The F55 (and F5) are lacking cache or prerecord buffer, making it far from perfect for wildlife filming. I am considering to use a F55 with onboard filming 4K XAVC and attaching a nanoflash to capture 3 seconds cache in HD. Is this possible, 4K in camera and output to nano in HD?

SDI main output is HD 1920x1080, or you can configure the SDI(sub) and HDMI to output HD.

Just make sure 4k SDI/HDMI out is disabled in the menu.


One point of consideration however is how the F55 will treat the HD version of 4k since they have slightly different aspect ratios. Will the HD version be slightly letter-boxed like I have seen in post taking 4k down to HD? (ie. very thin bars on top and bottom) or will the F55 crop the sides by 128 pixels total to fill the frame vertically? I don't have an answer to that.

You can choose how the down conversion is done in the output format menu. LB or 16:9 Crop.