Re: [APML] Process this Raw Image

[<pleiades2004@pleiades-astrophoto.com>]

Hi Chuck,

This is certainly a noiseless image. The available dynamic range is largely
unused: all the information is hold by a small segment between 0.0007 and
0.0124 in the normalized [0,1] range. This is also quite oftenly found in
CCD astroimages. However, this image has virtually infinite SNR regardless
of dynamic range usage, which is not precisely what happens with astrophotos
of any kind.

Here is my try:

FITS format, 16-bit unsigned integers (1.23 MB):
http://pleiades-astrophoto.com/tmp/pi-test-images/200406161520-pi.fit

JPEG format (316 KB):
http://pleiades-astrophoto.com/tmp/pi-test-images/200406161520-pi.jpg

Processed with the latest beta of our PixInsight. Only a single histograms
transform and a wavelet transform (à trous algorithm with deringing).

This is the raw 16-bit histogram shown with 64x horizontal magnification.
The stretch points are enclosing the nonzero segment. The histogram is
filled with gray because of gaps, i.e. unused steps:
http://pleiades-astrophoto.com/tmp/pi-test-images/raw-16bit-histogram.jpg

And this is the whole histogram after processing, shown in the 12-bit range
(no gaps at all):
http://pleiades-astrophoto.com/tmp/pi-test-images/final-12bit-histogram.jpg

An illustrative example.

Regards,

Juan

-- 
-------------------------------------------------
Juan Conejero, Pleiades Astrophoto
juan.conejero_at_pleiades-astrophoto.com
http://pleiades-astrophoto.com/
-------------------------------------------------

----- Original Message ----- 
From: "Chuck Vaughn" <aa6g@aa6g.org>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Thursday, June 24, 2004 4:37 AM
Subject: [APML] Process this Raw Image


> Guys,
>
> Since we've been discussing noise in images, I though I'd offer up this
> image for processing. This is about as close to a noise-free image as
> I'm likely to see.
>
> http://www.goldrush.com/~aa6g/Images/200406161520.raw  (1.3MB)
>
> This is a 10 bit image stored in 16 bit format. Here's what you need to
> know to open it:
>
> 802x802 pixels, 1 channel, 16 bits, IBM byte order, no header.
>
> To get you oriented, that is White Sands, New Mexico at the bottom
> center. This will show you what a noise-free image looks like and how
> much you can process it, even after conversion to 8 bits. You'll run
> into posterization before you'll see noise. ;-) Compare the (lack of)
> noise to a typical film astrophoto or even a decent 16 bit CCD image.
>
> My stab at it is located here:
>
> http://www.goldrush.com/~aa6g/Images/200406161520.jpg  (192KB)
>
> Many of you will have to zoom it to 200% to see all the detail when you
> finish it.
>
> This is also an example of what the CCDers mean when they say they can
> enlarge their images by 2x or 3x for printing. This image is best
> viewed as a print at 75 - 100 dpi.
>
> Have at it!
>
> Chuck


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