Mon Jan 17, 2022 12:20 pm
The Sony A7S III and FX3 (and most of the Sony Alpha cameras for that matter) do not actually output 1080p30 over HDMI when set to record at that resolution internally. Instead when set to 1080p HDMI output and 1080p30 internal recording, the camera will output 1080p60 (or technically 1080p5994) over its HDMI output.
This is a problem when using these cameras with the DeckLink Mini Recorder or the original, non-3G version of the UltraStudio Mini Recorder as these devices cannot handle 1080p60 input resolutions. They can only handle progressive resolutions up to 1080p30 or interlaced resolutions up to 1080i60. You would need something like the DeckLink Mini Recorder 4K or UltraStudio Mini Recorder 3G or better in order to handle 1080p60 input.
Alternatively, if you set the camera to record internally at 1080p30 and output 1080i60 over HDMI, with proper de-interlacing to combine the two fields for each frame, you should be able to convert the 1080i60 back into clean 1080p30.
This situation of outputting 1080p60 when recording 1080p30 internally is not unique to Sony cameras, but also affects a variety of consumer-oriented cameras from Canon and other manufacturers as well. I believe the reason for this behavior is that 1080p30 (or 1080p2997) was never a broadcast standard for HD video (like 1080i and 720p were), and as a result, many monitors and TVs do not support this as an input resolution. In contrast, 1080p50, 1080p60 as well as 1080p24 are all included formats in the AVCHD 2.0 video standards, which meant that these video formats are supported by a lot of Blu-Ray and other media players and enjoy better compatibility among HDMI monitors and TVs.
This is why some of these cameras are capable of outputting 1080p24 (or 1080p23.98) over HDMI as that is a popular video format for movies, but they do not do the same for 1080p30.