If you are using a whole mixture of equipment, chances are you have a mixture of BNC, phono and maybe even other connector types for your video interconnect. Which is best and why?…
Answer: The BNC connector with its rigid construction, correct impedance and mechanical locking ring is by far the best type of connector to use for all types of video interconnect. The problem of course is that a lot of prosumer gear uses the good old phono connectors, because they are much cheaper to make. This means that inevitably you will have to interchange between different connectors in your setup.
In this context the best type of connector to use is the one that gives the best quality of connection (both electrically and mechanically) while minimizing the amount of cables and connectors needed to make the link. There is no point in using lots of extra adapters and cables JUST to be able to use BNCs, if they don’t give you any benefit. If a cable is static for most of its life, or lives in the same place, or has no strain applied, or is only connected or disconnected infrequently (say, inside an equipment rack) then a phono connection may be fine. If, however you are attaching a long cable that may be pulled, or jarred, or that is disconnected and reconnected very often (e.g. on a camera or projector)then you should be looking to convert to BNC as quickly as possible.
This is one advantage of cabling up your equipment into a rack or box. It allows you to do all you connector adapting in a nice fixed, secure way, so no problems later. You can use short ‘jumps’ to go from one type to the other.