prograssive vs. Interlaced at

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Sony HVR-Z1 / HDR-FX1
Pro and consumer versions of this Sony 3-CCD HDV camcorder.

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Old May 14th, 2005, 08:49 PM   #1
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prograssive vs. Interlaced

i'm trying to make up my mind in this age of confusion on what kind of cam to buy.

i am a newbee but with a big passion and willing to learn and want to get the z1 but what i hear is that fast action is not liked by the interlaced nature of the z1. pass that i use slowmotion a lot on my projects, with these said
--how do the differences on P and I effect my shooting.
I am sorry but i'm not familiar with the differences of these formats.
I have also read that with shooting interlaced footage fine fonts that are thing dont show up right or are hard to read and also in at the end of the output there might be a noticeable flicker due to the interlaced footage.
--is it possible to convert from interlaced to progessive. will it take a long time to convert your clips?
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Old May 15th, 2005, 05:23 AM   #2
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You're right about the age of confusion, Dan. Almost nothing you say can be absolutely true anymore. But I'll take a shot at your question. Shooting 24p was the answer to the desire of filmmakers to shoot video that was both closer to a film look and could be transferred to film without converting 60 fields to 24 frames. For the same reason some producers chose PAL cameras regardless of where they lived and worked because shooting 25 fps made film conversions easier than with NTSC source material. Both PAL and NTSC standards require interlaced material because tv's display fields versus frames, ironically in order to reduce flicker on screen. It's my understanding that if you edit 24p in most NLEs, it is converted to 29.97 fps (NTSC) in the capture process, and if the editor allows it, converted back to 24p on export. I'm shaky on that because I have no personal experience with it.

You can deinterlace in post production but the majority of users who do so are creating output for a computer screen, such as Internet video.

Hopefully others will step up to fill in the holes and correct the mistakes in my reply.

David Hurdon
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Old May 15th, 2005, 09:28 AM   #3
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This is a simple explanation , I Hope!!! THe PAL and NTSC CRT TV's use an interlacing scheme to display the images that one sees. SCanning the ODD and Even horizontal lines in two distinct scans ( those are the lines that one sees going across the display on older TV's). It was done for all sorts of technical reasons of available bandwidth and cost etc, but its what we have now. IT was conceived to fool the viewers eyes in two ways, the decay in the screen phosphors and the way our eyes perceive motion( our brain fills in the gaps). The farther away one sits from a CRT TV the better it looks. IF one needs a big TV , relative to viewing distance, then the viewer will see the lines for sure, and the picture will not look so good. The cameras that are interlaced create a stream of video that matches the TV so in NTSC capture a field of ODD or EVEN lines every 1/60 sec. The field images are thus taken a 1/60 sec apart and are thus able to capture most motion smoothly as perceived by the viewer on a CRT. Clearly for anything moving there is a difference between the two fields in the 1/60 sec and analysis of the two field images on a PC progressive display can be seen. The 1/60 rate was choosen because above that level our eyes cannot easily see flicker in the image which is the problem with very fine horizontal lines ( for instance in fine text) on an interlaced display as these are often dominant in only one field and thus appear to display at 1/30 sec frame rate well in the flicker range for our eyes.
Progressive takes full frame images at whatever rate is choosen. at 24P then 24 images are taken every sec to match the frame rate of a film camera and as has been said allow easy transfer to film for projection or display on a PC. The images will be nice and sharp governed by the shutter speed choosen for exposure. The problem is that fast motion will stutter since only 24 frames are being taken a second( as opposed to 60 fields of interlace, the interlace image has 2.5 times as many images taken in the same time, all be it at half the vertical resolution). Increasing to 30P will improve the stutter ( interlace will still have twice the images)but will only give the perceived motion flow of interlace at 60P in which case the image will be far superior to interlace in both sharpness and motion flow.
Most projection TV, LCD and Plasma all convert the interlace video to progressive for display( refreshing at 60hz or above) and clearly the electonics to deinterlace play a big part in how good this final image really looks. Based on the input it can look really good or just plain terrible.

If you want fast motion that flows on the screen then your choice now is interlace viewed on a CRT. In the future one hopes that 60P cameras will become available and we can finally move into the era of crisp smooth motion images.

Ron Evans
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Old May 15th, 2005, 10:46 AM   #4
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It's worth remembering that 1080i footage at 30fps can be considered to be 540p at 60fps. So if you want half-speed slow motion, you can split out the fields and interpolate vertically, giving you a lower resolution but true 60fps footage... it's one of the few benefits of shooting interlaced over 30fps progressive :). If you shot 30p, you'd have to do some weird tricks to try to make up frames between those you shot, which rarely looks very good, in my opinion.
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Old May 16th, 2005, 08:44 AM   #5
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these being said, then my understanding is that editing on flatpanel LCD monitors will not give me a desireable look while i'm working with the footage. either SD or HD and the TVs that transform the image to prograssive then probabely have to be really good TVs to do this job well. so what is the advantage of working with these z1 cameras? we have no option of prograssive neither in DV or HDV and the images are "wierd". am i understanding this correctly?
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Old May 16th, 2005, 08:51 AM   #6
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The display doesn't "transform" anything.
You can use a progressive intermediary and color correct on an LCD monitor, in fact, I recommend it. Because *most* HD media will be viewed on LCD and not CRT, you might as well be color correcting for the display device.
Yes, an HD CRT is best, but not absolutely essential/critical.
Douglas Spotted Eagle/Spot
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Old May 16th, 2005, 02:08 PM   #7
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IN simple terms if you want to capture fast motion AND do slow motion in post then interlace is what you want now for your camera. IF you do not need HD right now then you can avoid any of the MPEG2 possible artifacts by using a high quality DV camera. The FX1 and Z1 can do both DV and HDV. The ideal would be a progressive camera with 60 frames a second capture or above. It just doesn't exist for consumers/prosumers at this time. Most NLE's will allow you to edit and output a progressive stream if that is what you want. JUst as Douglas has said most output these days will be watched on PC monitor , LCD or Plasma and its always good to monitor the editing on the expected viewing device.

Ron Evans
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