just got my first job in CCTV/security at DIY shop but there

[halsaps 0]

just got my first job in CCTV/security at a DIY shop but there quality of images when you zoom in means they are useless how can I improve the quality we have dome and 4+ old style at the moment i don't know the makes. help v much appreciated.

[NotoriousBRK 0]

Well, you don't give us much to go on, but I'm going to guess that you've got low to mid grade analog cameras covering too much area.

 

Digital zoom expectations are mostly a factor of pixels per foot (assuming decent lighting, focus, etc.).

 

You'll want 50 pixels per foot minimum in most cases. This means an analog camera can cover an area about 14ft x 10ft max and give you good detail on zoom. Larger areas will yield less zoomable detail.

[Campbell 0]

just got my first job in CCTV/security at a DIY shop but there quality of images when you zoom in means they are useless how can I improve the quality we have dome and 4+ old style at the moment i don't know the makes. help v much appreciated.

 

Use megapixel cameras.

[Sawbones 0]

just got my first job in CCTV/security at a DIY shop but there quality of images when you zoom in means they are useless how can I improve the quality we have dome and 4+ old style at the moment i don't know the makes. help v much appreciated.

 

Use megapixel cameras.

 

This is the answer.

[troy6363 0]

Are megapixel cameras very expensive?

[Numb-nuts 1]

I get the feeling this whole project was dumped on you and to replace everything with IP cameras is going to be quite expensive. While IP megapixel cameras produce a great sharp image, so too can high resolution analogue cameras with the correct lens fitted.

 

What are the cameras you have already? Some cameras, even cheap ones have interchangeable lenses, some are fixed lens.

Choosing an appropriate lens will help achieve a correct depth-of-view and an appropriate image focussed correctly.

 

Imagine the view is flat on screen, from which point to which point do you want to view? If you just want to capture people's image as they pass through a doorway, the scene width would be the width of the door at a fixed distance. To now assign a distance from the camera, you need the horizontal distance to the doorway and then the height of the camera. Using the pythagorus law, you can calculate the actual distance to the door from the camera.

 

In reality, in your situation you can probably use a tape measure depending on the size of the DIY shop.

 

Now check the camera's spec sheet and find out it's lens size (mm) and it's CCD sensor size ¼", or ⅓" or ½" and the lens type if specified.

So now we have

The lens type, )could be C, CS or '12mm thread' board lens Thread as opposed to focal length.

the camera's lens size (mm)

a ⅓" sensor in the camera (Typically)

the scene width (in m or feet)

the distance from camera to the field of view (doorway) (in m or feet)

 

 

With this info, we can save some time using this online lens calculator

for an example, you have a camera situation thus;

 

⅓" sensor in the camera (assumed)

A horizontal distance of 15 ft to the doorway

a camera mounting height of 12 ft

Pythagorus:

225+144=369 , √369=19.2 ft actual distance to doorway

and the doorway is 4 ft wide (assumed)

 

putting all this data into the lens calculator wee see we need a 23.04 lens

 

in reality no such lens exists so we need to get one as close as possible to that figure

so changing the scene width to say 3.5 ft and calculating we see that the lens required changes to 26.33

and again no such lens exists but a 25mm lens is quite common so we can play a bit with the scene width to get as close to an available lens making sure we are still within an acceptable width.

 

 

 

I hope this is helpful

[Soundy 1]

Now check the camera's spec sheet and find out it's lens size (mm) and it's CCD sensor size ¼", or ⅓" or ½" and the lens type if specified.

So now we have

The lens type, )could be C, CS or '12mm thread' board lens Thread as opposed to focal length.

the camera's lens size (mm)

a ⅓" sensor in the camera (Typically)

the scene width (in m or feet)

the distance from camera to the field of view (doorway) (in m or feet)

 

 

With this info, we can save some time using this online lens calculator

for an example, you have a camera situation thus;

 

⅓" sensor in the camera (assumed)

A horizontal distance of 15 ft to the doorway

a camera mounting height of 12 ft

Pythagorus:

225+144=369 , √369=19.2 ft actual distance to doorway

and the doorway is 4 ft wide (assumed)

 

putting all this data into the lens calculator wee see we need a 23.04 lens

 

in reality no such lens exists so we need to get one as close as possible to that figure

so changing the scene width to say 3.5 ft and calculating we see that the lens required changes to 26.33

and again no such lens exists but a 25mm lens is quite common so we can play a bit with the scene width to get as close to an available lens making sure we are still within an acceptable width.

OR, save yourself a ton of math and just use a varifocal lens, and adjust it to get the view you need. Comiscar/Pentax have a 5-50mm C/CS-mount that lists for <$100.

 

Edit: BTW, that's a neat lens calculator... this one will also let you enter the camera height and do the angle calculation for you: http://cctvlenscalculator.com/

[Numb-nuts 1]

I didn't mention a varifocal lens which would be a great choice, but when I have recommended these to newbies in the past they have hit a load of difficulties with focusing, but certainly a varifocal lens with a suitable range would be a good choice.

Some cameras are supplied with a varifocal lens already installed. You may even have one or two in the equipment supplied to you.

[Bunited2 0]

What I don't understand, or wasn't presented in the original

post was: zoomed in what? he mentioned a dome, was it

already a varifocal, was it a digital zoom through a dvr, etc?

 

If he was able to zoom in something (with a lens, manual, or

motorized) there had to have been a separate focal capability,

nothing was mentioned in the post.

 

Something tells me there's a focal ring he doesn't know about,

or a screw pickup device adjustment?

 

Bunited2

[Numb-nuts 1]

It just occurred to me, if you are planning on doing more CCTV in the future, you should invest in a portable 3.5" screen so setting up lenses and focusing can be done at the camera as you adjust the lens. I've seen the cheapest simple versions of these on ebay for about £50 but not sure just how good these are but it;s sure to save yuo going up and down a ladder like a demented yo yo and walkie-talkies are not really a substitute because you need two people and it's not an ideal way to focus a camera.

 

What I should also have mentioned, with lenses the smaller the focal length value, the wider the angle of view and conversely the larger the focal length value, the narrower the angle of view (and the further away you can focus) but it's just a generalized statement. So a 2.5 mm lens has a wide horizontal angle and a 100 mm lens has a narrow horizontal angle of view (and can focus much further away).

 

addendum

I am fond of the calculator I have linked to as it visually reminds me what I'm trying to achieve.

I also quite like the other calculator, I like the fact it does the pythagorean calculation for you AND allows you to specify height or width. I have never yet needed to consider too carefully the scene height but can envisage one or two scenarios where this would be useful. So far I've managed without but then the jobs I undertake aren't usually that demanding

and the equipment and focal specs are already decided before I arrive on site. I just do the nuts and bolts so to speak.

Edited November 22, 2011 by Guest

[Numb-nuts 1]

What I don't understand, or wasn't presented in the original

post was: zoomed in what? he mentioned a dome, was it

already a varifocal, was it a digital zoom through a dvr, etc?

 

If he was able to zoom in something (with a lens, manual, or

motorized) there had to have been a separate focal capability,

nothing was mentioned in the post.

 

Something tells me there's a focal ring he doesn't know about,

or a screw pickup device adjustment?

 

Bunited2

 

This is exactly what I was talking about with newbies not understanding varifocal lenses. Well noticed.