[opendtv] Re: Image quality
- From: Mark Schubin <tvmark@xxxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 13 Nov 2005 12:51:21 -0500
Tom Barry wrote:
> <>Still, it seems it would be a mathematically simpler problem to just
> deal with the distortion caused by limited optics.
If you know the distortions AND you have enough dynamic range, sure.
But the reason a crew was sent to repair the Hubble telescope instead of
simply sticking a computer on the output is that sometimes you don't
have enough dynamic range.
In Larry Thorpe's paper presented at SMPTE on Thursday, he showed charts
of camera-limited MTF for various formats. The 2/3-inch 1920 fell to
about 45% MTF at 872 TV lines per picture height (30 MHz, 1550 lines
across). That's a little more than one bit down from 100% MTF. The
1/2-inch 1440 looked to be about 25%, or two bits down. The 1/3-inch
960 looked to be about 6%, or about four bits down. Another one of his
slides compared the same lens configured to create 2/3-inch, 1/2-inch,
or 1/3-inch images. At 872 TVLPPH, the 2/3 was about 75% MTF, the 1/2
was about 55%, and the 1/3 was about 28%. That's another big chunk of
dynamic range lost.
TTFN,
Mark
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