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Another thing that is not being considered: when someone says a digital
image from a color digital camera is 6 megabytes they are really describing a 2
megapixel image with 3 bytes per pixel. Many CCDers make color images from
their files with R, G, & B filters and often use a luminance channel
too. So now we are talking about an image with 6-8 megabytes worth of
data. So, in comparing files sizes, make sure that one is comparing apples
with apples.
- Bill
----- Original Message -----
Sent: Tuesday, April 16, 2002 5:19
PM
Subject: Re: [APML] CCD/Film
Please understand I am not knocking CCD imaging. I use a very
high end $40,000 CCD camera in my business. These 2 MB files, that are
generated in astrophotography, are great when viewed on 72 dpi monitor or
printed out on an Ink Jet system. The fact is when printing an 8 1/2" x 11"
photo in a brochure on an offset press you need to have a file size of 25-30
MB at 265 dpi or the image will pixilate. There is no amateur CCD chip out
there that can generate such a file.
Larry McManus
on 4/16/02 12:57
PM, Chris1011@aol.com at Chris1011@aol.com wrote:
In a message dated 4/16/2002 1:33:09 PM Central
Daylight Time, lmcmanus@clearpointadv.com writes:
As I understand it CCD chips for astrophotography
generate
small file sizes (2 MB ). These are excellent when viewed on a
72 dpi
monitor but not good enough for full page 8 1/2" x 11"
reproduction
That's not really
correct. The latest chips produce images that cannot be adequately
reproduced on a typical 72dpi monitor. If you show them at full resolution,
you end up having to scroll a lot. We recently produced a 30x40 print of M42
taken with CCD cameras, where the smallest stars measure .060" and the
brightest about .22" diameter. This compares favorably with a print that
Tony Hallas sent to me years ago, also 30x40 of the Horsehead region taken
with 6x7 color print film. His smallest stars measure .050 and the largest
just under .25" diameter. One caveat, the CCD image was a composite of
narrow field and wide field instruments.
Roland Christen
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