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Author Topic: Shooting and processing DSLR images using DSS and Photoshop  (Read 32101 times)

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Offline NickH

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #30 on: 22:21:10, 14 January, 2008 »
Just seen this...superb write up!

Nice one Daniel

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Offline dciobota

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #31 on: 07:00:46, 15 January, 2008 »
  Thanks guys.  So, does this mean the download works now?

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Offline markcol

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #32 on: 12:41:33, 15 January, 2008 »
Just came across this one Daniel, many thanks for all your work in putting the tutorial together.  :big_clap:


Cheers
Mark
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Offline bte999

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #33 on: 15:18:05, 15 January, 2008 »
Daniel

The download still doesn't work (for me anyway).  The other dowloads work fine so it's not something blocking all downloads.

Terry
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Offline dciobota

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #34 on: 18:12:46, 15 January, 2008 »
  Hmmm, Rob looked into it, couldn't find anything wrong.  Oh well at least the other links work.  With permission, I may put it on my site somewhere as well.

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Offline Starlight

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #35 on: 23:06:58, 15 January, 2008 »
Fantastic advice as per usual
 :big_clap: :big_clap: :big_clap:
It makes me want to go out and buy a DSLR just to try it out  :lol:

Don
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Offline koootzz

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #36 on: 06:31:20, 16 January, 2008 »
I've changed the PDF that is in the downloads section for a zipped version, the download seems to work now.
Leigh
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Offline bte999

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #37 on: 07:22:06, 16 January, 2008 »
Yup, download is OK

Terry
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Offline dciobota

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #38 on: 18:19:46, 16 January, 2008 »
  Awesome Leigh, tried it and it work for me also!  :urock:

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Offline sheri_barri

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #39 on: 02:12:52, 02 February, 2008 »
Very helpful!!  Cheers for writing this up.  Excellent images too.  I may have overlooked something but which scope did you use for the M42 shot?

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Offline dciobota

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #40 on: 17:52:20, 12 March, 2008 »
 Hi Sheri,

 Sorry for the long time to reply, been off forum for a while.  I do believe that the scope I used for that show was a William Optics Megrez 110ED.  Highly recommended scope is your funds allow.

 Daniel
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Offline sheri_barri

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #41 on: 22:51:42, 13 March, 2008 »
Hi Daniel,

I managed to obtain a WO Megrez 110ED last month with a HEQ5pro.  Only had first light on friday and viewed the most stunning Saturn at 205x that I have EVER seen.  Looking forward to some clear skies to get the cameras out!

Cheers for the follow-up.

Sheri
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Offline dciobota

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #42 on: 04:15:33, 14 March, 2008 »
  Ahh, you read my mind then!  :)  Congrats on the new scope, you won't be disappointed.

Daniel
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Offline Simon Hicks

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #43 on: 09:36:18, 17 March, 2008 »
Hi Daniel,
                Massive and very comprehensive write up...really thorough, really cool.

I've just got a question about one part of what you said about darks. You said that darks add noise to the final image...which is absolutely true, as do flats and bias frames. And you said that you used to take as many darks as you did lights. But then you said that because of this you used to use the in camera noise reduction system. And its this I have a problem with.

When you use the in-camera noise reduction system it takes a dark frame immediately after the light frame and does the substraction there and then. So effectively each light frame now has the full noise from one dark frame added to it. You are effectively only using one dark frame for each light.

However, if you take many dark frames (the 20 to 30 that you state in your text) and then create a master dark then this master dark has a much much lower noise level to it. So then if you use that for all of your lights then the noise problem is massively reduced, but you still get the benefits of subtracting the dark signal.

And the same is true of the flats and bias frames. The important thing is to get the valuable dark, flat and bias signals and get the noise level of each down to an acceptably low level.  The dark and bias frames will contain pixel to pixel variations, a signature of the CCD if you like, that is not taken care of by the flats and cannot readily be taken care of by simple post processing.

Of course, taking 20 or 30 ten minute dark frames at the right temperature can be a time consuming practice!

Cheers
           Simon
Simon
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Offline dciobota

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Re: Shooting and processing DSLR images using DSS and Photoshop
« Reply #44 on: 18:52:03, 18 March, 2008 »
  Hi Simon,

  Thanks!  :)

  And you'r absolutely right, what I wrote is definitely counter intuitive and makes little sense.  I would like to blame this on Canon's confusing naming and explanation of their long exposure noise reduction feature.  I've never been able to find an article that explains in depth what Canon's software does with the RAW image when the LNR is turned on beyond the shooting of the extra dark frame and using it in noise reduction.  Here's my educated guess on the process:

 You take the pic.
 Camera takes dark frame.
 Software uses dark frame to identify hot pixels and remove them (I think it uses an average of neighboring pixels, but not certain).
 Software uses the dark frame and light frame to characterize read noise somehow (which is most of the dark frame noise in Canon dslr's) and applies some sort of noise reduction algorithm based on that.  I know, a lot of hand waving is done here, because I just don't know.
 Software determines dark frame background level (probably average value for the entire frame) and subtracts it.
 The processed RAW image is saved.

  I honestly don't think the software does a straight background subtraction, because the noise from a frame that has had LNR applied to it definitely shows less.  Not a huge amount, but noticeable, especially as far as chroma noise is concerned.  Also, I haven't been able to tell if there was any loss of detail at all in the noise reduced image.

 But, say you didn't use noise reduction at all, and just shot light frames.  In that case you would end up with double the light frames for a given session, which would reduce the noise also when stacking. 

  I agree, making a master dark and using it repeatedly would indeed help with keeping the noise to a minimum.  But, the only use I see for a master dark is a) hot pixels  and b) black level values (the pixel/pixel variations you mentioned as far as dark current).  I have had very good success using Kappa Sigma clipping to get rid of hot pixels.  As for the black level values, you're right, it would indeed help there, but I wonder how much really.  On Canon cameras, where the last 1-2 bits are very noisy, I think the pixel to pixel variations fall into that range also.  I must say I never saw any artefacts from enhancing the dark areas of my pics, which would show those variations.

  But I will be the first to admit I'm wrong about this, since I've not looked very carefully at my old master darks.  There could be something there that I'm not accounting for in my technique.  Not the first time I'd be wrong about something.  ;)

Daniel

 
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