6D Mk II, f/5.6, ISO 12800, 150 sec, 11mm) 43.7MB. 

• Cropped/Edited RAW 8348.CR2 file. Copied and Applied Edited 8348.CR2 Recipe to each 1 of 4 additional RAW files (8349, 8350, 8351 and 8352.CR2).

• Composited 8348.CR2 (Foreground) and 8349.CR2 (Background) Images. Used Averaging Method.

• Composited the previously composited image (8348.CR2 + 8349.CR2) with 8350.CR2 and composited 8351.CR2 and 8352.CR2, each with the previously composited image. 

• Saved As: "48_49_50_51_52 Comp.JPG." Resized 5.2MB Comp.JPG file to 414KB.

• Converted and Saved single RAW file 8348.CR2 to 8348.JPG. Resized from 5.6MB to 432MB.

• I created 2 files for comparison.

 

Good News. I am able to see a difference between the composited files image and the single file image. This is Great!

Is it realistic to expect that compositing additional files (10-20) will continue to yield improvements over images resulting from compositing fewer files? 

 

I will post each for review in subsequent replies to this topic.

 

Thx,

MGW

 

BTW,

My desktop indicates an image file that is 408KB is only 157KB when posted on the CN Forum.

Attempting to post an image file that is larger, 485KB on my desktop, is disallowed b/c it is too large to post on the CN Forum.

 

Any thoughts about the apparent discrepancy in file sizes?

 

Regards,

MGW



#9 sharkmelley

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Posted 29 September 2022 - 04:22 PM

 

Good News. I am able to see a difference between the composited files image and the single file image. This is Great!

Is it realistic to expect that compositing additional files (10-20) will continue to yield improvements over images resulting from compositing fewer files? 

Yes, the more exposures you average together (i.e. stacking), the better the improvement in noise.  That's the magic of stacking!

 

Mark



#10 MGW

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Posted 29 September 2022 - 04:28 PM

Shark,

 

See Attached Composited Image.

 

MGW

 

48_49_50_51_52 Comp.JPG



#11 MGW

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Posted 29 September 2022 - 04:34 PM

Mark,

 

Single JPG File.

 

MGW

 

_MG_8348.JPG

 

Do I need to Add Attachment to post? Or can I just Add Reply?



#12 sharkmelley

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Posted 29 September 2022 - 04:34 PM

See Attached Composited Image.

It's looking good. However, a lot of the Milky Way has come out BLUE!  I'm not sure what happened there confused1.gif




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