Sony FX5: Open Gate, IBIS and Anamorphic Desqueeze Limits

Sony’s FX5 is the first Sony body to combine open-gate recording, in-body stabilization (IBIS, or sensor-shift stabilization) and anamorphic desqueeze in one compact cinema camera. Anthony Gugliotta spent a week testing it against the Canon EOS C50 and found that the three features do not work together as a complete shooting package.

These three functions have become the most requested features on compact cinema cameras. The comparison matters because shared processing can change which settings a photographer can use while rigging, monitoring and shooting handheld with anamorphic glass.

What does open gate change on the FX5?

Open gate works on the FX5 only in Cine EI (a mode locked to one base ISO), and only when the camera records raw. Sony provides three base ISOs: 800, 4,000 and 12,800.

Raising the ISO above the selected base value brightens the monitor view but does not change what the camera writes to the card. The Canon EOS C50, which Gugliotta has used as his main camera for the past year, can record open gate in compressed H.265; the FX5’s restriction means bigger files every time.

That difference belongs in a storage and post-production plan before a rental or purchase. A photographer moving between the two bodies cannot assume identical open-gate handling.

How do Sony’s ISO modes affect workflow?

Sony gives the FX5 two other ISO modes. Cine EI Quick rolls over to the next base ISO as the photographer climbs past a threshold, while Flexible ISO applies real gain when the setting changes, an approach much closer to Canon’s handling.

For a larger production, a hard-locked base ISO protects footage if someone bumps a dial between takes. For a solo operator moving quickly, setting 1,250 and receiving a file at that exposure removes an edit step.

Cine EI would instead leave the operator pushing 800-footage up by two-thirds of a stop. The mode choice therefore follows crew size and shooting speed.

Can desqueeze, stabilization and autofocus work together?

Turning on anamorphic desqueeze switches off both the FX5’s sensor-shift stabilization and its digital stabilization. In Gugliotta’s test, it also disabled autofocus through the Tilta autofocus PL adapter he was testing.

The C50 retains digital stabilization and autofocus with desqueeze enabled. Consequently, the three features that drew Gugliotta to the FX5 do not all work together on that body.

The limitation is especially relevant to handheld work with anamorphic glass. Stabilization, monitoring and the lens setup have to be planned as one rig rather than selected independently from a specification sheet.

How much raw data does the FX5 produce?

At 5K open gate, Sony’s most compressed new raw option writes about 429 Mb/s (megabits per second), roughly one bit of data per pixel. That figure represents less data per pixel than any of the C50’s raw options, even after accounting for Canon’s larger 7K sensor.

Gugliotta’s Vancouver Island clips came in around 435 Mb/s, about three times the 150 Mb/s produced by typical 4K H.265. He found that “the most compressed option was more than enough for his work.”

The FX5 can record raw below full sensor resolution; the C50 records raw only at its full 7K. An accompanying video presents Gugliotta’s assessment of the FX5’s 16-bit raw files.

What should a photographer test before buying?

Manufacturers once reserved open gate for high-end cinema bodies such as the Sony Venice. Over the past couple of years, the feature has moved into smaller and cheaper cameras, including the Canon EOS C50, Panasonic Lumix S1II and Panasonic Lumix GH7.

Nikon says the upcoming Nikon ZR will gain open gate and anamorphic desqueeze through firmware. Because these modes share a processor, heat budget and sensor readout, enabling one can restrict what the others can do.

Gugliotta’s practical recommendation is direct: “Treat your shooting setup as a stack rather than a list.” A rental test should therefore use the exact codec, aspect ratio, stabilization, autofocus and monitoring combination planned for a typical workday.

This turns a feature checklist into a compatibility check before a business commits capital to a body. The next checkpoint is Nikon’s promised ZR firmware, which may bring another combination of these modes to a compact body and make that test even more important.