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Thread: DVR/rec refresh rates

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    Default DVR/rec refresh rates

    Is it rite to say if I get a 16ch DVR, though only want to fit 8x 540 TVL 1/3 3.6mm camera's, I can record at a higher refresh rate since I'm not using all the channels of the DVR?



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    higher frames per sec of recording I mean.

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    I cant comment on Aussie DVR's but here in the uk in depends on wether the dvr has a fixed frame rate per channel or if its combined framerate for the whole DVR.

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    Quote Originally Posted by imaz View Post
    higher frames per sec of recording I mean.
    Yes but you will be paying for it. There is a big price jump between 100fps , 200fps & 400fps global DVRs. The fps is usually a global spec so in theory a 200fps DVR will run one camera at 200fps , two cameras at 100fps each or four cameras at 50 fps each. Some machines can be set on a chan x chan basis. For smooth motion don't go below 18fps

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    As the PAL standard specifies 25FPS, that's the max most DVRs allow for per channel. With a global frame rate of 400FPS on a 16ch machine, that equates to 25FPS per channel or what's referred to as 'Real Time'.

    Most DVRs now offer 'Real Time' recording, however the cheaper models limit this to CIF resolution (352×288 PAL). To take advantage of the available resolution from most cameras, you really should be looking to record at 4CIF (704×576 PAL) or D1 (720x576 PAL). With most DVRs, this will equate to a reduction in frame rate to 5FPS per channel max. Although some will argue differently, I'd rather have 5 decent images than 25 images lacking clarity and detail.

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    [QUOTE=Drift;25FPS per channel or what's referred to as 'Real Time'.

    [/QUOTE]

    Tho you can go to about 18 fps before you "see" a difference.

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    Quote Originally Posted by watchdog View Post
    Tho you can go to about 18 fps before you "see" a difference.
    A little subjective IMHO. Depends on the FOV and the subject it's self. That said, personally I find anything over 12.5FPS a waste in all but the most critical of applications and even then you'd have to have a pretty good argument to convince me otherwise.

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    That's why I dread the inevitable question " How much storage time will I get"

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    If you record in CIF, and with a camera 1/4, 3.6mm, 420TVL, can you see a persons face clear enough to ID?

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    Quote Originally Posted by imaz View Post
    If you record in CIF, and with a camera 1/4, 3.6mm, 420TVL, can you see a persons face clear enough to ID?
    Why would you use a 1/4" sensor when you want clarity?
    3.6mm is fairly wide so they would need to be pretty close.
    I'm sure I've read somewhere that for legal ID you need to have the head take up 3/4 of the picture.

    So if it is poor light then - no
    If it is a poor angle then - no
    If it is out of focus then - no
    If they have a hoodie on then - no
    If they have sunglasses on then - no

    It matters little HOW you are recording if the picture presented to the recorder is shit.

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    Would you like zoom and enhance with that?

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    Ikegami 1/2" CCD with 50mm Lens is what I use for Entry ID shots. I can print passport photos with the quality.

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    Seriously, for the typical domestic home use. What would you use for the below:-

    All external:-
    1) Portico
    2) Courtyard (dark area, no lighting at night) which joins to portico.
    3) Side of house (length is 30m and narrow) - No exits here from inside the house, but a side gate.
    4) Rear overlooking alfresco which is sliding entry.

    Initially I was looking at getting all 3.6mm wide dome 1/3 540TVL and mount all these at the tip of the eves. My guess is these camera's wouldnt be viewéd unless there was some kind of suspicious act and then I could review them to some degree.
    Last edited by imaz; 14-04-11 at 02:41 AM.

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    4-9mm or 3.5-8mm 1/3" Sony CCD 540TVL vandal resistant IR domes at a minimum. The 30m side may benefit from 2 cameras depending on PQ (paranoia quotient). Don't mount them to the eaves either unless you've got 4 solid fixings into beams. Best mounted to a brick wall where possible.

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    Quote Originally Posted by imaz View Post
    My guess is these camera's wouldnt be viewéd unless there was some kind of suspicious act and then I could review them to some degree.
    So you're not setting up a control-room in your bedroom?

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