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1080i Revisited

The faster that images can be sequentially projected, the higher the quality By Ron Johnson
Sony HDW730
There seems to be a growing bandwagon for progressive scan high definition video production. Much of the decision-making appears to come from our filmmaker associates who have a long history of 24p acquisition that has produced a ?look that has become associated with high-end films, commercials and documentary work. These filmmakers are heavily invested in this ?look, and the equipment needed to achieve it.

Curiously, the 24 fps speed was originally derived as being the minimum speed that film could travel over an optical reader head in the camera and produce adequate audio for recording and playback. Yes, in fact this 24fps speed is a throwback to the days of the first ?talkies, and even with the advent of synchronized magnetic tracks the 24fps speed has remained unchanged.

In actuality, the faster that images can be sequentially projected on a screen, the higher quality (and reality) that can be achieved. Bandwidth and higher persistence of vision has always been an undisputed determining factor for creating realism for the moving projected image.

While interlaced images do introduce slight artifacting due to timing discrepancies between the odd and even fields during horizontal screen motion, these distortions are minimal when screen motion is slow much as it is in traditional film-like production. These artifacts are further reduced by the increased resolution due to the additional (and therefore smaller) scanning lines. In fact, high speed horizontal motion in 24p production (at 720 horizontal lines) can produce even more disturbing motion artifacts as the time interval between subsequent frames is longer allowing for greater ?jumps in motion continuity.

Sony half-inch formats are based on the tried, true and robust Betacam format that produces significantly more bandwidth than the Panasonic -inch format. Also, the -inch format is likely to be far more susceptible to the annoying drop-outs that are much more common with narrower tape widths. And the Panasonic format only produces 720 horizontal lines compared to the 1080 lines coming from the Sony cameras.

Panasonic AJHDC27 Varicam
Please dont get me wrong I think that the Panasonic VariCam is an excellent product, and its variable cranking speeds are to be envied. And many will say that 720 lines are more than adequate for delivery on HDTV. But common sense dictates that the more lines projected, the better the picture quality will appear. It is also a more technically reasonable solution to downconvert from 1080i to 720p than vice versa.

Today there are several software products that will enhance both 720p and 1080i when post-production is accomplished using computer-based editing systems. One of the most popular is the Magic Bullet software that can actually remove the interlace artifacts from 1080i footage to the point that one would be very hard pressed to identify the original interlaced acquisition format. This software has been used in numerous motion pictures to ?enhance standard interlaced video to be intercut into film projects on movies that Im sure, you the reader, have seen and been completely fooled by. Furthermore, the software can emulate a large variety of film stocks that will fool all but the most highly trained film craftsperson as to the actual origination source, and when delivering on HDTV (as opposed to the big screen) could be considered imperceptible. With the common use of desktop post-production systems and HDTV distribution, these points cannot be overlooked. In fact, certain ?treatments can be added to the HD material that can greatly enhance the look and feel of the finished project, all the while maintaining the HDTV quality of the original source.

One last consideration is the Sony CineAlta camera that can shoot at 1080p. This may very well be the ultimate camera for the next generation of bonafide film makers, but remains out of the financial reach of the independent producer who is working in documentary, industrial and broadcast venues. The CineAlta has none of the shortcomings discussed previously in this article, as it can shoot at variable frame rates in full progressive modes. But, until I can afford a camera that starts at approximately $100,000.00 (without a lens), Im inclined to look into the Sony HDW730 which is capable of both 50i and 60i production very handy for those of us who produce material in the U.S. and overseas. The off-speed and faux progressive scan looks can be handily achieved on my computer based editing system in a way that is indistinguishable for HD Plasma screens.

Ron Johnson is a videomaker with over 20 years' experience. Currently working as a video and digital media producer in Saudi Arabia, Ron has worked at WXYZ-TV (Detroit), KRON-TV (San Francisco) and Tektronix, Inc. (Beaverton, OR) He has earned eight Emmy awards from 17 nominations, an Iris and Peabody award nominations, and special recognition from the United States Drug Enforcement Administration.

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Related Keywords:1080i, progressive scan, high definition, video production, 24p acquisition


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