Hi--

http//www.David-Ruether-Photography.com/camcorder-comparison.htm

Hello, - there is a great need for communities to be able to protect themselves using cctv.

While it is possible to connect an analogue camera to a computer and capture cctv files directly to the hard drive (via a video capture card such as that offered by Geovision or Winnov) the problem arises of interlacing which causes the results to be "pixelated".

Would the use of a progressive scan camera avoid this problem of interlacing and could such a camera be used as an internal or external cctv camera?

I suppose it would be necessary to capture compressed video files - for example by using a Geovision card, one can capture handy 5 minute clips for a whole month using an 80 gb hard drive which means that recording can take place 24 hours a day for a whole month without having to worry about "changing tapes" as was the case when using video recorders.

The trouble is the resulting files have the interlaced effect which can make it difficult to clearly identify moving suspects.

If you can suggest any solution to avoid interlacing please let me know.

Yours faithfully,

JOHN AIDINIANTZ

www.londoncctv.com

I'm assuming that "cctv" refers to surveillance camera systems?

And that the object is to find a single frame, and use it (in the

highest possible resolution) for identity purposes? For this, a

progressive-scan camera would be preferable (though this will

result in poorer motion-rendering - irrelevant to your purposes,

I suspect...). PS-mode cameras vary considerably in the quality

of the PS-mode image, with some interpolating fields to get to

25/30 fps (probably unneeded by you - but I don't know what the

ideal frame-rate would be for your purposes [I would think a very

slow frame rate would aid in compression/recording-time, but if too

slow, it may cause the loss of important info...]), some properly

recording in PS mode, and some optimizing the PS mode image for highest

still resolution (these shoot at 1/12-1/15th second shutter, though...).

If the camera needs to be cheap, and maximum image quality is not

primary, the 1-CCD Canons can do full-frame-rate "full-res" PS-mode;

if half frame rate is OK, with higher resolution being useful (more

info to compress, though...), the megapixel 1-CCD Sony camcorders, or

for highest resolution, the 3-CCD VX2000, may serve best...

Ah, I just looked at your web-site...;-)

I'm not familiar with the characteristics of standard surveillance

cameras (whether PS-mode is available...). The cameras I'm familiar

with are Mini-DV, which can be connected to a computer through

analogue or FireWire (digital) means (the latter is a fixed-quality

system, so the former may serve your needs better...). BTW, most

1-CCD Mini-DV cameras have poor low-light range, but the Sony

models can be operated in infrared mode (preferably with "B&W"

selected), giving greater sensitivity - and illumination can be

provided by a nearly invisible IR light source. The cameras can be

modified to work in daylight, also, while in IR mode (see

www.David-Ruether-Photography.com/ir.htm - and search on www.google.com for info on the modification

procedure). Something like a Sony TRV25, modified to remove the internal daylight-IR defeat

switch, left in "Memory Stick" mode (which puts it in PS-mode - and

these will stay on if no tape is in place) may serve well, at moderate

cost...