The purpose of shooting this video was to test Sony's 2K OLPF (optical low-pass filter) that is an optional accessory for the PMW-F55 -- while also using the camera's HFR (high frame rate) recording mode.
Like all digital cameras, the F55 has an Optical Low-Pass Filter (OLPF) that sits between the lens and the image sensor to suppress high frequency detail that can cause aliasing, moiré, and overly sharp images. Most cameras work fine with a single OLPF, but the F55 offers too many different shooting modes for a “one size fits all” filter to provided optimal results all the time. To address this need, Sony offers an optional 2K OLPF (CBK-55F2K) that will eliminate the moiré and aliasing that can sometimes occur when shooting with the full-frame 2K recording formats (not the “2K Center” scan mode). The 2K OLPF is a user-changeable filter that temporarily replaces the existing 4K OLPF that sits in front of the sensor. It takes less than a minute to change, and the two filters can be swapped back and forth as necessary.
The problem of aliasing is often most visible when the “S&Q Motion”, “High Frame Rate,” and “Full Scan” modes are being used all together. The more contrast and fine detail that are present in the image, the more chance you have of getting an aliasing problem. In this video, every shot uses the 2K OLPF and I don't see any unusual aliasing. However, a few of the shots also used the camera's "2K Center" scan mode at the same time. And those shots, look soft and muddy -- as I expected. But that's what testing is for.
For comparison, here's another video I shot that uses S&Q Motion”, “High Frame Rate,” and “Full Scan” modes , but NOT the 2K OLPF: vimeo.com/96412170
My conclusions are:
1) The 2K OLPF is recommended for full-frame HFR shooting.
2) 2K Center scan mode is a good alternative to using the 2K OLPF -- if you don't mind having your FoV cut in half. Sometimes that can actually be an advantage for wildlife and sports shooting. You essentially double your focal length with no loss of light.
3) Never use the 2K Center scan mode at the same time as the 2K OLPF.
Normally my VORTEX-1 scene file should not require grading, but most of this video was shot through a chain link fence and that washes out the contrast, So a little grading was necessary to bring back the proper contrast.
Format: XAVC HD / 23.98
HFR: 180 fps
Scene File: VORTEX-1 or S-Gamut2/S-LOG2
2K OLPF: Yes
Lens: Red 300mm T2.9
For more information about the Sony PMW-F55 camcorder, please see “Doug Jensen's Guide to the Sony PMW-F55” book.