1000TVL Cameras?

[steve4323 0]

Hi Guys and Gals,

 

I haven't been in the CCTV game all that long, but all the people I have spoken with inc suppliers have told me you cannot get higher than a 700TVL camera for an analogue system. Yesterday I was browsing the web and found a supplier that does 1000TVL cams.

 

Can anyone tell me if these are real or false marketing in some way? Or does anyone use them, is the resolution that much better?

 

Cheers,

Steve

[Don Stephens 0]

I'm guilty of telling people that there isn't anything above 700TVL with standard def analog cameras.

 

The reason is, I simply don't view the cheap 800TVL and 1000TVL image sensors to be high enough quality to really recommend. You can find some that are programmed very well, but even those are only the equivalent of a decent 700TVL camera.

[survtech 0]

The point is, analog is analog, warts and limitations and all. Analog has a TVL limitation of approximately 600TVL. Yes, you can run 960H cameras as if they were true analog cameras but the resolution differences between 500TVL, 550TVL, 600TVL, 700TVL, 960H, etc. are really miniscule.

 

So how do manufacturers get away with their claims? Two words: They cheat!

 

Let's start with "700TVL" cameras. By definition, TV lines are supposed to be measured in a square section of the actual image, where the width is equal to the total height of the screen. It doesn't matter if the screen is 4:3 or 16:9, the area to measure TVL is only the horizontal part of the picture that is the same measurement as the screen height. So a "700TVL" camera is actually a 525TVL camera. Confused?

 

 

Let's say you test a camera on a 4:3 monitor using proper methodology and it measures 500TVL. This is where the manufacturers' cheating comes in play. Over the entire width of the screen, you would actually be able to see 500/3*4 lines or 666 lines. That is not actual TVL, but many manufacturers don't care and will publish that as their resolution spec. The same applies to the 800TVL spec. Actual TVL on such a camera would be 600TVL but with their "creative math", many manufacturers would take the 600TVL actually measured and divide it by 3 and multiply that by 4 to come up with 800TVL.

 

The effect is even more exaggerated by 16:9 monitors. The same actual 500TVL camera (500/9*16) translates to 888 lines. So a 1000TVL camera is actually 562.5TVL.

 

[steve4323 0]

Thanks for the info guys. I guess I will stick to the 700TVL and HD.

 

On the back of the original question - I currently use DigitalDirectSecurity as a supplier and always order from their SonyEffio or Lucem range (Not that fussed on their Sharp range). Has anyone had any better images from other camera manufacturers?

 

Thanks for the help,

Ste

[SunnyKim 2]

The video data from analog camera is transmitted via TV signal (NTSC, or PAL), which is quite band limited. Whatever number of TVL, High Details should be low pass filtered to be squeezed in such a low bandwidth. To me, above 650 TVL is more than enough.

[yl_fang 0]

right， that high TVL is kind of cheating, but few and few understand tht, so don't care too much on that parameter, just focus on the pix