I'm confused. Just bought a JVC GY HD 250. Should I purchase the FS4 or the HD100? I've been reading about the FS4 40GB upgrades. But, when I go to the Focus Enhancements web site it says that the FS4 is not compatible with the JVC 250.
What are the differences between the FS4 and the HD100?

I use the HD100 with my JVC GY-HD110 camera. I don't personally own the FS4 but from what I understand the two devices are almost identical. The FS4 will work with your camera just like it will work with any other. The HD100 though will support some of your camera's more advanced features, such as all of your camera's frame rates- it also just communicates better with the JVC pro HD camera, with time code settings, a hard drive record icon in the viewfinder, when you turn your camera off the HD100 will shut down as well. Additionally the HD100 can be set specifically to recieve commands from your camera, allowing for completely tapless recording and more control through the camera then what you would get with simple syncro control that you'd get with the FS4.

Bottom line- the FS4 will work for you, but you will be limited in which of your camera's features and frame rates you can use with it.

Here's a e-mail I got from Focus when I asked the same question.

the way I read it is it will do 24p as well as 30p but NOT in quicktime only native which is fine for me I dont use FCP and if I did I dont mind converting it. I think you can go totally tapless too.

Dear Randy,

Thank you for your interest in Focus Enhancements. After conversing with our
technical support group and product manager we feel that your requirements for
recording will work with an FS-4 Pro HD model(must be a 60, 80, or 100 GB). You
can control the FS-4 Pro HD unit from the camera, but it will not have all
unique control modes. You can record in Quick Time 720/30p, but not in 24,25,50
or 60. It will do the 10 second loop through. You can also record onto tape and
the unit at the same time as well.

Yet we still highly suggest purchasing the DRHD100 for any JVC camera because we
do not specifically test the FS-4 series with JVC cameras because that is not
our market. There are some features the FS-4 will not do with the JVC cameras
and they are mentioned below. I have provided information on were to purchase
below. If you have decided to purchase the DR-HD100 DTE Recorder then please
contact JVC for purchase information at www.jvc.com/pro or dial 714-527-7500.

Features of DR-HD100 compared to FS-4 HD
1.) DR-HD100 has additional record modes. Series Record and Split Slave modes
(special with the GY-HD100/101 cameras) - FS-4 HD does not.

--Series Record = automatically starts recording to disk when a tape is close to
the end of the record session.
--Split Slave = the GY-HD100/101 camcorder controls the DR-HD100 separately from
the camcorder's tape transport. The DR-HD100 is slaved to the camcorder's REC
TRIGGER button, located on the GY-HD100/101's left panel.

2.) DR-HD100 has more IEEE 1394 status communications with the GY-HD100/101
cameras to show additional status info on the Camera view finder.

3) The DR-HD100 can record QuickTime in 720/24/25 and 30p. While the FS-4ProHD
can only record QuickTime in 1080/50/60i and 720/30p.

Featuring a comprehensive backlit display, an easy-to-use menu system, a hard
drive, and a removable, rechargeable battery, the Focus FS-4 is the perfect DTE
companion for DV and HDV handheld shoots. Designed for use in even the roughest
conditions, the FS-4 includes a six- or ten-second (model-dependent) electronic shock
cache to ensure that you never lose footage. Audio, video, timecode, and control
information is passed through a single FireWire cable, allowing you to record to
disk and tape simultaneously. And when recording is complete, your footage is
ready to edit instantly—no capturing, file transfer, or file conversion is
required. FS-4 Portable DTE Recorders are compatible with a wide range of
nonlinear editing systems.

Attached you will find a description of our FS-4 Family; as well as, the user
manual to help answer any minor tech inquiries. You can purchase the DTE
recorder(s) from any of the following Distributors below. Additional
reseller/distributors can be found on our website at www.focusinfo.com. Please
feel free to contact me with any further inquiries. Thanks.