Shutter speed - hdmi/sdi output frame rate

Hi,

I've noticed that many of the cameras I've used with hdmi or sdi outputs seem to be locked to either 50 or 60(59.94) fps. This is still the case even if the camera is recording at 24/25/30 etc.

My question is - if trying to stick to 180° shutter speed, how do I setup the cameras for simultaneous recording and streaming if there are 2 frame rates to consider. Do I set it at 1/50 for 25p recording, or will this result in too much motion blur for the 50p that's going to the switcher? Running at 1/100 is undesirable since we often film in low light.

I should point out that I'd prefer to go 25p direct from the camera, but a lot of the lower budget cameras I've used (Canon C100 for example) don't support this so I send everything to the switcher at 50 frames then down-convert for the stream.

Thanks for any clarification,

Mike

Use the shutter angle for the 1080p25recording. The camera is actually outputting 1080i50/59.94 interlaced fields, not 50/59.94fps. It takes two fields of interlaced signal to get one frame.
Cheers

Great, thank you. I thought that was the case but wanted to clarify.

So is it always as simple as using (to stick with 180°) 1 / 2*frame rate) for progressive and 1 / field rate for interlaced video?

As far as using 50i in an ATEM switcher with the intention of recording/streaming a 25p program, is there a significant loss in quality? And is it better to convert each camera on the way into the ATEM and run it at 25p or run everything at 50i and convert as the last step out of the switcher? I believe some cameras even output 50psf so could be 'converted' into the atem with no loss of quality.

Many thanks for the help,

Mike

It would be simpler and better to run the cameras at 50i and convert back to 1089p25 at the ATEM output.
This would only require one converter.
Cherrs

Yep, makes sense to me (I assume you meant 1080p25!!).

Thanks for the help,

Mike