I went out and took some videos in the past weekend. With 3072x1308, 23.976FPS, I was able to get continued recording. Struggled a little bit when the card was almost full. And I upscaled to 4K in post-production. Looks very usable for me. And I think I can get 3520x1320 continues now. Will do more test videos.
Here was my setting:
EquipmentCamera: 5D Mark III with 17-40mm F4. (with 24-70mm L F2.8, sometimes can't get continued
recording)
SD Card: SanDisk Extreme Generation 1, class 10 45MB/s. Magic Lantern installed in this card
CF Card: Lexar Pro UDMA7 1066x 128 BG. Video recorded in this card.
Canon Menu setting:Auto Lighting Optimizer: OFF
MOvie Rec. Size: 1920 24 ALL-1
Long Exp. noise reduction: OFF
High ISO Sped NR: OFF
Highlight Tone Priority: OFF
Magic Lantern setting:Crop_rec for 4K Raw Video Recording installed.
Here is the original post by a1ex
http://www.magiclantern.fm/forum/index.php?topic=19300.0Download link here
https://builds.magiclantern.fm/jenkins/job/crop_rec_4k/36/artifact/platform/5D3.113/magiclantern-crop_rec_4k.2017Jun19.5D3113.zipModules: enabled "crop_rec", "mlv_lite", "mlv_play" (remember to restart the camera after enabling)
Overlay: enabled "Zebras", "Focus Peak", "Spotmeter", "Histogram"
Movie: enabled "Gradual Exposure", "FPS override 23.976", "Crop Mode 3K 1:1", "Raw Video 3072x1308 2.35:1, 14bit lossess"
Recording with M mode, 1/50 sec, ISO 100, F 11