A common limitation with newer (and generally more affordable) cameras is that higher frame rates require a crop mode. Sometimes this is minor, like how the a7S III crops in 10% for getting 4K at 120 fps, and other times it’s a significant change, like the a7 IV featured here which requires Super 35mm for 4K at 60 fps. There just might be a solution for the a7 IV’s crop.
Gerald Undone may have discovered a workaround or hack that allows you to record 4K at 60 fps with the a7 IV without any crop. It’s very interesting and might be useful for you.
To try this out you will need an external recorder such as the Atomos Ninja V. It is weird behavior relating to the a7 IV’s HDMI output. In the camera’s settings if you set the output resolution to 1080p you can easily set the frame rate to 60p.
Then, if you head back to the resolution you can set it to UHD 4K 2160p. The Ninja V will actually appear to read this as 4K at 60p without any crop.
Is this all true? One question, even if the files appear to be 4K 60p, is whether the camera is doing an upsampling from the original 1080p setting.
Gerald enlisted iPhonedo to do some tests with the camera. It is true that you will end up recording 4K 60p footage with this combination of settings. However, compared to the internal 4K recording you can get the external footage just doesn’t have the same degree of detail. It definitely looks like the “hacked” 4K footage is upsampled 1080p footage.
However, the upscaled 4K footage does look better than native 1080p footage. It is still probably best to do this type of move in post anyway and it’ll save you the trouble and file sizes.
Anyway, it doesn’t seem like you actually get true 4K at 60 fps with no crop. You will get high-quality 4K 60p footage in the crop mode though, so don’t rule out the a7 IV unless you just can’t get by with any crop mode. In that case you should go with the numerous other camera options, like the a7S III, which can do 4K 60p and above with no crop.
[source: Gerald Undone]