Picked up this lens on a JVC-GY-DV500. I think lens is worth more the the DV500. Plan to use on my GY-DV5000 though.

Have a novice question, what is the extender used for and how would you use it?

Thanks for you reply.

Not familiar with this specific lens, but a built-in extender is typical of a broadcast-style lens.

It is a built-in telephoto adapter, typically adding 2x effective focal length. That is, when you switch it in, your lens becomes more telephoto, and would lose a couple stops of light as well.

You can flip the lever any time you have gone to the end of the zoom range of the lens, and think you want a bit more! Great for outdoor sports, etc., but getting that much telephoto may make you wish you are on a tripod.