ZoneMinder Forums

The resolution of an analog camera is often given as the number of TVL provided in the
analog signal. Examples of the resolution given in TVL are 380, 420, 480, 550 and higher.
Generally costs of cameras increase as TVL increases.

Hardware (e.g., DVR Card) is required to convert the analog signal into a digital format
usable by zoneminder. Often the hardware utilize the Conexant 878A chipset or Philips saa7134 chipset for converting the signal. These chipsets have their own limitation and
there are limitations inherent based on the analog nature of the signal itself.

Due to the limitations of the DVR cards (and analog signal),
zoneminder may or may not be able take advantage of cameras with higher TVL.
There may be a limit at which point increasing the TVL of a camera provides no
or little benefit to zoneminder.
If there is a maximum usable TVL, then there is no reason
to expend funds on cameras having higher TVL.

It was suggested to me that cameras having TVL higher than 380 offer no or minimal benefits over 380 TVL cameras when using DVR cards with zoneminder.

Is this true? When do marginal diminishing returns kick in in terms of TVL?

I wondered this as well.

I purchased one 450TVL camera ($62 on monoprice.com)... I get a pretty good image from it. I plan to purchase a 340TVL ($42) to see how much difference it really makes. If I get it figured out I'll post screenshots.

In my opinion, the "limit" relates to the max resolution supported by ZM, which as far as I know is 640x480 from a bt898 card. I think the card supports 720x480 or something... anyway, you have to weigh that against the quality of the digital image. I found this pdf that sheds light on the conversion:

http://www.securitysales.com/resources/SS3dumies.pdf

That does not really provide an answer as to which to buy.

I know my camera looks visibly worse when captured at 320x240, so I know 450TVL has better picture than 320x240 can support.

Strangely, the only images I have ever seen from that camera are digitized versions of the analog signal.

Yeah, I was wondering this too. I'm going to buy new analog cameras and have two cards, one with bttv and another with saa7134 chips.

I hope someone could provide more info on this topic.

Thanks