On Mon, 2022-08-01 at 07:11 +0100, Barry wrote: > That is usual, it’s called 60 but is in fact the NTSC refresh rate. > It’s offset from 60Hz to avoid flicker effects from lighting I > understand. If it was exactly the same as mains, you'd get no flickering effects (the very slow phase differences would be very minor). If it's a slightly different frequency, that's when flickering can be more noticeable. NTSC isn't exactly 60 Hertz because they wanted a precise relationship between vert and horizontal sync, and colour subcarrier and sound subcarrier with minimal interference between each other. Think of it like a series of cogs meshed together, rather than a number of free- running motors *trying* to spin precisely in time with each other. NTSC is almost 60 Hertz because it's barely any different from the B&W 60 Hertz system before it. It was 60 Hertz (same as mains frequency) to avoid flicker with the mains powered lights. Back then, some cameras were quite sensitive to such things. Much more than people might notice mains hum issues on their television sets. 50 Hertz countries got 50 Hertz television for the same reason. I've often wondered what film studios did. Did they use DC lights? Did they have special AC generators running at a multiple of film frame rates? Film's normally shot at 24 frames per second. I know 60 Hertz cameras don't like our 50 Hertz lighting, I've had to film under those circumstances and the strobing can be migraine-inducing. I can't imagine filming at 24 Hertz under 60 Hertz lighting would be any better. -- uname -rsvp Linux 3.10.0-1160.71.1.el7.x86_64 #1 SMP Tue Jun 28 15:37:28 UTC 2022 x86_64 Boilerplate: All unexpected mail to my mailbox is automatically deleted. I will only get to see the messages that are posted to the mailing list. _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
