Kell Factor and effects on UK CCTV Operational Requirements

[glynnseal 0]

Hi all,

 

My first post here, so please be gentle

 

I am working on a schedule that calculates meeting the Operation Requirements goverened by the UK CCTV Standards (namely NSi CoP, BS and HOSDB Ops Manual 2k9).

 

As the NSi and BS standards seem to float round the PAL video standard for their determination of how much of the screen a 1.6m target should occupy this is fine. The complications come when using cameras that use source resolutions different to the PAL standard, for example 720p and 1080p (HD cameras).

 

The HOSDB Ops manual 2009 makes very specific mention of this. A 720p camera doesn't need the full 100% of the screen height to achieve the same Operational Requirement. I understand this.

 

The HOSDB manual makes a caveat mention of the Kell Factor (I'll refer to this as KF from now on) to state that the perceived vertical resolution of a 576TVL PAL signal is actually 400TVL. I can use this figure of 400 to base my scaling of the OR's, the same way as the HOSDB manual shows.

 

1) The issue I am not clear on is that if the KF also affects the horizontal resolution in the same way, and by the same amount. The HOSDB manual suggests that it doesn't.

2) If I use an LCD monitor to display the same PAL source image, do I still use the KF0.7 value? Is the monitor introducing the Kell Factor issue, or is it down to the video transmission standard?

3) The confusion comes when I think about the PAL camera and its two possible aspect ratios of 720/400TVL and the 720/576TVL. What is the OR scale factor and its impact for both Vertical and Horizontal Angles of View when going from PAL to say 720p? Which PAL resolution/aspect ratio do you use to scale for both H and V angles of view?

 

Hope this makes some sense to someone, because its melting my little brain

 

Thanks,

glynnseal

[tomcctv 190]

Hi all,

 

My first post here, so please be gentle

 

I am working on a schedule that calculates meeting the Operation Requirements goverened by the UK CCTV Standards (namely NSi CoP, BS and HOSDB Ops Manual 2k9).

 

As the NSi and BS standards seem to float round the PAL video standard for their determination of how much of the screen a 1.6m target should occupy this is fine. The complications come when using cameras that use source resolutions different to the PAL standard, for example 720p and 1080p (HD cameras).

 

The HOSDB Ops manual 2009 makes very specific mention of this. A 720p camera doesn't need the full 100% of the screen height to achieve the same Operational Requirement. I understand this.

 

The HOSDB manual makes a caveat mention of the Kell Factor (I'll refer to this as KF from now on) to state that the perceived vertical resolution of a 576TVL PAL signal is actually 400TVL. I can use this figure of 400 to base my scaling of the OR's, the same way as the HOSDB manual shows.

 

1) The issue I am not clear on is that if the KF also affects the horizontal resolution in the same way, and by the same amount. The HOSDB manual suggests that it doesn't.

2) If I use an LCD monitor to display the same PAL source image, do I still use the KF0.7 value? Is the monitor introducing the Kell Factor issue, or is it down to the video transmission standard?

3) The confusion comes when I think about the PAL camera and its two possible aspect ratios of 720/400TVL and the 720/576TVL. What is the OR scale factor and its impact for both Vertical and Horizontal Angles of View when going from PAL to say 720p? Which PAL resolution/aspect ratio do you use to scale for both H and V angles of view?

 

Hope this makes some sense to someone, because its melting my little brain

 

Thanks,

glynnseal

 

 

hi the first problem is the amount of governing bodys ...... that took part in the cctv standards. 2009 they all added there little bit and it just confusses everyone. 2010 / 11 a new white paper has be draw to solve the problems. and when all bodys are happy then new standards will be out mid end 2012.

 

give me a few days and i will email you the white paper that give changes. HOSDB is good reading along side DPA

 

can i ask why you are looking into this ???