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Re: [APML] A little M31 & M45
Hi Chris,
> [...] how much smoothing is the limit or
> considered acceptable in film shots?
IMO the limit of noise reduction is always imposed by the necessary
preservation of significant structures. When significant details start to
fade out, then one is definitely going too far. Obviously, the main problem
is being able to distinguish what is significant and what's not, and being
able to make such decisions in a consistent way. This can be a matter of
personal preferences, as usually happens in astrophotography. However I
think there are reasonable limits, which one must discover with practice and
by a critical perspective of one's own work. It is also very important to
use the correct processing techniques, in order to avoid artifacts and
uncontrolled destruction of image data.
I agree there is a certain level of "comfort noise" that most people hope to
find in astrophotos. There is a strong trend to identify smoothness (or
absence of noise at high spatial frequencies) with lack of resolution, when
actually this is not necessarily the case.
Regarding Scott's M45, I don't think it's too smooth, but to make sure I
would need to see larger versions of the image before and after noise
reduction.
Look at this example. This is a crop of a raw film image:
http://pleiades-astrophoto.com/tmp/nr-tests/nr_test_1.jpg
And this is the same crop processed with development versions of SGBNR and
multiscale noise reduction (wavelets) algorithms:
http://pleiades-astrophoto.com/tmp/nr-tests/nr_test_2.jpg
I am very interested in knowing the opinions of the people here. Is the
image above too smoothed?
Regards,
Juan
________________________________________________________________________
Juan Conejero, Pleiades Astrophoto Team
PixInsight Home Page: http://pleiades-astrophoto.com/pixinsight/
________________________________________________________________________
----- Original Message -----
From: "Chris Schur" <comets133@yahoo.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Tuesday, December 07, 2004 10:56 PM
Subject: Re: [APML] A little M31 & M45
> Scott, I like both images alot. I am intruiged by C.
> Cooks comment on the smoothing. How much is too much?
> I agree if the image looks like its made of plastic,
> thats too far. In your case it does not, but lacks
> any grain at all. Thats the way the true sky is! Of
> course there is no "grain" in the real nebula. But
> years of fast grainy films have hardened many of us to
> expect SOME grain in every image, even if its not
> really there in space. As I have found by similar
> comments on my images, I can satisfy most people if I
> leave a small but visible amount of noise in the
> picture after the grain smoothing process. Can anyone
> add to this, how much smoothing is the limit or
> considered acceptable in film shots?
>
> Chris Schur (the other chris...)
> --- Scott Hammonds <shammonds@creatorsview.com> wrote:
>
>> Here are two more shots from my trip to New Mexico
>> in October, I'm almost
>> through posting these, I promise.
>> Both were taken with my 4" Tele Vue refractor using
>> hypered RG200 select.
>> Although not spectacular compared to some of the
>> past posts here, they are
>> probably my personal best on these targets. I used a
>> mask blur technique
>> from Jerry's book to help reduce the grain, which
>> wasn't terrible with this
>> film.
>>
>>
> http://www.creatorsview.com/astrophoto/nms04/andromeda.html
>>
>>
> http://www.creatorsview.com/astrophoto/nms04/pleiades.html
>>
>>
>> Comments, criticism and observations welcome,
>>
>> Thanks,
>> Scott Hammonds
>> www.creatorsview.com
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