Night lic plate capture. Will 1/2" CCD w/IR correction do it

[sequoia 0]

I've standardized on Bosch cameras, as the WDR cameras have worked pretty well for me. What does not work well right now is an older, non-bosch, non-WDR cam with 50mm lens for license plate capture. It is blurry/fuzzy and washed out at night. It's not a day/night cam but illumination in the general area is pretty is good. (A car wash well lit at night.)

 

I want to install a Bosch WDR day/night cam as a replacement for my older license plate cam, maybe a LTC0498 1/3" CCD with varifocal lens. But, for more money, I could get a Bosch LTC 0630 w/IR correction lens. The LTC 0630 has a 1/2" CCD, and the IR correction lens sounds good.

 

Without the benefit of practical experience between the two, how much improvement should I expect with a 1/2" CCD compared to a 1/3" CCD when it comes to picture quality, and how much benefit would I get from night time images with a IR corrected lens compared to a standard varifocal lens. Would this only make a difference if I add an IR illuminator as well?

 

I need close to the 50mm adjustment for enough zoom to read the license plates on the moving vehicles.

[rory 0]

1/2" wont be better quality, but it normally can see more in low light and be more sensitive to Infrared light - depending on the camera and lens ofcourse.

 

If you are using single low light camera for a Day Night application, then you should get a Day Night lens. In the past they were not available but you can get them everywhere now. Day Night lens reduces the focus shift commonly experienced with a day night, low light color, or BW camera using a varifocal lens. With a non Day Night lens you must focus it for both situations, or 3 situations if you are also using Infrared, it normally would need to be focused off a little to compensate for the focus shift and this way it wont be 100% all the time. Day Night IR corrected lenses will also help with focus shift under IR light.

 

Also the 5-50mm lenses tend to be higher F-stops so generally wont see as good in low light, compared to a lens with a lower F-stop - depending on the 1/2" lens you use that might help.

[Soundy 1]

All an "IR corrected" lens does is eliminate the need to refocus between day and night modes.

 

IR focuses shorter than visible light, so if you focus a camera in "day" mode, when it switches to night mode and the IR cut filter flips out of the way, the IR light it captures will be focused slightly in front of the sensor, and the IR-produced images will be fuzzy.

 

An IR-corrected lens (which I'm guessing, "day/night lens" is just another term for) is designed to correct for this quirk of physics.

 

What's more likely causing your camera to go fuzzy at night is the loss of depth-of-field caused by the iris opening up under low light. In bright light, with the iris closed down, you'll be getting more DOF - so, for example, you may focus the camera at 50' but everything between 25' and 60' is also in focus; when it gets dark, though, and the iris opens up, your area of focus may shrink to only points between 45' and 55'. Something at 35', for example, would then be in focus during the day, but go soft at night.