Thanks for a nice post!

On Sat, 5 Oct 2002 23:04:16 -0500, "JD" wrote:

>
>"Supreme Enchanter" wrote in message
>news:HgJn9.25408$YK4.2636402@e3500-atl2.usenetserver.com...
>> You loose them. DVD has around 500 lines of resolution while broadcast
>> quality is 780. Easy question. Easy answer.
>>
>Summing up my message below:
> The limiting horizontal resolution of the normal digital
> formats (broadcast and consumer DV) is the same. It really doesn't
> make any sense to claim that BQ is 780TVL, when DigiBeta can do
> only 540TVL. You might be confusing pels (720H) and TVL (which
> is pels / (aspect ratio).
>
>
>For TVL resolution, all of DigiBeta, DV25, DV50, DVCPRO, DVCPRO50, DVD, and
>DVCAM each have 720 samples per line (pixels.) When normalizing this
>digital sampling resolution to a per-picture height basis, then the limiting
>resolution is 540 lines. There are numerous kinds of 'resolution', and
>the amount of 'information density' that can be accurately reproduced
>is different amongst the various formats above, in each of the Horizontal,
>Vertical, and time domains.
>
>Some of the different formats can sometimes start rolling off before
>the 720 pixel limit because of tradeoffs to minimize the DCT truncation
>artifacts. Along with the format limitations, there are also camera head
>and lens limitations. You might find that some cameras will start rolling
>off in the horizontal and/or vertical directions sooner than the 540TVL
>(or 720 pixel) limiting resolution. A really good camera wont roll off
>until a significantly higher resolution level (in both the horizontal and
>vertical directions) than a consumer camera. Consumer and lower end
>professional cameras have only 1pel per horizontal scan line, and this
>takes away some of the flexibility to provide both high vertical resolution
>and mitigate interline twitter. Better CCD arrays can provide 2 pels per
>horizontal scan line, and can provide a sharper rolloff in vertical
>response that stretches more vertical resolution while providing good
>interline twitter reduction.
>
>When trying to force too much vertical detail (not just horizontal detail) through
>a narrow bitstream (and using the DCT truncation/redundancy elimination),
>you'll get mosquitos, stairstepping and other ugly effects. DV50, DigiBeta
>(and of course, uncompressed D5) don't produce those ugly effects as
>easily, because of much less digital truncation and roundoff. The differences
>are mostly the differing amounts of artifacting, and not basic resolution.
>
>Frankly, given a 'testpattern' like the SMPTE resolution chart, or a
>multiburst pattern, those don't really provide much of an information
>density test demonstration. Each of teh above formats should be able
>to reproduce the static low density static images nearly perfectly up
>to approx the same resolution. Where the higher end formats become
>superior (e.g. DigiBeta or DV50) is the ability to handle lots of complex
>detail (and significant differences between the fields of a frame.) Lots
>of 'regular' detail as shown by a test pattern is fairly easy for all of
>the common formats.
>
>>
>> BTW: If you are only going
>> to DVD, get a DV or Mini DV cam ($3000) vs a broadcast quality cam
>> ($20,000). You'll get 520 lines of resolution which is better than DVD. I
>> mean a corporate grade camera and not a consumer grade.
>>
>DVD can provide 500 TVL of resolution, little or no different in horizontal
>resolution terms from DigiBeta (high end broadcast) and DV25 (the
>traditional DV format.) The differences in the visual quality of the
>formats is more related to their abillity to deal with alot of detail
>without artificating (and with MPEG2 schemes like DVD, the redundancy
>elimination is more dependent on temporal compression also.) DV
>does have an aspect of temporal compression, but only on a 2 field
>basis. (Detail and resolution aren't the same thing!!!)
>
>Again, the RESOLUTION differences are based more upon the camera
>head quality. The camera head resolution only has to provide 720pels
>flat to fit the best of the digital formats. Even a good quality consumer
>camera can likely provide 450-480TVL limiting resolution, but would
>start rolling off before then. A good quality broadcast camera might
>provide 600-700 TVL of true limiting resolution (perhaps a little
>more), but the important aspect of that resolution is the rolloff
>characteristic.
>
>So, the consumer camera and the professional camera don't make
>a major difference in end result because of lots higher limiting
>resolution, but the detail might be better/cleaner because
>the professional camera rolls off
>less at the maximum useful resolution of 540TVL.
>
>John Dyson