I'm trying to use an external monitor with my xf400 and for some reason it only works when my video resolution is set to 3840x2160 or 1280x720(8 mbps). If I set it to any of the 1920x1080 modes except for 59.97 it will not display to my monitor. I have tried 3 separate monitors at this point and the same type of thing is happening. I have used the monitor with other 4k cameras in both 4k modes and FHD modes and the monitor works fine. I'm using the Feelworld F6 plus. Has anyone else had this problem?

I have the same problem with several monitor brands (Lilliput, tvlogic etc.). 1080p with 25p doesn't work, 50p works.
I had contact with Canon Germany about this issue. Canon insists that they adhere exactly to the HDMI specifications and that the problem is with the manufacturers of the monitors.
Atomos Shogun monitor has no problem with the XF400 1080p25 HDMI signal.

If the issue is the same as the one that plagued people when the Canon C100 series came out it may well be the fact that the output is not a true 25p from the XF400 but 25PsF.

Progressive Segmented Frame is actually 25 frames, or 30 in NTSC terms, but stored as 2 fields per frame. The reason this was done some years back is that the good old analogue CRT TVs could not handle true progressive frames but could handle 25PsF as they would see the signal as Interlaced and be able to play the images. The thing is these days a lot of later model progressive monitors will not decode two field PsF 25/30 frames per second footage. It should be easy enough to dissect a piece of your footage to see if it is PsF. The Atoms monitor/recorders will see and decode PsF that's why one of you is having no issues with the Atomos.

https://en.wikipedia.org/wiki/Progressive_segmented_frame

Chris Young

The Canon C100 MkII outputs a 1080i 50Hz signal via HDMI when set to MP4 recording at 25p. This 1080i signal is no problem for the Lilliput monitors.
The XF400 outputs a true 1080p25 (progressive) signal. A few monitors understand it, many others don't. As I said: Canon feels absolutely no guilt.

Keep in mind that there is no EBU 25P/1080 HDTV broadcast standard. Most high end monitor manufactures will design their equipment to comply with the existing standards. Nothing more and nothing less. There are undoubtedly monitor manufactures who make monitors that will handle true 25p progressive. Atomos for one. I use their 4k monitor/recorders mainly for 4K and HD 50p but they will take 25p and 25PsF and you can actually record HD 50i as 25PsF if you so wish.

Therefore cameras that produce 1080 25PsF 50 fields in a container qualify under the EBU specs for interlace output. These cameras will generally work with most monitors that have a compliant 50i input. Cameras such as the C100 Mk II mentioned have a compliant PsF output. A camera that produces an output that isn't an EBU recognized broadcast standard, such as true progressive 25p will not display an output signal if the monitor you are outputting to is designed specifically to meet EBU specs of which 25p is not one. Therefore I understand Canon's point of view.

I can understand why 25p on many cameras can be output as 50i for viewing as 50i is part of the broadcast standard. I use 50i whenever I'm monitoring a 25p shoot due to the fact that 25p monitoring isn't widely used in broadcast monitors. But very few people in production would use the 25p MP4 of the Canon with its highly compressed AAC audio for serious post production. The C100 Mk II mentioned when shooting 25p in MP4 only offers AAC audio recording. High bit rate LPCM audio at 50p, 50i and 25PsF is only offered in the AVCHD format. LPCM is part of the broadcast spec. AAC was developed primarily as a good but highly compressed delivery codec.

25p for broadcast has to be converted to 50i. I have to ask. Why do people shoot 25p? Some people reckon it has a supposed '25p film look.' The problem with that assumption is that progressive video has higher spatial resolution but lower temporal resolution at 25p, jerky motion instead of fluid 50i motion. Film on the other hand shot at 24fps is projected at 48, 72 or 96fps and has a much smoother cadence. Film has a totally different spatial and temporal look and motion cadence to the supposed 25p video 'film look.'

https://www.academia.edu/26998065/DLP_Cinema_projection_A_hybrid_frame-rate_technique_for_flicker-free_performance

Different EBU broadcast standards for Europe below. EBU standards as we appear to be mainly referring to 50Hz in these postings.

Chris Young

I’ve experienced similar issues with other cameras. Decimator sells scaler/converters but they’re pricey and you need to power and place an additional device between your camera and monitor. Probably better to put your money into a compatible Atomos monitor. I use Atomos, imagine quality is super and acts as backup. I don’t like spending money on peripherals but it’s the best investment I’ve made.