From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


Jeff, I've been using a NTSC camera for my testing and when you pretty much
fill the screen with the optic, the resolution is more than good enough.
The latest Harbor Freight flyer shows a video camera setup for only $30
which will be a fairly decent price for a camera. If you use a digital
camera, you will lose the dynamic feedback you get with a video camera but
that could also be a detriment, depending upon what the purpose is.
Don't denigrate the JPG compression data loss too much.  I was part of one
of the companies that generated the standard and I have a demo program from
that company on my websites (name is Alice) that does JPEG compression on
images.  It isn't until you really start crunching the image down that you
start losing any of the low frequency info which is part of the desired
info on an image for foucault reduction.  It is the high frequency data
that gets lost first and even that is fairly minimal at the lower
compression ratios that the cameras use.  Getting a hundered bit flips
(change of 1 pixel by one count in one of the colors is a bit flip) is
pretty indicative of a minimal change to the image.
Unfortunately, I don't think that I still have the image comparison program
on hand but that would show how much compression affects an image and from
the results obtained back then, it really isn't much until you start really
high compression ratios that you can see things.  I will note that Alice
does a sort of primitive comparision when you change the compression rato,
the new image overlays the old compressed image and you can see the changes
that way.
Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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