Cctv Zoom Lenses And Other Options

[jelly belly]

Hi Tubularowl

My Graphic CCTV Lens Software will give a you a good idea of the image size you are likely to get from any given lens size. You can download and use for 30 Days Free of charge.

http://www.software4cctv.co.uk

Jelly Belly

[Rich]

Hi Tubularowl,

That camera you mentioned above with that lens (is that a zoom lens?) How does it all work? I am clueless about the lens. For a day/night is that a good choice? What is the range of that lens? Are you able to control than lens with your DVR?

Sorry for the dumb questions.

,

Mike

The lens is vari focal, meaning that you can manually set it up between its focal points. Basically it means that you can adjust the lens between the ranges it allows rather than having to buy a different lens for different views. A zoom lens is different and you add a power source to it via a controller of some sorts and that allown you to move the lens remotely, as used in pan and tilt cameras and domes.

[tubularowl]

Hi Tubularowl

My Graphic CCTV Lens Software will give a you a good idea of the image size you are likely to get from any given lens size. You can download and use for 30 Days Free of charge.

http://www.software4cctv.co.uk

Jelly Belly

Thanks for that,

The camera and lens look like a good bet. I just need to chose an IR lamp source now. I've seen them advertised at up to 70m distance on flood but how true is that?

My current 20m IR camara is only good for about 15ft in darkness (less than street lamp brightness)

The lens is vari focal, meaning that you can manually set it up between its focal points. Basically it means that you can adjust the lens between the ranges it allows rather than having to buy a different lens for different views. A zoom lens is different and you add a power source to it via a controller of some sorts and that allown you to move the lens remotely, as used in pan and tilt cameras and domes.

The lens I'm looking at is a zoom lens. Do you think I would be better with a varifocal one. I've not seen a lens on this site that has the visual range (50mm) in a varifocal form

Ray

[Rich]

Thanks for that,

The camera and lens look like a good bet. I just need to chose an IR lamp source now. I've seen them advertised at up to 70m distance on flood but how true is that?

My current 20m IR camara is only good for about 15ft in darkness (less than street lamp brightness)

The lens I'm looking at is a zoom lens. Do you think I would be better with a varifocal one. I've not seen a lens on this site that has the visual range (50mm) in a varifocal form

Ray

Hi ray,

Are you looking at this lens http://www.rfconcepts.co.uk/6-60%20lens.JPG

That is a vari focal direct drive auto iris lens. The lead that is attached is there to power the motor of the lens iris, which is done by the camera, it does not control the focal point.

[tubularowl]

Hi ray,

Are you looking at this lens http://www.rfconcepts.co.uk/6-60%20lens.JPG

That is a vari focal direct drive auto iris lens. The lead that is attached is there to power the motor of the lens iris, which is done by the camera, it does not control the focal point.

So thats not really what I want is it? I want a varifocal lens that can be manually set?

The link you sent is similar to the one I've been looking at (5-50mm)

[Rich]

http://www.vista-cctv.com/lense_zoom.htm <These are what typical zoom lenses look like.

http://www.2seetv.co.uk/acatalog/Cameras___Advanced.html <These are cameras with zoom lenses.

http://www.vista-cctv.com/lense_vari.htm <These are varifocal lenses

http://www.wedgwood-group.com/panasonic_45...o_iris_lens.htm <This is a fixed auto iris lens

http://www.rfconcepts.co.uk/6-60%20lens.JPG <This is an auto iris varifocal lens.

You are looking for either a Auto Iris, fixed focal lens of 40mm depending on your calculations.

Or if you are unsure of what lens you will actually need, or think that you may want to get a wider image at some time then a vari focal, auto iris lens would be the obvious choice.

Auto Iris means that the iris of the lens opens and closes depending on how much light is passing through the lens, the camera (or lens) can then adjust the iris to stop too much or too little light getting to the ccd chip. Generally these are used where the light changes, i.e. outside.

You need to make sure whatever lens you get works with the day/night camera.

A zoom lens to us usually means one that can be controlled remotely, a manual zoom lens is set manually at the camera and cant be changed unless you physically alter it at the camera which is what we refer to as varifocal.

[Doktor Jon]

Just to cause even more confusion

Whilst a manual zoom lens and a Varifocal appear to do much the same thing, it's a bit like saying petrol and diesel engines are identical.

Zoom lenses are generally more complex in the way the bits of glass (elements) are moved in relation to each other to achieve a change in focal length. As such, they are generally far better corrected, and usually provide a much better overall optical performance.

A Varifocal, tends to be a more simplistic optical design (where 'groups' of elements are moved in relation to each other), and as such are not in general terms as high performance as an equivalent zoom.

An obvious example might be something like an 8 - 48mm manual zoom lens, which would be significantly more expensive than say a 5 -50mm Varifocal. Apart from a slight difference in coverage, they could mistakenly be regarded as doing much the same thing, when in practice there is a noticeable difference.

Bottom line of course is, you pays yer money .....

[Rich]

Just to cause even more confusion

You do seem to make a habbit of it

Why haven't you applied for trade status, I'm sure your knowledge would be a great help in the CCTV forum.

[Doktor Jon]

You really don't want to know about my habits

Trade status .... umm, never really thought of that!

Considering I was "in the trade" long before Norbain was born, actually trade supplying come to think of it, and installing, and servicing, and technical support, and....and .... how depressing!

You guys seem to manage fine without me boring the wotsits off yer, but then I can't promise I won't do that occasionally if the need takes me.