CCTV - Technical Question

ironclaw

Hi Folks,

I'm currently updating my CCTV system. Its a 4 channel PC card with 380 line day / IR night camera's. So the obvious step up is an 8 channel dedicated DVR system. The problem is resolution.

The new cameras are Sony 420 line 1/3" cameras with IR. So they are a shade step up from the old. However, most reasonably priced 8 channel DVR's record at CIF resolution (352x288) The advantage seems to be you can record CIF at 25fps while if you want to go to D1 (DVD-ish quality - 720x576) you get a severe drop in frame rate (12.5fps or below) I'm presuming this is a limit in processing.

What is a better idea, CIF resolution at 25fps or higher quality at a much lower frame rate. To put some put some perspective, I need a reasonable frame rate on one camera as its on to a car park (Fast movement, cars etc)

Also bearing in mind I have night ops under IR floods. Is CIF enough?

Any pointers and many thanks!

FusionNet

hiya,

Ok its a little diffult to comment properly without knowing the site but Ill give you a few of my own opinions. So you asked a few questions. Ill answer in brief and you can come back and bounce ideas.

Resolution:

You can now buy DVRs that do D1 in real time 25fps. The problem is they are a little more expensive. A lot of DVRs have the option where you can split the resolution into blocks. So for example on ch 1-4 you have CIF, ch 5-8 CIF2 and 9-12 in D1. Best of all worlds.

Frame rate Vs Resolution

Oh this is a hottly debated topic on CCTV forums. I personally like as high frame rate as possible as lets be honest even though the law says 1fps is ok I think its rubbish. I like to set my DVRs to at least 12.5fps and the highest resultion I can depending on HDD size, compression used and quality needed.

With regarding your last point can you go into more detail. If you have IR flood lighting why then do you have IR cameras. Id be much more inclined to use a high quality box camera to work with the flood lighting.

Again all this depends on budget, you might have to sacrifice some spec for the budget. Let me know if you have any more questions or would like me to highlight anything else.

ironclaw

Hi Fusion,

Thanks for your reply. I'll try expand as best I can.

FusionNet wrote: »

Resolution:

You can now buy DVRs that do D1 in real time 25fps. The problem is they are a little more expensive. A lot of DVRs have the option where you can split the resolution into blocks. So for example on ch 1-4 you have CIF, ch 5-8 CIF2 and 9-12 in D1. Best of all worlds.

I found that out recently. 12.5fps is perfect for my needs and to be honest I've never needed higher than 10fps. The minimum I work at is 4fps in a courtyard area.

Frame rate Vs Resolution

Oh this is a hottly debated topic on CCTV forums. I personally like as high frame rate as possible as lets be honest even though the law says 1fps is ok I think its rubbish. I like to set my DVRs to at least 12.5fps and the highest resultion I can depending on HDD size, compression used and quality needed.

The IR cameras are in zones with practically zero ambient light (except moon light etc) So they do need IR floods. They are IR cameras aswell as the budget allowed for that at the time.

The main question is, at CIF at 25fps, will the resolution be good enough from a 420 line camera to make out a face etc? I know the distance in IR is minimal but at say 5m, just above someones head in pitch darkness, could you see a face clearly?

With regarding your last point can you go into more detail. If you have IR flood lighting why then do you have IR cameras. Id be much more inclined to use a high quality box camera to work with the flood lighting.

That was a chicken and egg mistake on my behalf and also a budget one. There were IR Cameras that were then upgraded with floods put in nearby.


Thanks for all the help but I suppose my main question can be summarised as: CIF at 25fps with a 420 line camera - Can it make a face out at night?

FusionNet

Hi again,

ok to answer this one "CIF at 25fps with a 420 line camera - Can it make a face out at night"

Firstly Id recommend CIF2 and your you have better quality yet you can still have a high frame rate. Secondly with regarding the hardware, 420tvl is not that high and there can be a huge difference in two identical cameras due to the electronics inside. Finally IR makes getting a facial shot very difficult especially if its close. This is due to IR reflection from skin. What you'll find is if someone is close or the IR is very focused you'll get wash out and basically the face can become one big white blob!!!

I presume your stuck with the kit you have ya? Is facial ID very important on this site?

ironclaw

FusionNet wrote: »

Hi again,

ok to answer this one "CIF at 25fps with a 420 line camera - Can it make a face out at night"

Firstly Id recommend CIF2 and your you have better quality yet you can still have a high frame rate. Secondly with regarding the hardware, 420tvl is not that high and there can be a huge difference in two identical cameras due to the electronics inside. Finally IR makes getting a facial shot very difficult especially if its close. This is due to IR reflection from skin. What you'll find is if someone is close or the IR is very focused you'll get wash out and basically the face can become one big white blob!!!

I presume your stuck with the kit you have ya? Is facial ID very important on this site?

Thanks for all the help.

I am stuck with the kit to an extent as there are budget constraints. I'd love to put in 540 line cameras and D1 recorders etc but I don't have the cash :pac:

I appreciate the wash out remark, I've noticed that but there isn't much one can do I presume?

CIF2 is a option if I can get a DVR to match. Again, budget!

Facial ID is important as there isn't much point if there is any trouble and we can't ID a face especially at night when colors become shades of grey