My dumb questions thread

[Dirk_D 0]

What's with the blue in the blacks? This image is from a DS-2CD2032-I

 

[buellwinkle 0]

The reflection of the sky or pool on the shiny surfaces?

[MaxIcon 0]

That's from the lens, and is called chromatic aberration, or color fringing. This is common on inexpensive optics, and most low- to mid-range cams have it. It's usually worse with bright light, and often shows at brightly lit high-contrast edges.

http://en.wikipedia.org/wiki/Chromatic_aberration

 

It's caused by different wavelengths having different focal lengths, which is the same thing that causes IR to focus at a different point than white light, requiring IR correction on day/night lenses.

 

Better lenses have less of it, but a good compensated lens can cost more than the entire cam in the case of the Hik 2032.

[catseyenu 0]

That's from the lens, and is called chromatic aberration, or color fringing. This is common on inexpensive optics, and most low- to mid-range cams have it. It's usually worse with bright light, and often shows at brightly lit high-contrast edges.

http://en.wikipedia.org/wiki/Chromatic_aberration

 

It's caused by different wavelengths having different focal lengths, which is the same thing that causes IR to focus at a different point than white light, requiring IR correction on day/night lenses.

 

Better lenses have less of it, but a good compensated lens can cost more than the entire cam in the case of the Hik 2032.

 

Any recommended camera settings to help lower the effect?

[dexterash 0]

Since it has to do with the hardware, you can't do much. You can check some different AWB/exposure settings that might lower that effect, but there isn't any magic solution and you might get to other problems.

 

Your best bet is to change/try different(as in better) lens.

[buellwinkle 0]

Ahh, the purple fringing. I though he was talking about the blue reflections from the pool. That's caused by very strong contrast. If you can reduce the contrast, paint everything black or paint the bbq white you may be able to reduce the contrast enough to eliminate it. Also, set your contrast down a bit on the camera, you are way overexposed on the concrete. Turn off BLC if you have that turned on as that will overexpose bright areas.

 

Even on $1,000 lenses on my DSLR I get some degree of purple fringing in very high contrast situations but Nikon has fixed the problem in the camera firmware. Not sure CCTV companies are that sophisticated yet or even care about it. Even on Mobotix domes that cost about $1,500+ have the same issue.

[catseyenu 0]

Thank you gentlemen, I appreciate the tips and discussion.

[Dirk_D 0]

That's from the lens, and is called chromatic aberration, or color fringing. This is common on inexpensive optics, and most low- to mid-range cams have it. It's usually worse with bright light, and often shows at brightly lit high-contrast edges.

http://en.wikipedia.org/wiki/Chromatic_aberration

 

It's caused by different wavelengths having different focal lengths, which is the same thing that causes IR to focus at a different point than white light, requiring IR correction on day/night lenses.

 

Better lenses have less of it, but a good compensated lens can cost more than the entire cam in the case of the Hik 2032.

 

You know, I kept trying to look up abberation, I thought I even tried spelling it like aberration. Thanks for the explanation.

[Dirk_D 0]

Ahh, the purple fringing. I though he was talking about the blue reflections from the pool. That's caused by very strong contrast. If you can reduce the contrast, paint everything black or paint the bbq white you may be able to reduce the contrast enough to eliminate it. Also, set your contrast down a bit on the camera, you are way overexposed on the concrete. Turn off BLC if you have that turned on as that will overexpose bright areas.

 

Even on $1,000 lenses on my DSLR I get some degree of purple fringing in very high contrast situations but Nikon has fixed the problem in the camera firmware. Not sure CCTV companies are that sophisticated yet or even care about it. Even on Mobotix domes that cost about $1,500+ have the same issue.

 

BLC is off, I'll play with the contrast tomorrow. I've adjusted the WDR settings and played with shutter speed (a few things).

 

I should post an un-cropped picture, there's a stairwell that's difficult to see most of the time, and at night, I want to play with some external IR.

 

Sounds like I need to go through my digital photography book again & try to absorb some more. (I've read a lot of CCTV books too, I guess if anyone has professional recommendations I'd love to hear them too.

 

 

>>>>edit: Please excuse the mess - this is about 8:45pm, sunset is at 8:59pm