"fschwamm" <ich@frank-schwamm.de> wrote in message

news:724a6a7a.0404260902.c39b002@posting.google.com...

> my problem is, that some people told me, that the full number of

> pixels is only used for getting the still photographs, which would

> mean that the video mode digital zoom is based entirely on the 400000

> or so pixels "standard" video resolution so that - take the extreme -

> a 100x digital zoom would leave me with a 4000pixels image and not a

> theoretically possible 10000pixels image given a 1mpixel chip (not

> that it would help much in this case, but just in principle :) ). To

> put it differently: if the camera uses it's full megapixel capability

> in video mode i should be able to get a 2.5x digital zoom without any

> loss of resolution given a 400000 pixel video resolution.

>

> my point is: is it worth buying a multi-megapixel camcorder, although

> i don't intend to use it as a digital camera, i.e. is there a

> camcorder with which i could get a loss-free say 25x zoom although the

> lens only provides an e.g. 10x optical zoom.

>

> frank

This comes up often, and the answer is that the motion-video *can*

make use of more than the basic 345K (NTSC) or so pixels that

would be needed for straight mapping of pixels from the CCD to

the output (which is not done - the analogue output is a "bandwidth",

not a pixel-count...). These "extra" pixels can be use for increased

effective resolution and color info (a 3-CCD camera, BTW, uses

3x345k for "full" color info and resolution - so presumably a 1-CCD

camera could make use of a megapixel image area for motion-video

and still not be "throwing away pixels" even if it directly mapped

the pixels to the output, which it doesn't [and add overhead and area

used for stabilazation, and the count grows considerably...]). If the

camera is designed to make use of the higher pixel count for

motion-video (likely), then reducing it with the use of the digital

zoom would likely still show image losses, even if the final area uses

at least 345k pixels. Unfortunately, increasing pixel count without

correspondingly increasing the sensor area generally results in

lowered sensitivity and possibly more image noise and increased

tonal problems...

--

David Ruether

d_ruether@hotmail.com

http://www.David-Ruether-Photography.com