# what does lens 4mm-9mm



## ebola

I have a camera and it has an adjustable lens 4mm to 9mm what is the distance to the object i can zoom to and still have good resolution.


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## DonaldG

4 - 9 mm lenses are usually associated with surveillance cameras (CCTV). What is the make & model of the camera?


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## ebola

its a 1/3" sond dsp color day/night camera, it is a surveillance camera has led's on it that turn on in low light or no light conditions. Its made by a company called cinturon, its model #7600sh. www.cctvimports.com is where i got it from,just type in 7600 in the search bar and it comes right up. im having trouble focusing on objects that are 10' away and was wondering if this was b/c of the small focal lenght, if I went to say a 35mm lens would i be able to get in close to objects 10-15' away better?


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## DonaldG

Hi Ebola
4-9mm is a very short focal length as you point out. Being short it will have a very large depth of focus. 

Once set to the hyperfocal distance, I would imagine it to be acceptably sharp from a couple of feet to infinity.

The camera has 500 lines + so should (read 'should') give reasonable quality.

I am not familiar with CCTV much and wonder what focusing method is. Is it a set focus by adjusting the lens manually? Or is the focus set at the factory and not adjustable. If that is the case, the factory will have set it to the hyperfocal distance. That is the optimum distance that give maximum depth of focus. In my estimation it should focus at the 10' distance.

By replacing the lens with a 35mm, you will be fitting the equivalent to a telephoto lens (the sensor is very small). You certainly would get in 'closer' to a subject 10 - 15' away. However, the 35mm lens will have a much shorter depth of focus.

Low cost cameras will, by definition, have a low cost lens. even if you were to replace the 4-9mm lens with a high quality lens, the sensor may not be able to reproduce the image quality.

If the camera is new and you cannot get good definition at 10 feet I would return it to the place of purchase and have it checked out.

EDIT: I have just re read the specs and note that the focusing is user presetable with a special tool. Try at 9mm focused at 10 feet. That should be about right. If it is still poor quality - then return it as suggested above.


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## ebola

thank for the info much appreciated.


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