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Posted by Toby on 10/04/62 11:42
"Bill Fright" <billfright@austin.rr.com> wrote in message
news:SEdSf.2152$1Z5.1191@tornado.texas.rr.com...
>
>
> PTravel wrote:
>> "Everyguy" <everyguy@Nospam.com> wrote in message
>> news:GmWRf.1766$HW2.420@newsread3.news.pas.earthlink.net...
>>
>>>I notice that if I limit DVD's of home video to 1 hour, the quality is
>>>considerably cleaner. The graininess that shows up in certain areas at
>>>times
>>>in the longer DVD - basically go away. Some people might not even notice
>>>the
>>>difference but I do.
>>>
>>>So why is it a commercial DVD can contain a complete movie plus whiz bang
>>>graphics and "extras" and still look very sharp, even on a computer
>>>monitor
>>>which I find generally has fuzzier resolution than a TV? Or even one of
>>>these "squeezed" DVD's on a CD with a full length movie can still look
>>>very
>>>good, with obviously far less data?
>>>
>>>Is it that the master they're working from is so much sharper it can take
>>>more degradation, or the process they use to compress the video, or...?
>>>
>>
>>
>> First of all, the source material on commercial DVDs is he
>> highest-quality (usually), which helps.
>>
>> However, the big difference is in transcoding to mpeg2. Proper
>> transcoding takes multiple passes -- each frame must first be analyzed in
>> sequence and, only after the analysis has been performed, actually
>> compressed. Consumer software transcoders, such as are found in many
>> low-end editing and DVD authoring programs, are optimized for speed,
>> rather than quality. DVD camcorders and low-end computer capture cards
>> that capture direct to mpeg do single-pass encoding on-the-fly and
>> produce poor quality transcodes.
>>
>> There are consumer alternatives, however. I transcode using tmpgenc, a
>> standalone program. Tmpgenc is very "tweakable" and, at its
>> highest-quality settings can approach commercial DVD quality with good
>> source material. The downside is, it's very slow. A 2-hour video can
>> take up to 24 hours to transcode with tmpgenc on my 3 .1GHz P4 machine.
>> However, the results are worth the extra time, in my opinion.
>>
>>
>>
>
>
>
> Let's not forget the glass. My town is swamped by the film festival crowd
> right now and I saw someone with one of those little Panasonic 100A
> looking cameras with a big HD on the side. It cracked me up because the
> lense was comparible to what's on my phone.
>
> Fine lenses are huge for quality images.
Of course the glass makes a difference, but first comes the sensor size.
1/3" imagers require lenses of much shorter focal length to get the same
coverage than do professional 2/3" chips, and by the laws of optics to
achieve a max aperture of, say, f1.6, a lens of half the focal length
requires a front element only 1/2 the diameter. Another factor is the
magnification--most of the little cams only have 10x optically, compared to
15-22x for pro lenses. So mostly pro lenses are so big because they need the
front element diameter for a low f stop at long focal lengths. That being
said, of course it is easier to do optical correction on larger lenses, but
no one spends money correcting a lens past the actual resolution of the
imager.
Toby
>
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