Wednesday, October 31, 2007

Camera Resolution Selection

Remember this general rule of thumb when selecting a "HIGH RESOLUTION" camera: If a camera manufacturer states "xxx by xxx pixels" as a "resolution", then put that camera down and run. Quality cameras don't play this game. They state real horizontal resolutions. If the Horizontal Resolution isn't either 420,480, or 540, steer clear. Lower quality and older CCD chips state resolutions in pixel dimensions. High quality CCD chip makers will either carry 480 or 540..anything less..or an odd number near this resolution would come from a lower end product.

Once upon a time, a camera manufacturer handed me their latest camera and said it was the highest resolution IP camera they had available. When I asked about resolution, they started giving me active pixel dimensions. It wasn't until I ran the camera through a waveform analyzer that they finally said, "you are keen to this" when told that 376 lines of resolution did not qualify as "high" in my book. Never have I seen a high quality camera that gives resolution specs solely in pixels.

5 comments:

solinym said...

Hey, this is kind of interesting. I'm a security researcher who had an interest in building his own computer-integrated home security system and wasn't easily able to get the technical information I needed. I've had a difficult time getting any information even from books. Just recently a friend showed me how CMOS cameras have so much more noise than CCD cameras.

You seem to be suggesting that the actual resolutions vary from the resolution made available to the end user. Are you saying that they resample (using interpolation) to a higher resolution, or something else?

I'd like to include some information on physical security systems in my security concepts paper, eventually.

You can find it here:
http://www.subspacefield.org/security/security_concepts.html

Security.Insider said...

Sorry for the delay. Actually, what I've found is that the lower end manufacturers tend to use lower resolution (say 8bit instead of 12bit) digital to analog converters that result in a much more "jagged" waveform. This ultimately results in a lower resolution score, when measured with a waveform analyzer against an analog TVL chart. Some of these manufacturers will go ahead and claim the "480" lines of resolution that the chip is capable of because either they know the end user will never have the gear to test it, or they simply don't know what they are doing, and just follow a reference design provided by the chip manufactuer, only using cheaper components that end up degrading their product. I have found some manufacturers of IP cameras that use interpolation to achieve 4CIF image size, using only 2CIF resolution information.

Hank Roberts said...

Can you identify specific camera models for us?

Hank Roberts said...

Can you tell us any specific camera models that you know have good resolution, from your tests?

I want a pair of cameras to do small stereo movies, USB or firewire.

Security.Insider said...

Ya, there are a couple of really good manufacturers out there. Pelco and Bosche are by far the industry leaders. They make most of their own chipsets, and don't simply follow the reference designs.