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-   -   60 fps vs 59.94 fps (https://www.dvinfo.net/forum/general-hd-720-1080-acquisition/104980-60-fps-vs-59-94-fps.html)

Ron Edwards October 4th, 2007 11:25 AM

60 fps vs 59.94 fps
 
I see 60 fps and 59.94 fps standards stated for video cameras. Are they the same thing?

Thanks in Advance!

Glenn Chan October 4th, 2007 01:46 PM

In NTSC countries, the frame rates tend to based off of 30 * 1000 / 1001... which is approximately 29.97fps. Double that frame rate is 59.94fps.
Most people say "p60" or "60fps" when they really mean 59.94fps, or "30" when they mean 29.97. Because saying 29.97 is somewhat unwieldy.

HOWEVER, film equipment will shoot at 24.000fps and some other equipment will shoot at exact frame rates (e.g. you could have timecode at 30.000fps). Because 29.97fps and 30.00fps are not the same, there are definitely sync issues to pay attention to.

In the video world, you don't have to worry about that as long as everything in your chain does 29.97 / 59.94fps, and you don't have exact frame rates in there (30.000fps, 60.000fps, 24.000fps, etc.).

Steven Thomas October 4th, 2007 02:30 PM

NTSC US standard is 59.94 field rate.

This change has been since the 50s with the introduction of color TV.
There was a small offset in frequency to make the chrominance sub-carrier compatible with black & white scan rate of 30 frames per second.

If your intention is for playback on a NTSC television, 59.94 is the choice.

Ron Edwards October 5th, 2007 10:51 AM

Bottom Line
 
So if I am reading your right .... even though my JVC 5100 states "60 FPS" it is actually running at 59.94 in NTSC land ?

Steven Thomas October 5th, 2007 01:53 PM

I believe that is correct.

Ken Hodson October 5th, 2007 03:52 PM

Quote:

Originally Posted by Ron Edwards (Post 754797)
So if I am reading your right .... even though my JVC 5100 states "60 FPS" it is actually running at 59.94 in NTSC land ?

I wouldn't imagine your 5100 says it is running at "60fps", I would think it would state it shoots "60i" which is the abbreviation for shooting 60 interlaced FIELDS per second which equates, as mentioned, to 59.94 interlaced fields/s NTSC standard.

David Heath October 5th, 2007 04:59 PM

Quote:

Originally Posted by Steven Thomas (Post 754429)
This change has been since the 50s with the introduction of color TV. There was a small offset in frequency to make the chrominance sub-carrier compatible with black & white scan rate of 30 frames per second.

Almost - the chrominance sub carrier has to be an exact multiple of line and field frequency to avoid patterning.

If the frame frequency had been kept at exactly 30Hz, the resulting chroma sub carrier was found to produce severe sound problems on some early sets, due to interfering with the sound subcarrier. This was solved by shifting the chroma subcarrier frequency - and hence the line and field frequencies by the same percentage.

A clever idea at the time, but has it given headaches since, in ways unimagined then - drop frame timecode for one.

Steven Thomas October 5th, 2007 06:49 PM

Quote:

Originally Posted by David Heath (Post 754946)
This was solved by shifting the chroma subcarrier frequency

.

This is what I stated. We could go into a lot of detail on this, it was only brought up as a simplified description why 59.94 field rate exists for our NTSC sets.


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