help needed(please read)

[sodagar 0]

Hello everyone,

 

I have few questions pelase if any one can help.

 

1) If i use a high resolution camera 480 tvl ,1/3" ccd with 4mm lense,what will be the maximum distance for face recognisation?

 

2) What will be the diffrence between a 21" sony televsion and a 21"600tvl cctv monitor for use with above mentioned camera.(regarding details and calrity of picture)

 

3) Which compression fromat is the best regrading picture quality and saving space either the wavelet ,mpeg4 ,h.264 or anyother.

 

4) As far as the remote viewing is concerned what should be the specification of DSL line for getting maximum speed on remote viewing.(how many FPS?).

 

Thanks.

[Cooperman 0]

Hi sodagar,

 

Although you've posted some fairly straightforward questions, unfortunately there aren't really straightforward answers.

 

As regards using a high res. colour camera with a 4mm lens, to some degree the results will depend on the build quality of the camera, the lighting, the quality of the lens, and of course your transmission system.

 

If you have a top quality camera fitted with a superb optic under ideal lighting conditions, the image of a persons face displayed on a half decent monitor might just about be acceptable for recognition at 12 - 18 feet from the camera. Ideally you'd be looking for a face to occupy perhaps 1/6th of the screen height, in which case your target would need to be around 6' from the camera.

 

If at all possible, try and use a narrower lens (maybe an 8mm or longer, preferably 1/2" format or larger) at a greater distance, which should give you a much better quality image.

 

The comparison of a 21" TV and a 21" monitor will vary from one model to another. Depending on how mission critical your application is, and how much of a hammering you intend the display unit to receive. it's quite possible that the TV will fit the bill, although it must be stressed that it is not designed to work at the same level as an industrial monitor.

 

The issue of compression is another less than simple topic. In simplistic terms, MPEG 4 / H264 will produce smaller image files so will allow more images on a given disc space, but other formats such as MPEG 2 and Wavelet will produce less compressed images, and will therefore require more space for the same record period.

 

In practice, the settings on an individual DVR will significantly affect the efficiency and quality of the eventual recorded images.

 

As regards the DSL calculation, whilst our systems are significantly different from what's available in your neck of the woods, you'd best calculate your requirements, provided you know what the average image file size is, in relation to the number of cameras connected and the number of images per second.

Hopefully other guys will perhaps be able to give you some more specific figures, based on example standard equipment and systems available where you are.

[SUPERDAVE 0]

IN REGARDS TO THE DIFFERENCE BETWEEN TV AND CCTV MONITORS. MOST MANUFACTURERS CLAIM THAT THE NORMAL LIFE FOR A TV IS 5,000 VIEWABLE HOURS WHILE A PROFESSIONAL CCTV MONITOR IS 50,000 HOURS. UNFORTUNATELY MOST MANUFACTURER WARRANTY'S EXPIRE LONG BEFORE 50,000 HOURS PASS, SO THIS IS REALLY YET TO BE PRACTICALLY PROVEN. HOWEVER THE ISSUE OF BURN IN (WHERE THE MONITOR ACTUALLY SHOWS CERTAIN PARTS OF A PICTURE THAT DO NOT CHANGE EVEN AFTER ITS OFF) OCCURS A LOT FASTER ON A REGULAR TV. ALSO MOST CCTV MONITORS ARE LEFT ON CONSTANTLY AND THAT IS WHERE THESE DIFFERENCES WILL BE OBVIOUS.

 

ASIDE FROM THE RESOLUTION ISSUE IF THE MONITOR WILL BE SHUT OFF EVERY NIGHT THEY CAN GET AWAY WITH A TV.

[sodagar 0]

Thank you Cooperman for replying each question.

Regarding quest 2 i was looking for diffrence between picture qaulity of a cctv monitor and TV.

If a good performing camera of 480 resolution, 0.1 lux minimum illumination and S/n ratio of more then 48 db at AGC off placed indoor in excelent light conditions,how it will perform on a 21 inch sony vega as compared to cctv monitor of 600 tvl and if the same camera installed outdoors with poor light conditions at night ,which of the two will give better results .

[Cooperman 0]

The bottom line sodagar is probably about money rather than technical performance.

 

If you used a very expensive brand new CCTV monitor built perhaps 10 years ago and compared the overall picture quality to a much cheaper modern quality branded television, I wouldn't mind betting the modern TV would probably look better overall.

 

That said, a number of 'industrial' monitors are built using common components that are also used in some domestic televisions.

 

If you are looking to save on cost, and you've seen or know of a very good television with excellent picture quality, then it may well do what you want.

I should perhaps mention that some TV's and indeed some monitors can be less suitable for playing back recordings (particularly analog or time lapse), but nowadays this shouldn't really be a major concern.