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#17716 - 01/18/07 11:38 AM PIxel Information
Anonymous
Unregistered


Hi, im at a loss here and need help.

I have a CCD camera and I want to get each pixels intensity so I can have a 3-d plot of (x,y,intensity) to get a proper image of my output.

Nobody seems to know how
Any help??


Dave

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#17726 - 01/18/07 07:33 PM Re: PIxel Information [Re: ]
DA Morgan Offline
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Registered: 10/17/04
Posts: 4136
Loc: Seattle, WA
Put the data into a computer and deconstruct the bitmap.
_________________________
DA Morgan

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#17732 - 01/18/07 08:42 PM Re: PIxel Information [Re: DA Morgan]
dr_rocket Offline
Member

Registered: 12/06/06
Posts: 196
Loc: Palo Alto, CA, USA
Hi odwyerda,

Like DA says most CCD cameras will generate jpeg (which is short for Joint Photgraphic Experts Group)image that can be downloaded to you computer. But that is not what your asking for. Let's see if I can make this easy.

The problem with jpeg for anything scientific or the like is that jpeg images use what is known as "lossy compression. "Lossy compression" means just what it says. Enough information is extracted from the raw data to create the jpg file. There is enough information in the jpeg file to recreate the image on your screen or printer. (If you know about the Nyquist sampling theorem this will make more sense.)

Astronomers, amateur and professional, use CCD arrays (and other similar gadgets) all the time. These people want every scrape of information that they can get. They use a gadget called a frame-grabber. Such a device will give raw data from the imaging array. This page contains lots of links on the subject:

http://www.pacificsites.com/~brooke/ACCD.shtml

This stuff is all marketed toward the amateur astronomer and is commercially availabe.

I hope that this is useful for you and good luck.

Dr. R.

P.S. I'm having difficulty spelling today.


Edited by dr_rocket (01/18/07 08:46 PM)

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#17745 - 01/19/07 06:38 AM Re: PIxel Information [Re: dr_rocket]
DA Morgan Offline
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Registered: 10/17/04
Posts: 4136
Loc: Seattle, WA
Correct Dr. R. ... but at the same time it should be noted that some cameras allow downloading, not as JPG, but as BMP.

For example:
http://store.starrynightstore.com/maxdslr.html
_________________________
DA Morgan

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#17788 - 01/21/07 06:11 PM Re: PIxel Information [Re: DA Morgan]
dr_rocket Offline
Member

Registered: 12/06/06
Posts: 196
Loc: Palo Alto, CA, USA
Hi DA,

Quite true, but the format of the image file is irrelevant. Odwyerda is asking about accessing the pixel intensity. It seems that what s/he wants is a 2-D array of numerical values that the CCD array is working with.

The ability of a digital camera to export different file formats, e.g., FITS, TIFF, JPEG, PNG, or BMP, resides more in the software that comes with it than in the camera. (Of course there is more than one way to skin a cat.)

As the case may be going from the collector array to image file is a form of "image processing." In all these cases the process is, to some degree, lossy since there are D to A and A to D conversions. These introduce, if nothing else, aliasing.

By the way a BMP file is not so simple as many assume. Multiple ways of storing information are allowed. Indexed color mapping vs various RGB encodings and RLE compression are supported. (Of course, no one uses all the capabilities of a BMP.) A BMP is not a pixel for pixel reproduction of the CCD array.

Dr. R.


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#17800 - 01/22/07 04:02 AM Re: PIxel Information [Re: dr_rocket]
DA Morgan Offline
Megastar

Registered: 10/17/04
Posts: 4136
Loc: Seattle, WA
Correct mon ami. Perhaps I am making an incorrect assumption here but I am operating on the basis that odwyerda is an amateur astronomer as a professional, such as my step-daughter, would have access to the information directly.

And, again perhaps incorrectly, that an amateur would be able to use the info recorded in the camera image to meet their needs.

I am looking forward to moving to an area with black skies in a few years, not sure where, and hope to get myself a 16-20 inch Richey-Chretien and take a few pics myself.
_________________________
DA Morgan

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#17807 - 01/22/07 05:44 PM Re: PIxel Information [Re: DA Morgan]
dr_rocket Offline
Member

Registered: 12/06/06
Posts: 196
Loc: Palo Alto, CA, USA
Hi DA,

Astronomy was my first love - I was about seven - and it has not gone away.

Black skys? Sounds good to me!

Good Seeing!

Dr. R.

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