The Live Event Producer's Guide to the Sony NEX-FS100

Parfocal Lenses

We've covered a lot of ground with zoom lens options, but before you decide which lens mount you will build your kit around, one of the most important factors you should consider when purchasing a zoom lens is that it holds focus when you change focal length.

It might come as a surprise to many videographers that most SLR lens are varifocal, which means they don't hold focus when the focal length changes. A lens that does hold focus is called parfocal, but don't expext the focal nature of a lens to be listed in lens specifications. I can't think of a single lens that's advertised as parfocal. Each of the lens mounts described above have parfocal lens options, but you may not find one in every range.

Using the FS100 for Live Events

So which of these factors--autofocus, iris changes, image stabilization, EXIF data, fixed aperture, parfocal lenses, smooth zoom ring, and fast lenses--are the most important for online video producers shooting live events?

This is the topic of a great deal of debate, much of which tends to skew toward lenses the user already has, and opinions will vary depending on the type of work you are shooting. It also gets complicated really fast when you realize that some features become more or less important with other selections. Unfortunately, you can't currently have it all. Or can you?

Iris control is important, but lack of smooth iris changes can be offset by adding a variable ND filter. You lose a bit of light when you add this type of filter, although this isn't as important on a large-sensor video camera because adding a bit of gain is not as devastating as it is on small-sensor video cameras. And if Sony can solve the smooth iris change problem on the LA-EA2 adapter with the release of a firmware update, this might add another option for iris control in the favor of A-mount lenses.

A 2-camera dance recital filmed by Shawn Lam Video on the Sony NEX-FS100