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Producing in digital is sort of like producing in analog, except that the picture has the potential to be better--much better, and much worse. You might see things you've never seen before, just like hearing a favorite vinyl record or cassette tape on CD for the first time. Some of those things you'll see for the first time won't be good things either--compression artifacts, motion blur, bad 16:9 image composition, and a host of others.
To aid you in this endeavor, please see the digital video production and transmission charts in Appendix A: Digital Television Production & Transmission.
The real world is analog. What you shoot is analog and the way it will be displayed to the viewer is analog. But, as they say, "It's a digital world."
By Colette Connor
Use a cheap lens and your image will suffer. Use a great lens and your image will be great. Use a high definition lens and you'll spend a lot of money, though maybe not as much as you think. Improvements in the evolving technology of lenses have allowed lenses to become smaller in size and weight without sacrificing strength and optical quality.
Today, the best lens that you can buy for video is a high definition lens. And while you may be shooting in standard definition, you can still use a high definition lens if you think it is worth the cost.
The lens is what brings the image to the imager (a single CCD, an optical block with three CCDs, or even an optical block with three tubes). And this lens is an analog device that affects your picture quality first. If part of the image doesn't make it through the lens, it will never make it to the viewer.
Lenses, in fact, contain various elements, and many different kinds of glass are used in their manufacture: the type of glass chosen for a particular lens is designed to pass different frequencies of information, in the form of light waves, to the camera. The higher the resolution, the more information is being passed, and the more complicated and difficult the lens is to make.
The consensus of industry opinion is that as digital television defines itself, high definition (HD) lenses will come more and more into use. How expensive will HD lenses be? Will all HD lenses work with the myriad of proposed TV-line formats? How difficult are they to shoot with? What impact does aspect ratio have? Can you use HD lenses on 16:9/4:3 switchable cameras? Are there any benefits to using an HD lens on a standard definition television (SDTV) camera?
HD Lens Basics
Video camera lenses are designed and manufactured to complement the television system they operate in. The major difference between current NTSC lenses and HD lenses is the amount of information (such as the number of TV lines) the lens has to resolve. The current NTSC standard is 525 TV lines of resolution (480 are active). The higher definition lens, whether it is resolving 480 progressive scan (p), 720p or 1080 interlaced (i) TV lines, has to resolve more information.
In our present TV transmission system everything--including lenses--is referenced by the number of scanning lines and scan rate; 5 MHz, which relates to 400 horizontal TV lines, has been the standard since the beginning of U.S. television. NHK (see below) has recommended that the U.S. television standard be raised from the present 5 MHz for NTSC video up to 9 MHz for HD video, which will cover all of the new formats that are being proposed. Camera lenses that relate to higher scanning rates are already being produced.
16:9 Aspect Ratio
There is no mandate for digital broadcasting of 16:9 or high definition television. But--and it's a big "but"--consumer TV manufacturers are moving towards or are already producing 16:9 consumer digital TV sets. Only time will tell if consumers will buy the new shape of television. However, when you're talking high definition, you are talking 16:9 aspect ratio.
The granddaddy of HDTV is Japan's NHK television network. This is the "1125" system (shot, broadcast, and received in 16:9 aspect ratio) that is still used throughout the world by HD pioneers, experimental artists and high definition production companies that until recently produced programming almost exclusively for NHK. That high resolution analog "1125" system, with double the number of scan lines of NTSC (1080 active TV lines), calls for extreme attention to detail, especially in the lens. At 1080 TV lines, any deviation in the light results in one-quarter less allowable error in a lens than what is considered allowable error in any current SDTV lens. There's considerably less margin of error in color resolution.
Operationally, HD lenses will be used exactly the same as any lens, but visually--to the cameraperson or to the director--everything changes. Since HD lenses are designed right from start to do 16:9, framing is the first thing you'll notice. After that, the whole look of the system is amazingly crisp, and gives the viewer the feeling that they're right in the picture. Most viewfinders don't have enough resolution to show the difference, but on a monitor (typically at least 17 inches in diameter) everybody will see the difference.
Learning to shoot 16:9, everyone agrees, is practically back-to-school time. (See Framing for Two Worlds that follows.) Your lighting changes, the placement of your cameras change, your camera angles change. The sets have to change because they're going to be wider than they are tall--considerably. Focus also becomes an issue. An HD lens picks up such fine detail that instead of a tight close-up of a talking head, a medium close-up shot will be all the detail you'll need (or want).
A small but growing number of TV stations and independent production companies (particularly documentary producers, at the moment) are hedging their bets by shooting 16:9 high definition, mainly for archiving purposes. That way, their digital 16:9 production can be downconverted or upconverted to any aspect ratio or TV-line format; it's future-proofing their hard work.
HD Lens Manufacturing
The basic manufacturing process of an HD lens--from the initial cutting, grinding, and polishing of the glass through to the mechanical and electronic construction--is almost exactly the same as the SD lens process, but the quality control and the specifications are at a higher level. Improvements in the evolving technology of lenses have allowed lenses to become small in size and weight without sacrificing strength and optional quality.
There are over 200 types of glass that can be chosen for a lens (SD or HD) and in any one lens there can be several different kinds of glass. The glass is hand-picked to meet the specifications and the quality needed for high definition. Starting out with a block of glass that looks like a big ice cube, it is then cut into the general shape--a little larger than needed--and then ground into the exact shape desired. The polishing process then begins, from coarse to fine, to finer, to ultra-fine. After that, every element in every lens is coated. For HD lenses, the coatings are specially designed for high definition. According to the model, function, and design of the lens, there will be a number of different kinds of glass in different combinations in one lens, with everything designed to work as a unit. For example, one glass could meet a very high specification in one area, but in another area it's somewhat lacking. The next element put in line will actually correct for the previous elements' problems. In order to reduce chromatic aberrations while increasing the resolution of the product, HD lens manufacturers have tightened mechanical specifications.
Chromatic aberration is very much like errors in color printing: when the registration is off you get blurs and distortion. In video, the three different colors used--generally referred to as "RGB" (red, green and blue)--do not always get through the lens equally (size/frequency, etc.) and that causes blurring. MTF (modulation transfer function), which is a way of expressing reproduction of contrast, happens out toward the edges of the picture, because the colors are not all focusing the same. For instance, all three colors on an edge, out in a corner, may have to overlap each other, and if the red is a thicker line (because it's not quite as focused as the others), fringing occurs.
For digital cameras in general, and HD cameras in particular, lens manufacturing has become even more precise (and more difficult) than ever, because the three CCD "chip" cameras do not allow adjustments to be made in the camera to compensate for any error in the lens. With the old tube cameras an operator could compensate for a registration problem. Now, if the chips are not exactly the same and correctly aligned, you still have a registration problem but no means of correction in the camera. For HD lenses, which must be excruciatingly precise, the manufacturers tried numerous approaches to create correction elements within the lens. Manufacturers are now using super electron beam coating for beam-splitting prisms, which has greatly benefited resolution.
While the glass is being ground and coated, another part of the factory is manufacturing the cams, the focusing sections, and all of the mechanical parts that are necessary inside the lens. These parts are also specifically designed for HD and, again, the specifications are very exact, more than would be necessary for an SDTV lens. When all the parts are made, including the optical parts, they all meet at the assembly line, and the lens-in-the-making goes through many people doing many different jobs and testing many times. And when the last person puts in the last screw and tightens it down, the lens then goes through total quality control testing as a whole system. There could be 20 different elements or more in one of these lenses, all working in conjunction with each other. In the end, the lens has been designed as a system that can provide the finest picture possible.
Lines, Formats and Resolutions
Canon and Fujinon report their HD lenses will work for both interlaced (i) and progressive (p) scan. The HD lenses being manufactured today will not perform properly on a 1080p system; they will, however, perform on 480p, 720p or 1080i standards. Performing on those lower TV-line formats may be a moot point, according to some sources. Today's HDTV lenses may represent the best quality lenses in the market, but differences in format resolutions may not allow the drastic differences in picture quality you might expect. Comparisons between standards will also be difficult, as results may vary due to camera equipment and formats.
Other lens experts assert that as far as the HD lens is concerned, the format of the camera--whether it's 720p or 480p or 1080i or even 1080p--makes no difference. Format is a camera issue; it's not a lens issue. An HDTV lens has to do with the overall quality of the picture that is transferred to the camera. Once the picture is in the camera, whatever the camera does with it from that point on no longer concerns the lens. The size of the CCD, and the placement of that CCD matters, but what the camera does with the video is essentially the camera's business. According to these experts, if the lens exceeds the system resolution-wise, a shooter is at least guaranteeing the maximum out of that camera system. Some shooters do use HD lenses on SDTV cameras. Reasons vary: some may be trying out the HD lens now so that when they buy an HD camera, they'll already have the lens and be familiar with its uses; other might be trying to squeak every last bit of resolution out of their current cameras.
16:9/4:3 Switchable Cameras
High definition means shooting in a 16:9 aspect ratio, but 16:9 does not mean high definition. The 16:9 aspect ratio is not what distinguishes an HD lens from an SDTV lens; in fact, there are plenty of true 16:9 SDTV lenses available. Instead, the quality of the picture is what truly separates HD lenses from SDTV lenses.
A number of camera manufacturers are touting 16:9/4:3 switchable cameras. These are NTSC 525 TV-line digital cameras equipped with what's called alternately a "minimizer," a "ratio converter," a "retro-zoom," or a "crossover." It's a unit of glass that compensates for the 20 percent angle-of-view lost when you switch from 16:9 to 4:3. On these cameras, when you go to 4:3 you lose wide-angle, and this (0.8mm) wide-angle converter--built into the lens and switchable through a toggle switch on the camera--will give you back what is lost in the camera; to the eye, it will look like you never lost anything.
You can shoot 16:9 on these cameras with any current SDTV lenses. However, when you go back to 4:3, your lens becomes 20 percent more telephoto, and this is true of every camera manufacturer, with the exception of Philips. Most camera manufacturers reduce the chip; the chip starts out as a 16:9 chip, and the edges (sides) are pulled in to make 4:3. The Philips system starts out with a 4:3 chip, and reduces vertically to 16:9 so the angle-of-view is not lost.
Using an HD lens on a 16:9/4:3 switchable camera will not give you high definition. It will give you the best possible picture that a 525-line digital camera could do in 16:9, but switching to 4:3 would result in the same problem that an SDTV lens would have. Without the 0.8 wide converter in the lens, your viewing angle would change. This is a function of the camera system, not the lens; however, Canon now offers HD lenses which can be equipped with the 0.8mm wide-angle converter in the lens.
The two leading manufacturers of broadcast and ENG lenses are, not surprisingly, the leading high definition lens developers, manufacturers, and suppliers. For the last several years Canon has been doing research and development into the high definition lenses used by Sony, Philips and a few other companies. Those lenses were very specialized and almost hand-made, and the price reflected it. A powerful HD telephoto zoom, with a 40X magnification ratio, had a list price of almost a quarter of a million dollars.
The introduction by Sony and Ikegami, among other camera manufacturers, of a standardized 2/3-inch lens-to-camera interface for HD, also called the B4 interface (a standard interface that already existed in the current SDTV cameras and lenses), made the development of more economical lenses possible.
Focal lengths and specs sound familiar on HD lenses, because lens manufacturers designed HD lenses to be as close as possible to SDTV lenses, to make the transition to high definition easier for camera people. The HD lenses are designed to look, feel and operate like the SDTV lenses that shooters currently use, with only some slight differences in focal length. Initially, HD zoom lenses are expected to be the most popular, but fixed focal length HD lenses will become necessary as more film-style work, such as commercials and TV series, will be shot in high definition video.
By Randall Paris Dark
'Twas the night before Christmas and all through the house, not a creature was stirring except for the FCC.
On that fateful night, the visual electronic and computer world would be changed forever.
The future not only became brighter, it became a lot wider as well.
Tuesday, December 24, 1996, the Federal regulators approved digital television standards that will deliver movie-quality television to America's living rooms. The Federal Communications Commission has given television stations the go ahead to deliver incredible digital signals, sharper pictures and up to six-channel CD-quality sound in many different formats. These formats include an aspect ratio of 4:3 and 16:9 as well as high definition TV with an aspect ratio of 16:9. During all this, the broadcaster must also continue to transmit analog TV that has an aspect ratio of 4:3. Confused? Stay tuned. The following formats listed below are production and transmission formats and are not necessarily display formats (in pixels):
These formats are known as the 18 "ATSC Table 3" formats (see Glossary). Each frame rate has a 1000/1001 frequency change to accommodate NTSC color (24=23.98, 30=29.97, 60=59.94), for a total of 36 formats.
Whether you believe HDTV or DTV is coming, going or staying where it is, the bottom line is that the future is Electronic Widescreen High Resolution TV/Computer/Movie Theater. Period. That is evolutionary, not revolutionary. As a species, we have evolved from primitive finger painted drawings in our caves to primitive low resolution moving images (television) in our homes and we will not stop there. Humankind has always wanted bigger, brighter, sharper. (How else can you explain the clothing styles of the 1970's?) This change will affect every one of us, but initially it will have the biggest impact on the broadcasters. And you don't have to take my word for it. The government has told the broadcasters they have to switch from analog to digital television. The clock is ticking.
HDTV is not television as we know it, it is not an NTSC camera shooting in 4:3, low resolution information, nor is it a 2:1 film camera. High definition is another animal, another tool. To say one is better or worse than the other is like saying a Picasso is better than a Henry Moore. It is just different. It has the advantages of film in that it has the wideness in shape and the ability to show incredible contrast and detail. It also has an advantage over NTSC, not only because of the improved resolution, but because you can do something more than the continual 4:3 TV close up when framing shots. Finally, the creatives can frame a much more interesting shot, off centered and allow a shot to be loose enough to give a sense of place.
HDTV/DTV conversion, or at least a statistically-significant, financially-viable deployment of the technology, is the largest marketing challenge in the history of consumer electronics--and whatever happens, it will rock the very economic foundation of the broadcasting industry as we know it today. Unfortunately, HDTV, ATV and now DTV have been regarded as a science project by industry executives. Only now are we beginning to see these broadcast executives react to the business-model issues of HDTV/DTV.
Regarding that business model, one of the key issues surrounding it is the idea of producing in a higher-resolution widescreen (16:9) format and downconverting the center (4:3) section of that image to NTSC in order to provide the feed for the existing (revenue-generating) NTSC channel. I have been producing HDTV since 1986, and for various creative reasons, it is likely that this process will limit the quality of programming in both formats. Again, this issue has been regarded as part of a science project: scalability, interlace-verses-progressive scan, quality of vertical filtering, downconversion, pan-and-scan, etc. But the real issue is: Can you produce compelling programs that are tailored to the strengths and weaknesses of each format through the use of this process? I believe the answer to this question is no.
That being the case, the slow adoption rate of DTV predicted by the consumer electronics industry means two things: First, that the integrity of your NTSC programming must be retained to protect your position in the NTSC marketplace, your primary source of revenue for the next 10 to 20 years, and; second, you must provide high-quality widescreen HDTV programming tailored to the format so that consumers actually perceive a quality difference when evaluating their purchases. In essence, this means that in most cases, you must produce the two streams separately.
Take the case of local news. The most obvious problem here is creation of cross-standard graphics elements. While each station generally invents its own style for presenting these graphics, it is unlikely that a design that works in 4:3 will be optimum when presented in 16:9, and if 16:9-optimized graphics are converted to NTSC-cropped-4:3, any information in the side panels will be lost. And this doesn't even touch on the graphics composition issues created by the wider viewing angle, bigger screen size and closer viewing distance, which are the main differences between true HDTV and widescreen NTSC/SDTV. Much has been said about upconverting the existing news programs in the HDTV world, but once the viewer watches one station's news in HDTV, will they watch the competing station in upconverted NTSC?
Framing for Sports or How I learned to Pan and Scan Live
Over the past 10 years, I have noticed that the aspect ratio of HDTV fits perfectly with many sports. The shape of the playing fields of football, basketball, hockey, and soccer to name a few, is rectangular in design. When soccer is shot in HDTV, you can see more of the field and watch how the team positions itself to attack the opposition. In football you can see both the defensive back and the offensive back in the same shot without having to be completely wide. Not only is the shape of HDTV almost the same as a skating rink, but with HDTV the viewer may finally find the puck in hockey. These sports are a natural for the 16:9 aspect ratio, but there are problems that come with the crossover that will happen during the transition period.
Imagine a basketball game shot in HDTV and downconverted live, edge cropped, because no viewer, let alone no network, would allow letterbox sporting events. There is also a limited amount of space for cameras, so many events will not have the luxury of both HD and NTSC cameras and crews. Therefore, simulcasting using the HDTV equipment as source equipment will be the order of the day. In that scenario, where would the director put the net in the frame? Safe action for NTSC leaves the net almost in the middle of the 16:9 frame. Put the net in the edge of the 16:9 frame and it doesn't even appear in the NTSC feed. Live pan and scan seems to be the immediate compromise. This means that there is a new operator in the mobile. His sole job would be to pan with the action, making sure that the framing of the shot remains in the safe action area at all times, giving the best possible framing in both worlds. Difficult but do-able.
However, with every advantage there are also limitations. Think tennis. The primary camera position is behind the tennis player, where the 4:3 frame works perfectly. The 16:9 frame fights that angle, there is too much air on each side of the court from that camera position. Pan and scan from the end camera would be next to impossible. With a few sports, new camera positions will have to be experimented with and we will have to find new and compelling ways of covering certain sporting events.
Editing for Two Worlds
There are many subtle editing issues as we evolve into this new and complex world. Take the case of a comedy program (sitcom) where the editing sets the pace of the show and in large measure determines the comedic timing of a performance. Say you want to edit just after someone enters the shot. Does the edit occur just after the actor enters the 16:9 frame or the 4:3 frame? Which do you compromise? If you edit separately, will the lengths of the scenes be different? Framing and composition for the same show possess new and interesting problems. Picture, if you will, a head to toe shot in 16:9. There is an immediate feel and look to that framing. Now picture the same shot in 4:3. The look completely changes. No editing can change that problem.
Picture a close-up two-shot in 16:9. In NTSC that shot is either a shot that has each face half off the picture or you need to pan and scan the shot in post much like you do when you do film transfers for television release. In a sitcom with bang-bang timing, this would bring new meaning to the words whip pan.
Simulcasted edge--cropped camera moves present an interesting scenario. Pan an actor into the 16:9 frame. As he enters the picture, he starts to talk, while in the 4:3 frame we hear a mysterious voice with no one in the shot. If he waits until he enters the 4:3 frame to speak, the 16:9 audience will think he has forgotten his lines. Zooming in and out would further complicate this already dizzying scenario. Depending on what aspect ratio your television is, the actor may or may not be in the shot at different times during the zoom. Again, what works for one ratio may not work at all in the other.
One possible solution to these problems would be to convert from HDTV (or a lower-resolution 16:9 format) to NTSC using the "letterbox" method. This puts black bars above and below the 16:9 image, or places a single large bar above or below the image. Although this unused area could contain program-related graphics material, experience has shown that the U.S. market is reluctant to accept the smaller images that letterbox provides on a given size display.
For many programs, the network broadcasters and their TV-station partners must maintain two completely separate program streams during the conversion period when legacy-hardware consumers must be protected, or they will have to compromise the creative integrity of the 16:9 program, hardly creating a compelling case for the purchase of new television receivers.
It is not only an issue of who will pay for the transmitters, antennas, towers and distribution infrastructure, but who will pay for the creation of the separate programs, particularly in the early days (the first 10 to 20 years) when the penetration of DTV is projected to be quite limited.
Can There Be Compromises?
A Real World Example: Woodstock '94
There seems to be a common fear in the pay-per-view world that viewers will demand their money back on the grounds of "technical problems" if they see black bands because of letterboxing. This usually leads to a decision to air the live event in "edge crop" where the sides of the wide screen image are discarded in the conversion process. Of course, the high definition users are then concerned that the director will focus his attention on the 4:3 area and not use the widescreen (16:9) advantage. That usually leads to concerns over how the person switching the selectable ISO will cover the event for post production.
A settlement was negotiated that not only quieted the concerns, but allowed the pay-per-view broadcasters to test the market in non-prime time and gave the viewers a way of identifying live and delayed broadcasts. The live broadcasts were converted in a compromise 14:9 aspect ratio which allowed the under scan on most receivers to cover the black border on the top and bottom. The backup converters ran in letterbox mode and the NTSC D2 recordings for Woodstock Overnight were made from these signals. The Overnight replays were made over a stylized background which made the top and bottom area seem to be part of the program, much the same as the sports ticker on CNN Headline News. So the widescreen format was converted from a drawback to an advantage. The promoters seemed happy with this approach, and even agreed not to complain if we had to switch to the letterbox mode in the live broadcast because of equipment failure.
The conventional NTSC mobile unit provided all the available bells and whistles for packaging the program, including digital effects, still store and live graphics. All transmission was standard NTSC and was no way affected by the high definition production. The high definition production was broadcast at a later date in Japan1.
Over the next 10 to 15 years, the creative and technical community will be forced to deal with having to simultaneously transmit the same program using two TV channels, one for programs in the existing analog format and the other in any or all of the new digital formats. There are many difficult issues to be worked out during this period. Some programs will make this transition seamlessly, others will be compromised. But is it impossible to do? No. Simulcasting has a future and upconverting has a limited future. What the real challenge is and what will be truly exciting are the new possibilities--having to re-think existing programs and develop new types of programs. Programs that are best suited to this new format. HDTV and widescreen are enhancing technologies. We are in its infancy, only just beginning to look at the possibilities. Having recently watched a few hours of old black and white television programs, it is easy to see that over the past 30 years we've come a long way. With this exciting new development in Electronic Widescreen High Resolution TV/Computer (television), it is apparent that we still have much to learn--and learn it we must. There is no going back.
By Jeff Alred
I was approached to demo a high definition camcorder at the ESPN Summer
X Games in San Diego, California in 1998. Gladly I accepted the offer; finally I could use the "format of the future" I only read about in college some years ago. My experience as an ENG photographer leaves me with limited digital exposure, so as you can imagine the HD format presented many new challenges. Two of the biggest challenges I ran into while using this format were the aspect ratio and clearer resolution.
The HDCAM acted much like a Sony 600 or 700, only the viewfinder showed a 16:9 aspect ratio. I picked up the camera and started shooting without too much guidance. I actually passed the camera off to show many different handheld camera operators, and they used the HD camcorder almost instantly. White balance, audio settings and other manual functions were in the same location, so most of my attention could be focused on shooting with a letterbox look instead of the 4:3 aspect ratio I was so used to.
Once I began shooting with the camera, I found myself trying to maximize the whole frame, especially with the extra thirds the format presented to me. Since my proportions were different with this format, I was looking at the "fringes" of the frame rather than the subject I was interviewing. As I overcame the initial newness of the format, I began to utilize the frame to my advantage. I started to use right or left justification of my subject so the editor could use the other two-thirds of the frame for effect or B-roll. I framed shots with specific items in one-third of the frame and the subject sharing the remainder of the frame. This aspect ratio allows the photographer to marry together one or two products with the subject, something that 4:3 just doesn't allow you to do.
When shooting action, it took some getting used to the skinnier, longer frame. At first, I began tilting up and down too slowly, realizing the action was going through my frame twice as fast as I was used to. I really enjoyed having a longer frame, especially for the speed shots where I could let the athletes enter and exit through the whole frame. It was a good method to relate the speed to the fan sitting at home.
The second major challenge was the clearer resolution presented through the improved scan rate. I was really impressed with the crispness of the picture--even subtle details were clear. We set up an interview where we had to make sure not even a gum wrapper laid on the ground in fear of it being seen by the camera!
When we returned to the edit room to screen the footage, I was amazed every time with how the format translated an image compared to how it looked in person. Most of our interviews were done on location, but this format may cause some headaches for set designers or lighting directors. It really exposes any flaws or patches in set work.
Since this is such a clear and concise image, some shots could tell stories without words. Shots of faces which show the wrinkles of experience, the ripples of muscles during competition--I used them all because the format's resolution is almost truer than life. I also utilized the shutter with this format, and it gave me an image that was almost unexplainable. I thought the format was already impressive, but this function could capture every frame even more crisp than before. I began shooting the majority of my video with shutter, and the reaction from the edit area was equally enthusiastic.
This HD camcorder is very easy to operate. The aspect ratio definitely kept me on my toes, but I found many positive ways to use this format to my advantage once I became comfortable with it. With the clearer resolution and 16:9 aspect ratio, this format will be a favorite of sports producers, because it gives the viewer a fan's perspective, the peripheral vision that has never been previously offered.
By Michael Silbergleid
The one good thing that analog and NTSC did for broadcasters and videographers was to hide a multitude of sins. Here's a simple example: If you shoot a black and white glossy photograph, a monitor will show you sharp, highlighted edging. This edging has high frequencies that the camera and monitor can see. But a tape format like VHS doesn't see them at all. So instead of the picture looking as bad as it did on the live monitor, it looks "better" from tape. All the high frequency noise was removed by simply recording on a narrow bandwidth analog tape format. Record that same image in digital (and especially high definition digital), and you'll get all that high frequency "noise" and a worse-looking image.
Another NTSC savior: 30 frames per second interlace. Look at a still frame (not a field) of video with motion not shot using a fast electronic shutter, and you'll see that the object moving is blurry. Even when that object is at rest, the image is not perfect. What this means is, for the most part, that there is not a great difference between the sharpness of the two images. (See figure 1.)
Now do the same test with high definition. What you'll see is a very sharp picture of the object at rest, but blur when it moves. That blur is called motion blur. You can eliminate motion blur by using a high speed electronic shutter, but the video then takes on a strobe-like effect.
Here's a real-world example: During a demonstration of HDTV, blur was noticed in the image. At first it was thought that the focus was slightly off on a scene of a woman walking down a street towards the camera. Although tight focus on the extra-sharp high definition image will be critical, it was not the problem in this case--motion blur was. As the woman moved up and down in step, her image blurred. This blur would not normally be noticeable in NTSC, but in high definition it was.
It was noted that the scene was shot in interlace and we were also watching an interlace image. When the image was shown in progressive, about one-half of the motion blur was removed. But because of the interlace production and shutter speed of 1/60th of a second, the blur was still noticeable.
By now, we all know that we can no longer use fake props and set pieces or an old- looking studio set with HDTV as the clarity gives away all our tricks and illusions.
Older NTSC sets shot in high definition do not hold up well under the sharp scrutiny of the high definition camera. The sets look cheap. Graffiti on the sets "reads" for the first time and backgrounds begin to look awful. Immediately it was realized that new sets would be needed for high definition production, and traditional NTSC set "tricks" would no longer work. Those "tricks" include fake bookcases with painted-in books, slightly off paint jobs on walls, and other things that producers and designers knew would not be reproduced when going through NTSC.
Simulation of motion blur in a high definition image. On the left an image shot without helicopter movement in the frame (could also be with movement in the frame but with a high speed electronic shutter). On the right, a simulation of the same image and quality with movement in the frame and no electronic shutter. Motion blur can make high definition look soft.
You may be shooting for today, but you want to protect for tomorrow's high definition widescreen world.
Today, many productions are shot in 16:9, posted in 16:9 and then center sliced with an aspect ratio converter for the final 4:3 air master. On screen composition is for the 4:3 image, while protecting the 16:9 image.
Keep in mind that shots composed for a 16:9 aspect ratio may look awkward in 4:3 and that if you adjust camera detail for monitoring on an HD monitor, your NTSC picture may look soft. There are always going to be compromises to be made in the world of widescreen and high definition.
A widescreen 16:9 television does not guarantee the premanant exile of letterbox. 16:9 has an aspect ratio of 1.77:1, but a number of motion pictures are produced in an aspect ratio of 2.35:1. To accomodate this wider-than-16:9 image, the motion picture is presented in a letterbox format.
To avoid what many consider to be the annoying black bars of letterbox, Home Box Office has decided to pan-and-scan all newer 2.35 film to high definition transfers to fit within the 1.77 aspect ratio of their HBO HD service. This means approximately 26 percent of the image of a 2.35 motion picture will be lost at any one time. While purists demand that films be shown in their intended aspect ratio, others (like HBO) believe in filling up the screen.
An interesting exercise is to take a DVD that has both a 4:3 pan-and-scan on one side and a 16:9 letterbox on the other (several films, including Austin Powers: International Man of Mystery, have been released with this feature). Watch a scene in one format then the other and see if you find what is missing in 4:3 or visible in 16:9 to be of major importance.
14:9: The Great Widescreen Compromise
As you've seen before, 14:9 might answer many of the problems of 4:3 versus 16:9. At the International Broadcasting Convention held in Amsterdam, Holland, The Netherlands in 1996, a paper called "The Simultaneous Transmission Of Widescreen And 4:3 Programmes" by M. L. Bell and H. M. Price was presented. Within this paper was the first major look at the 14:9 compromise, as made by the BBC.
Let's start with production and end with distribution: Our old programs (and our current ones) are 4:3. Our new programs will increasingly be 16:9. We can protect for 4:3, or pan-and-scan for 4:3, or do true 16:9 and letterbox for 4:3.
The BBC had that problem: Simultaneous transmission of widescreen and 4:3.
The BBC and all the U.S. networks know that most viewers dislike letterbox. So how do you show 16:9 on a 4:3?
Their answer--14:9 "half-letterbox." There is minor letterboxing and some minor loss of the edges of 16:9, but the BBC found that most viewers were okay with this format.
Now, how do you present 4:3 material on a widescreen 16:9 television set?
As bad as it sounds, and the BBC admits that there are no easy solutions, it is with side curtains. The picture could be expanded slightly to reduce the curtains, but at the expense of the top and bottom of the frame being cropped.
In the years to come, experimentation will help to further answer these 16:9 and 4:3 questions.
Compression is used to make digital video affordable. And the type of compression we use literally throws bits of data away based on how humans visually perceive information. Look at how a format (and its compression scheme) performs under different conditions (lighting, camera movement, subject movement, color saturation, etc.) and judge for yourself.
There are only two issues that can cause you grief with regard to production and compression: overloading your encoder and concatenation.
All of the encoders that you'll be using are realtime encoders. They must compress your video data at a steady rate regardless of the images you shoot. Problems arise when the visual information is too complex for the encoder to handle. All encoders react differently to the data they are given based on the type of encoding (DV, MPEG, M-JPEG) and the compression ratio they must work at.
A scene too complex for an encoder might be one with a quick pan, zoom or dolly. Or one that has lots of motion in it where the image changes dramatically from pixel to pixel and from frame to frame. When an encoder "chokes," two things can happen. It can either freeze up and re-output the last frame of properly encoded video again or it can produce macroblocks--a compression artifact--making a large block of pixels look all the same (color and brightness). (See figure 2.)
Decoders can also "choke" since they need to work in realtime as well, and suffer from the same symptoms.
Practice with your encoder (your camcorder or deck) will let you see what it is really capable of handling...and most importantly, what it is not capable of handling and what you must avoid.
Concatenation is the other problem--when you use different types of compression on the same piece of video (DV and then MPEG, for example). Each compression scheme handles data differently, so compression artifacts (known as macroblocks because they look like blocks in the picture) and loss of video resolution are more apparent. Even staying within the same type of compression can cause problems, as the same brand and model of encoder may encode the same signal in a different manner.
While concatenation may not show up until generations later (if at all), you might want to know what compression will be used in post production as well as in the duplication master and distribution copies. Limiting the times the video gets re-compressed and the number of different types of compression that the video will be subjected to will only benefit you in the end.
figure 2. Macroblock encoder errors.
How Different Production Formats Can Be Used
While people, stations, facilities and networks begin to position themselves with their production format or formats of choice, there is some agreement as to how these formats will be used.
Film will continue to be used as the ultimate high definition imaging format. Currently, more than 80 percent of primetime programming (not including news programs) is shot in film. Telecines can output the film image in any number of formats or even as a data file.
While looking at the information below, keep in mind what each format offers as well as the complexities of each type of production. You'll soon realize that all of these are natural fits. Also, the 704x480 format stretches pixels either horizontally for 16:9 or vertically for 4:3, so most people feel that it won't see that much use. It should be noted that equipment is just being introduced for many of these formats, such as the 1080p/24 video format introduced in 1999.
Movies (produced at 24 frames per second)
Sports (fast action)
High Definition Episodic (big beautiful pictures)
Regular Episodic (average television)
A Universal Standard: The CIF
The world now has a Common Image Format (CIF) to allow producers the world over to trade and distribute content. Ratified by the International Telecommunications Union (ITU) in June 1999, the 1920x1080 digital sampling structure is a world format. All supporting technical parameters relating to scanning, colorimetry, transfer characteristics, etc., are the same worldwide. The CIF can be used with a variety of picture capture rates: 60p, 50p, 30p, 25p, 24p, as well as 60i and 50i. The standard is identified as ITU-R BT 709-3.
Producing in digital, and especially widescreen, comes with its own set of problems and concerns. The same way you have honed your craft as an analog and 4:3 professional, is how you will strive in the digital world--through practice. You've spent your career watching the work of others and critiquing your own work to become better at your craft. In the digital age, this skill may be your most valuable.
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