[opendtv] Re: MPs back Ofcom stance on spectrum sale
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 28 May 2007 12:49:13 -0400
At 6:33 PM -0400 5/25/07, Manfredi, Albert E wrote:
By source detail limitations, I assume you mean with current HDTV
cameras, right? I would assume that current HDTV cameras are probably
limited to what the manufacturers think they can sell, at an attractive
price, to meet the needs of either 720/60p or 1080/60i. So my thinking
all along has been that arguing that cameras are not good enough for
1080/60p is a bit or a circular argument.
It's just the laws of physics Bert.
Oversampling sensors have a cost.
Lenses with good MTF and adequate performance for 1080P have a cost.
And shooting at 1080P has a cost in terms of lighting requirements
and the F-stops penalty.
We are already seeing a wide range of performance in products that
claim to deliver ANY of the HDTV formats. We are seeing MANY products
that use UNDERSAMPLING sensors for both 720P and 108024P/30i.
We are seeing complete cam/corders that sell for $5,000, while good
HDTV lenses can easily cot more than $20,000.
And then there is practical reality. As we increase camera resolution
we can gain additional detail, but only in the higher frequencies
that are typically less important to the human visual system. What we
gain is more contrast in the lower frequencies that do matter to the
human visual system. The GOOD NEWS is that we can deliver better MTF
with a lower resolution format when we oversample.
So for the foreseeable future every gain for 1080 line cameras is
going to make 720P emission look better. In the end, this thread is
not about camera quality. It's about delivering higher quality HDTV
to the masses, and you can't get there by stressing the distribution
system to deliver more samples with lower quality.
I think Mark Schubin indicated that new cameras are available now with
sensors the size of 35mm movie film frames (18mm X 24mm). That should
take a lot of cost out of the lens, and should make those cameras good
candidates for 1080p acquisition.
No, it increases the cost of the lens. It also makes it possible to
use many of the prime lenses now used with film cameras, but this
does not reduce cost, it just leverages existing investments in
lenses in Hollywood. You might want to look into the issues related
to build high quality zoom lenses for larger sensor sizes - the costs
are VERY significant.
The transmission channel should become adequate as well. Whether or not
broadcasters will use it for 1080/60p transmission will no doubt depend
on where consumers go with their future TV purchasing habits. Certainly,
comparing what consumers are doing today, with what they were doing in
1995, should give anyone pause.
You keep saying this, but we are still a LONG LONG way from having
compression efficiency that can DELIVER the extra detail in 1080@60P
with enough headroom for the peak bit rates needed. And the program
distributors are NOT going to waste bits trying to serve the upper 2%
of the audience.
Regards
Craig
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