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1080i/24p with reduced resolution?
Just tried to find from manual if there’s a setting in hvx200 for “V DETAIL FREQ” in 1080i mode?
If there isn’t, does this mean that 1080p24 always has reduced vertical resolution to remove line flicker from interlaced displays?
Or does this even matter if the camera does not have more real resolution in 1080 mode than 720 mode? -
18 Replies
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[toke lahti] “Or does this even matter if the camera does not have more real resolution in 1080 mode than 720 mode?”
Ouch, dude. Wait until the tests come back… we’re all concerned, but nothing’s been quantified yet.
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[toke lahti] “Just tried to find from manual if there’s a setting in hvx200 for “V DETAIL FREQ” in 1080i mode?
If there isn’t, does this mean that 1080p24 always has reduced vertical resolution to remove line flicker from interlaced displays?”One has nothing to do with the other. Why? why should a progressive image have less detail than the interlaced content from the progressive capture. The camera has a 1080p imager. it starts as a progressive image.
ga
Gary Adcock
Studio37
HD and Film Consultation
Chicago, IL USA -
It doesn’t matter what the imager is, video has to be vertically filtered to stop interlaced twitter if displayed on a CRT. Most cameras that shoot progressive allow you to turn off the filtering on progressive images if you’re, say, going for film out, or are never going to display on a CRT. Toke’s question is a good one.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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[gary adcock] “One has nothing to do with the other. Why? why should a progressive image have less detail than the interlaced content from the progressive capture. The camera has a 1080p imager. it starts as a progressive image.”
So do dvx100 have progressive imager.
Both have “V DETAIL FREQ” setting when shooting 480p.
With that setting you can reduce vertical details so that there’s no 30 Hz flickering of the details in interlaced display (like regular crt TV).And because there’s no setting for 1080i mode, it makes me wonder if
1) vertical resolution is always reduced, or
2) vertical resolution is never reduced and if 30 Hz flickering of details disturbs you with interlaced monitor, it’s just too bad, or
3) camera’s lens & imager combination produces always so soft picture that there will be no 30 Hz flicker anyway.And no, camera does not luckily have 1080p imager. Each ccd has less vertical pixels than that. It is adverized to have “1080p block”. If every ccd had 1080 pixel vertical resolution, each pixel would be so small, that the noise would be horrible.
And recent posts in various forums show resolution charts that suggests that the camera’s real resolution is about 600×600. Like Steve Mullen said, you can get a camera for $2k with resolution of 600×500.
I’m starting to think do I want to pay 8k more for 20% more resolution and 16:9 AR… -
>toke lahti:”Just tried to find from manual if there’s a setting in hvx200 for “V DETAIL FREQ” in 1080i mode?
You won’t find it there, it is always Blue(that means it is not a valid choice)
>If there isn’t, does this mean that 1080p24 always has reduced vertical resolution to remove line flicker from interlaced displays?< The flicker is not what it removes. Let's back up here. The NTSC monitor can show about 380 lines of resolution, the DVX100 can record about 450. If you put that much resolution into the 380 lines you can get a lot of aliasing and noise in that overly detailed area. So we put in the Thick/Thin filter. It is used for back down some of the resolution for an NTSC/TV out. End of chapter one against TV technology that was invented in the late 50's/60's. Let's move forward to HDTV. This "too much resolution" is not an issue and thus to limit the resolution is ridiculous because the technology and resolution in these sets can handle it. The sophicticated filters that are in the sets, jut roll it off instead of making it a mess, or at least the better known brands do. >Or does this even matter if the camera does not have more real resolution in 1080 mode than 720 mode?”
There is more resolution on the HVX in 1080i than there is in 720P horizontally anyhow.
Best regards,
Jan
Jan Crittenden Livingston
Product Manager, DVCPRO, DVCPRO50, AG-DVX100
Panasonic Broadcast & TV Systems -
Jan, all interlaced systems suffer from interlace flicker/line twitter. Take a HD CRT monitor and put unfiltered video through it, it flickers, just like NTSC on a TV or PAL on a TV. It’s a problem inherent in interlaced systems. Hence why 1080i has no more vertical resolution than 720p, because it has to be filtered. Now, most HD televisions are inherently progressive, but there’s still a large number of interlaced CRTs out there that need the filtering. Call it flicker or interlace twitter, it’s an issue. I’ve never known any CRT perform any interlace filtering as it’s always assumed that the broadcast signal is pre-filtered. If the CRT filtered, we’d never need to pre-filter our computer generated graphics before we add them to a video, but we do need to pre-filter our graphics.
“You won’t find it there, it is always Blue(that means it is not a valid choice).” Does that mean there’s a menu choice that’s never choosable? If so, then that’s ludicrous.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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Graeme,
If you read my post, the function is not about twitter, but rather too much resolution that turns into aliasing. HDTV montiors have the resolution and thus the problem of too much reslution goes away.
>interlace twitter, it’s an issue.
I never said it wasn’t. The Thick/Thin is not about twitter at all, it is about too much resolution being sent to a SD monitor than cannot display it and thus, turning it into garbage.
>Me:You won’t find it there, it is always Blue(that means it is not a valid choice).” Graeme:
Does that mean there’s a menu choice that’s never choosable?
If so, then that’s ludicrous.Graeme if you ever worked any of the DVX100 camera you would know the situation and how the camera worked. A blued out menu is non-relevant to the mode you are in. Frankly to have the item drop out of the list would be a programming nightmare for the engineers on this camera. Because not only would there be a need to drop the menu item but then to make sure that nothing else dropped and then to be sure that it came back in in all of the other modes that it was relevant to.
Thanks,
Jan
Jan Crittenden Livingston
Product Manager, DVCPRO, DVCPRO50, AG-DVX100
Panasonic Broadcast & TV Systems -
So that blued out control is only valid for certain modes, and in modes that it’s not relevent for, it’s blued out? Thanks for the clarification, as I’d got the misunderstanding that the menu item was just permanently blued out, and hence never choosable. I’d guess it’s choosable in the SD modes?
Reading in the HVX200 manual from the link you kindly posted, the description of the effect of thick/med/thin in “480i progressive mode” is exactly the description of interlace interline twitter.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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Graeme Nattress:So that blued out control is only valid for certain modes, and in modes that it’s not relevent for, it’s blued out? Thanks for the clarification, as I’d got the misunderstanding that the menu item was just permanently blued out, and hence never choosable. I’d guess it’s choosable in the SD modes?
That is correct.
Reading in the HVX200 manual from the link you kindly posted, the description of the effect of thick/med/thin in “480i progressive mode” is exactly the description of interlace interline twitter.
Can’t help that, I have never seen anything that gets rid of interline twitter. Have you? It is a translation thing, it is about excessive resolution on an SD monitor looking really awful, and maybe it, in some cases, looks like more excessive interline twitter, and that is where the the description came from, but it is a filter that filters off the top end of the resolution.
Best,
jan
Jan Crittenden Livingston
Product Manager, DVCPRO, DVCPRO50, AG-DVX100
Panasonic Broadcast & TV Systems -
Excessive vertical resolution causes interline twitter on interlaced systems. To get rid of it, you reduce vertical resolution to about 70%. This has been done since the dawn of television.
From Poynton pg56 “twitter, a small scale phenonemon that is percieved as scintilation, or an extremely rapid up-and-down motion…. ….Twitter is produced… …from high contrast vertical detail in ordinary images. High quality vide cameras include optical spatial lowpass filtering to attenuate vertical detail that otherwise be liable to produce twitter.” I’ll add that with progressive cameras, where you don’t always want the spatial filtering to be there, you can do it after the CCD on a software switch. “when cgi is interlaced, vertical detail must be filtered in order to avoid flicker. a circuit to accomplish this is called a twitter filter”.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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