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Interlace or progressive mode when shooting 24p?


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#1 jeremyg

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Posted 10 December 2005 - 10:01 PM

The shop where I do most of my work is the proud owner of a new SDX900. While we need to go through some trial and error on setting up the menus, I was wondering how we should set it up if we are shooting 24pN (or 24pA). We don't have a deck as it's backordered and can't check this myself. I notice there's a menu to either shoot interlace or progressive. My inclination seems to want to turn it to progressive, but it defaults to interlace even when I select 24p mode, which seems to me I'd be shooting progressive and not interlace. The manual doesn't say much and refers to shooting at 25p, which isn't even an option on this camera. It also says that when it's turned to progressive, it is shooting true progressive but stand to lose resolution if the V.Detail isn't set to 0. Can someone please explain this to me? I want to shoot progressive, but I don't want to lose resolution doing so. What happens if I turn the camera to 24p mode and shoot interlace? Does this mean that I don't get true progressive frames? I'm kind of confused on this matter.


Thanks for your time.

Jeremy
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#2 Gordon Highland

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Posted 11 December 2005 - 12:52 AM

You should leave it on interlace if you're just shooting for video, maybe progressive if outputting to film. You're referring to the Vertical Resolution setting, right? (I think that's what it's called, I don't have my camera in front of me.) Supposedly the image can get a little buzzy if set to progressive when shooting progressive. It's been explained in one of these forums before.
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#3 jeremyg

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Posted 11 December 2005 - 03:54 AM

Thanks for the response, and what you said is what I gathered from the information that was handed over to me at purchase. The manual states the when in shooting in 25p and switched to progressive mode, progressive segmented frames are produced (PsF). I left the camera set to interlace as it's now out on a shoot, and I'll deal with the footage when it gets back. For next time, I'm just wondering how to proceed. When leaving the camera in interlace and shooting in 24p mode, do I not get progressive frames? The setting is V.DTL, not Vertical resolution. You mentioned a forum where this has been explained and/or discussed. Do you know which forum? Thanks again for your time.


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#4 Tim J Durham

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Posted 11 December 2005 - 04:44 AM

Thanks for the response, and what you said is what I gathered from the information that was handed over to me at purchase. The manual states the when in shooting in 25p and switched to progressive mode, progressive segmented frames are produced (PsF). I left the camera set to interlace as it's now out on a shoot, and I'll deal with the footage when it gets back. For next time, I'm just wondering how to proceed. When leaving the camera in interlace and shooting in 24p mode, do I not get progressive frames? The setting is V.DTL, not Vertical resolution. You mentioned a forum where this has been explained and/or discussed. Do you know which forum? Thanks again for your time.
Jeremy

The easy way to remember how to set it is by thinking where it will be shown. If it's for broadcast then it should be set to interlace. If it's for internet, progressive scan monitors/projectors or film-out it should be set to progressive.
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#5 David Mullen ASC

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Posted 11 December 2005 - 11:57 AM

The PAL version of the SDX900 camera ALWAYS records in interlaced-scan (50i). If you set it to 25P, it is capturing in progressive-scan but recording to interlaced-scan. You don't need a pulldown to convert 25P to 50i for recording.

The NTSC version always records in 60i. So it can't shoot at 25P, only 24P or 30P (and 60i of course). At 24P, it needs to use a pulldown (normal or advanced) to convert to 60i.

The "switch" you have been talking about has nothing to do with capturing in progressive versus interlaced, only with the amount of vertical detail. If you are shooting in progressive-scan mode and plan on displaying the image on a progressive-scan system OR do a transfer to film, you can allow a higher level of vertical detail, but if this recording is shown on an interlaced-scan monitor, you will get "twitter", high-frequency detail aliasing artifacts at the TV's raster lines (when shooting objects with fine horizontal details). So if the end result is only for interlaced-scan display, you'd want to reduce that vertical detail.

Now if the project is for both a film-out and interlaced-scan display, you may need to shoot with the progressive-scan level of vertical detail and then make a separate master after editing just for home video that has been put through an anti-aliasing filter.

Edited by David Mullen, 11 December 2005 - 11:59 AM.

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#6 jeremyg

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Posted 11 December 2005 - 12:54 PM

The NTSC version always records in 60i. So it can't shoot at 25P, only 24P or 30P (and 60i of course). At 24P, it needs to use a pulldown (normal or advanced) to convert to 60i.


It's an NTSC version, that' why it was weird that the manual was talking about shooting in 25p. Maybe it's a typo. Thanks for the explanation. I know what is involved in pulldowns, and the difference between Normal and Advanced. I was just confused by shooting 24p in interlace mode, versus 24p in progressive mode. Didn't know there'd be a difference. Sounds like it's better to leave it interlace for our purposes. None of our work goes out to film, but it does go out to web, and perhaps some progressive displays and computers. It does get projected now and again in large venues, but it's all off of video and not film. For the most part it's probably shown on regular old TVs, and laptops. When the camera gets back to the shop and our deck finally comes in, looks like I'll have to set it up and test for myself to see what the heck is really going on.


Thanks a lot for the post, David.

Jeremy
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