Re: 680k Pixel MiniDV w/340K Effective Pixels for a MiniDVCamcorder
- From: "Gene E. Bloch" <hamburger@xxxxxxxxxxxxxxxx>
- Date: Mon, 03 Oct 2005 16:44:33 -0500
"PTravel" <ptravel88-usenet@xxxxxxxxx> wrote in
news:3q37n0Fd30seU1@xxxxxxxxxxxxxx:
>
> <allr1@xxxxxxxxx> wrote in message
> news:24682-433C590F-31@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> PTravel wrote:
>>
>> " miniDV resolution is 720 x 480 pixels (NTSC) for a total of
>> 345,600 pixels, i.e. approx. 340k.
>>
>> ^^================================^^
>>
>> The info I found on the JVC camcorder said that the video
>> resolution is 640 x 480. That
>> may be the resolution of what the tape can record and not the
>> camcorder itself.
>
> It's not. I'm not familiar with the JVC camcorder. However,
> miniDV is a standard that uses 720 x 480 pixels for NTSC video
> (which is the standard used in the US). If the camcorder can't
> generate a digital video stream that is 720 x 480, it doesn't
> conform to the standard. This means that (1) it will have reduced
> resolution, and (2) you may have trouble editing it. 640 x 480 is
> the VGA standard, and a lot of media software and hardware can
> handle it.
>
> Video resolution encompasses two separate aspects -- the number of
> pixels per frame, e.g. 720 x 480 or 640 x 480, and the extent to
> which fine detail can be resolved, measured in horizontal and
> vertical lines per inch. The two are related, but the fact that a
> camcorder has 720 x 480 pixels does not necessarily mean that it
> can resolve fine detail well. The number of horizontal by
> vertical pixels only describes the digital format of a frame. The
> lines-per-inch resolution measures the actual resolving power of
> the system, and is a product of the quality of the lens, the
> accuracy of focus, the dynamic range of the sensor, and the
> ability of the electronics to exclude noise.
>
> As I mentioned in my earlier post, the miniDV allows for a
> theoretical maximum horizontal resolution of 525 lines per inch.
> However, most low-end consumer miniDV camcorders will not approach
> this. A 640 x 480 camcorder sounds like a real cheapie -- I
> wouldn't expect much from it.
>
>
>>
>> I have a Hi-8 camcorder now, but if I use it for shooting video
>> of anything that's farther than
>> 50' away (w/o zoom) the subject is very grainy and hard to see.
>> (what's recorded on tape)
>
> What you've described relates to the horizontal and vertical
> resolution, i.e. how many lines per inch your camcorder can
> resolve. There are many, many factors that effect resolution.
>
>
>> I'm hoping that miniDV's better resolution will be able to handle
>> objects that are farther away.
>
> As I said, the theoretical maximum resolution of miniDV exceeds
> that of the theoretical maximum of Hi8 -- 525 lines per inch
> versus 450 lines per inch, respectively. However, these are only
> theoretical maximums.
>
> I have an old Sony TR-600 Hi8 camcorder. This was a
> close-to-the-top-of-the-line consumer camera Sony manufactured 10
> or 11 years ago. It has better resolution than many low-end
> consumer miniDV camcorders that are on the market today. However,
> I also have a Sony VX2000 miniDV camcorder. This is a prosumer
> model that produces high quality video. Sony claims that maximum
> resolution, i.e. 525 lines, for this camera, and I have no reason
> to disbelieve that.
>
> To answer your question, a cheap consumer miniDV camcorder will
> not necessarily have better resolution than your Hi8 camcorder,
> and may have dramatically poorer resolution. It will also,
> undoubtedly, have far poorer low light performance (though that's
> another discussion entirely). As I said, there are miniDV
> camcorders on the market that barely achieve VHS resolution (250
> lines per inch or so). Merely switching formats does not ensure
> that you'll get better resolution.
>
>
>
>>
>>
>> PTravel wrote:
>>
>> " Camcorders that have higher density sensors usually use them
>> for still imaging. Some (but, generally, not bottom-of-the-line
>> machines) can do pixel subsampling, i.e. using the additional
>> pixels to "average," producing a slightly better image. "
>>
>> ^^================================^^
>>
>> Yes, the info on the JVC said Image resolution (still, as opposed
>> to video) is 1024 x 768.
>
> Still resolution is meaningless to video resolution, except that
> higher density sensors tend to have poorer low-light capability
> and introduce more artifacts to the video.
>
>
>>
>> It also mentions that the JVC uses a 'super high-band processor
>> that restores the high-band components of the luminance signal to
>> ensure a crisp picture with 520 lines of resolution' for video.
>
> 520 lines would be great. I don't believe it, though, if the
> video resolution is 640 x 480.
>
>>
>>
>>
>>
>> PTravel wrote:
>>
>> " Resolution is a different issue that is not necessarily related
>> to the number of pixels on the sensor. Hi8 was capable of around
>> 400-450 lines per inch. MiniDV, in theory, is capable of up to
>> 525 lines per inch. In practice, however, you will not reach
>> those kinds of resolutions which cheap consumer equipment.
>> Maximum resolution is a function of optics and electronics, as
>> well as sensors. A 340k sensor machine, theoretically, could
>> reach 525 lines, but a cheapie consumer model almost certainly
>> won't -- I've heard of some consumer camcorders that resolve as
>> little as 275 lines, which puts them in VHS territory. "
>>
>>
>> ^^===============================^^
>>
>> Well it looks like 340K effective for video is normal for a
>> low-end miniDV camcorder.
>
> 340K isn't "normal" -- it's what's required to produce a 720 x 480
> image. My VX2000 has ccds with 380k pixel sensors, though it has 3
> separate CCDs, one for each primary color.
>
>
>>
>>
>> 2 more question come to mind:
>>
>> 1) What video resolution is considered 'broadcast quality'?
>
> I'm not sure if there's an actual standard, though there may be.
> Broadcast-quality monitors usually resolve 600-700 lines.
>
>>
>>
>> 2) Does miniDV and Hi-8 tape record video at less resolution than
>> the camcorder is capable of? (I've recorded the Hi-8 camcorder's
>> signal directly into a DVD recorder and it seems to yield a
>> better picture than what plays back on the Hi-8 tape)
>
> I'm not quite sure what you're asking. As I said, resolution is
> the result of the particular combination of lens and electronics,
> as well as the particular standard employed. The Hi8 format can
> accomodate up to 450 lines per inch, but very few camcorders are
> going to reach that. However, some do. The miniDV format can
> accomodate up to 525 lines per inch, but very few camcorders are
> going to reach that. However, some do.
>
> As for getting better results taking the analog video signal from
> a Hi8 and recording it to a DVD recorder, there are so many
> variables that it's impossible to say what's happening. Analog
> signals must be digitized to make a DVD. The digitization
> process is done by the DVD recorder in realtime. The resulting
> digitized video is then compressed to DVD-compliant mpeg2 and
> written to the DVD. Mpeg2 compression is a black art that is
> dependent on the particular software employed. Frequently,
> consumer-grade DVD-compliant mpeg2 video transcodes look soft --
> this is done to repress digital artifact that result from the
> conversion of analog to digital. Many people prefer a softer
> picture to a picture filled with jaggies and other digital
> artifacts. This may result in a subjective judgement that the
> picture is "better," but it really isn't.
>
> MiniDV camcorders perform the digital conversion internally. They
> output a digital video stream (and some of them can also output
> analog video as well). Again, the quality of the video is going
> to be dependent on all the components that make up the camera --
> lens, sensors, electronics, etc.
One correction is necesary here. The resolution is in lines, not
lines per inch. That is, lines per picture. (More or less; there is
a convention, which I forget, in expressing the horizontal
resolution.)
Consider that you might be showing the tape on a 12" TV and I might
be using a 24" TV - or vice versa... Surely you don't believe that
the picture on the smaller TV shows around 5000 lines in its roughly
10" height, while the other shows around 10000 lines.
Regardless of the resolution of the picture, miniDV tape has a fixed
format with 720x480 pixels (NTSC), so a source containg a different
number of pixels is interpolated or extrapolated to fit.
HTH,
Gino
--
Gene E. Bloch (Gino)
letters617blochg3251
replace the numbers by "at" and "dotcom"
.
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