Re: [APML] OT: Nikon D2H Astrophotography Tests

[Jerry Lodriguss <jerry@astropix.com>]

Hi Rob,

I think I have read that although the color is interpolated, the 
information is correlated because it is derived from samples at the actual 
pixel locations, and is almost lossless.  I think I read this in a Kodak 
technical publication, but I can't remember where.

Jerry


At 06:32 PM 1/4/2004 -0500, you wrote:
>Jerry,
>Below is a paraphrase by Terry Platt explaining his one shot color camera.
>I believe it applies to most one shot color digital cameras on the market.
>
>"Most digital cameras use a CCD with a built-in Bayer matrix of red, green
>and blue filters, directly deposited onto the CCD surface. The matrix is
>decoded
>to red, green, blue and luminance data by the software and gives a
>resolution
>which depends on the decoding algorithms. The optimum processing gives a
>luminance resolution of about 70% of the pixel resolution, so resolution is
>down, but not dramatically so.
>Colour matrix CCDs are a compromise between resolution and simplicity, but
>make colour imaging a good deal easier and quicker. Virtually all digital
>still cameras use the same principle."
>
>Rob Gendler
>Email: robgendler@att.net
>Web site: http://www.robgendlerastropics.com/
>----- Original Message -----
>From: "Jerry Lodriguss" <jerry@astropix.com>
>To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
>Sent: Sunday, January 04, 2004 3:02 PM
>Subject: Re: [APML] OT: Nikon D2H Astrophotography Tests
>
>
> >
> > >
> > >Nice review. That must have been alot of work.
> >
> > Hi Rob,
> >
> > A little bit more work because I had to manually trip each exposure and
> > they were only a couple of minutes each. Not like just opening a 60 minute
> > exposure on film and then taking it easy for an hour. <G>
> >
> >
> >
> > >Because of the way these cameras acquire color ( not all the pixels
> > >are used at once) they will not have the same resolution as the
>monochrome
> > >astronomical CCD cameras.
> >
> > I'm not quite sure what you mean when you say not all the pixels are used
> > at once, this is not my understanding of how the Bayer pattern cameras
>work.
> >
> > I've read that the resolution is the same for the luminance data, where
> > each pixel is used, but that the color data is what is sacrificed, and
>even
> > then, it's a pretty clever algorithm that is used to reconstruct the
>color.
> > Of course, there is no arguing that these consumer digital cameras are
> > vastly inferior to a dedicated cooled CCD astro camera in a lot of other
>ways.
> >
> > On the other hand, they do have their advantages, such as price and sensor
> > size/pixel density.
> >
> >
> >
> >
> > >Also the blue halos and distortion of the stars
> > >are more likely due to the performance of the 400MM F2.8 lens. These
>lenses
> > >are not apochromatic or even close.
> >
> >
> > Yes, I tend to agree with that.   On the other hand, this performance is
>so
> > bad, I really have to wonder if something is wrong with the lens, or if
> > something else is going on (perhaps bad focus too).
> >
> >
> >
> > >CCD's will bring out all these optical
> > >flaws.With film the optical flaws of these lenses are masked by the
> > >overall low
> > >resolution
> > >of the image.
> >
> > Now I don't think that is true. I've seen this exact same kind of poor
>lens
> > performance with a 300/2.8 ED Nikkor on shots taken on E200 film.
> >
> > Both the 300 and 400 are the latest Nikon models too.  I didn't think it
> > was possible for my opinion of Nikon to get any worse, but even despite
>the
> > promise of the D2H, it has.
> >
> > Jerry
> >
> >
> >
> >
> > Photoshop for Astrophotographers - http://www.astropix.com/PFA/PFA.HTM
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
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>
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