Thanks to David and Tyler. Will check out flexure as possible cause of image shift while using the autoguider. I have in the past used eyeball guiding with a second scope and I am in the habit of bolting everything together as tight as possible but SCT mirror movement is a possibility as is flexure. In regards to my JPEG binning question; Large says 3888X2592 pixels and Medium says 2816X1880 pixels. What have they done to give a smaller pixel count? That ratio is 0.724. Does JPEG 'chuck' pixels, change bit depth and call it a change in pixel count or what? Again just curious and can't seem to Google an answer. Now with some off and on clouds in S UT I'll spend some time processing a couple of images. Shot M-8 using a Pentax 67 200 mm f4 lens coupled to the EOS 40D at ISO 800. Thanks again, Steve
Stephen: When you change image size to make it something less than the cameras full image size you are in fact "chucking pixels". Each camera has a fixed numbers of Micro lenses resulting in a maximum image size or number of pixels. If you shoot smaller than that the Camera's maximum size the camera has an algorithm it uses to re-size (chuck pixels) to give you the size image you are requesting. Bit depth does not change, just pixels. The full size images enlarge better and print much better as there is more detail information or resolution (more pixels making up the image) but if your end result is destined for a computer screen resolution doesn't have to be that high. Computer screens, even good ones, are almost always far below what your camera can produce or resolve. Short answer: Yes, pixels are chucked. Bob -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Stephen Peterson Sent: Sunday, November 07, 2010 9:52 AM To: utah-astronomy@mailman.xmission.com Subject: [Utah-astronomy] Photo questions Thanks to David and Tyler. Will check out flexure as possible cause of image shift while using the autoguider. I have in the past used eyeball guiding with a second scope and I am in the habit of bolting everything together as tight as possible but SCT mirror movement is a possibility as is flexure. In regards to my JPEG binning question; Large says 3888X2592 pixels and Medium says 2816X1880 pixels. What have they done to give a smaller pixel count? That ratio is 0.724. Does JPEG 'chuck' pixels, change bit depth and call it a change in pixel count or what? Again just curious and can't seem to Google an answer. Now with some off and on clouds in S UT I'll spend some time processing a couple of images. Shot M-8 using a Pentax 67 200 mm f4 lens coupled to the EOS 40D at ISO 800. Thanks again, Steve _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
participants (2)
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Robert Taylor -
Stephen Peterson