Can't get uniform focus across the picture

[andriusst 0]

Hi everyone,

 

I'm building DIY CCTV system to record the car park where I keep my car.

 

I am having problem getting clear picture. I'm using focus handle on a lens to focus the picture but if I get middle of the picture in perfect focus then sides become blurred. I would be grateful if someone could point out what I am doing wrong. Am I missing some optics piece or got incompatible setup?

 

The setup is IQEye 702 camera, C-CS mount adapter and 1/2" 50mm fixed lens with manual iris and focus (cheap). Thanks in advance.

 

Andrius

[Horizon 0]

Hi andriusst.

Have a look on Google for "depth of field".

If you have the iris set wide open, the depth of field will be at a minimum. If the objects at either side of your picture are at different distances (large distances, possibly many meters) from the camera, they may be outside the depth of field, and be out of focus.

If you partially close the iris, the depth of field will increase, but you'll have poor low light performance.

The depth of field also depends on the lens design.

 

The lens itself could be faulty, or a poor performer. Angle the camera so the object in the center of the picture appears at either side, and see if the object remains in focus.

[vin2install 0]

You got the wrong lens for a sensor of that size. Try getting a better lens to match the size of the sensor.

[andriusst 0]

thank you both for taking time to reply. I believe I'm seeing is a combination of both. I won't be able to adjust iris any time soon as I haven't got the ladder and neighbours who do have it are away on holiday. But I am thinking that closing down the iris a bit will have a negative impact on night time picture. So auto iris would be good. Camera however does not have iris control circuit. Can I get a lens with auto iris that has a light sensor on it?