R & B Communications, Inc. Cleveland, Ohio 440 946-9511
A High Definition Primer High definition production has become the standard broadcast signal since we switched from analog to digital broadcast television. However, HD is often an improperly understood format, which is why we decided to provide this outline of what it is and how it works. If you have ever seen a movie or television show in wide screen, then the look of HD is not unfamiliar to you. The methodology behind it however, may be completely alien.
High Definition Versus Standard Definition The most outwardly visible difference between the two formats are their aspect ratios, a term that refers to the mathematical expression of a frame's width divided by its height. So- called "standard definition" video, (or NTSC video - the proper term for analog television) is represented by a 4:3 aspect ratio. HD has a 16:9 ratio or wide-screen image. And of course, when viewed on a quality HD television, high definition has an image that is four times sharper than a standard definition image due to it's higher resolution. Good quality high definition images on a large screen can look stunning.
Why It Looks The Way It Looks The highest resolution or picture quality in HD provides 1920×1080 progressively scanned images. 1920×1080 refers to the lines of pixels in a frame (NTSC is 720×480 pixels). Progressive scan means that these lines of pixels are being displayed in an ordered full frame sequence to make up each frame of video. There are thirty frames that make up one second of video in either HD or NTSC. 1080P is only used in Blue Ray and is not broadcast. 1080i and 720P are the current HD broadcast standards in the U.S.
Progressive Versus Interlace Scanning Virtually every new flat panel video display today is progressive. LCD, DLP, LED and plasma screens for both television and computers are progressively scanned. When television was first invented however, interlace scanning was necessary because the cathode ray tube or CRT monitor could not produce a full screen of video thirty times every second. The phosphors in the CRT would lose their "glow" too quickly and thus create a lagging and uneven brightness in the picture. The tube could not draw the image from the left to the right in a progressive mode fast enough to keep the image on the entire screen to produce a smooth, full motion television signal. The fix at the time was to create two fields of half the total resolution each. Each field made up one frame of video or, when combined, one whole picture. Each field had 262.5 lines for NTSC and worked in an odd and even mode. The cathode ray tube would draw the odd field first, starting at the upper left with lines 1,3, 5, 7 etc, then scan the even lines 2, 4, 6, 8 etc. Persistence of vision helped make this TV trick work just as it does with film. Two fields for every one frame, 60 fields a second or restated as 30 frames per second, tricks the eye into smooth motion. With the advent of better CRT materials and eventually, with the introduction of LCD, DLP, plasma and now LED technologies, progressively scanned video is now available. The progressive images are smoother, resolution is greater and all without various artifacts associated with interlaced images.
720P Versus 1080i Both high definition 720P and 1080i images have advantages and disadvantages but both produce very high quality pictures. Some think of 1080i as having higher resolution than 720P, but the reality is that the vertical resolution of a 1080i image is 540 lines per field. By doubling the fields each second, 540 lines become 1080 lines when combined or interlaced, hence the "i" in 1080i. The advantage of 1080i is higher perceived resolution. Meanwhile, 720P offers a more efficient broadcast signal. All 720P frame rates are progressively scanned making for a smaller bandwidth when used in broadcast applications. 1080 however is available in both progressive or interlace, the latter 60i signal is used in broadcast applications. 1080P is only used in movies recorded on Blue Ray discs. Some networks are beginning to offer movies broadcast in 1080P as well. Broadcast networks use both 1080i and 720P for different reasons. NBC, CBS, PBS use 1080i for its high resolution while ABC, Fox, ESPN use 720p for its signal efficiency. One signal type is not necessarily better than the other. Both produce very high quality images, just in different ways.
HD Formats Versus Frame Rates When it comes to HD standards, keep in mind there is no standard. When discussing network and cable channel television, there are two high definition resolutions that are currently broadcast, 720P (the P stands for progressive scan) and 1080i (the i stands for interlace scan). Within those resolutions, there are multiple frame rates. Even if a network broadcasts at 1080i, video acquisition can still be made at 1080/24p or 30p. The reason to shoot with a 24p frame rate is for a more ‘film like’ look. The motion captured is similar to how a film camera captures images – one full frame at a time, 24 or 30 frames per second. However, in video, fast pans and quick motion may have a stuttering effect. Motion will not looks as smooth as captured at 60i (60 interlaced fields or 30 frames per second). This is true for 720/24P or 1080/24P. 30P is a little smoother but does not look as much like film as video shot at 24P. Each project type and production style will dictate the field acquisition format, no matter what the mastering format requirement is.
HD and the Web More and more, the internet is readying itself for HD content. Video streaming sites like You Tube, Netflix, Hulu, Amazon Prime, Vimeo and others are starting to broadcast channels capable of handling the HD codecs (compression/decompression process) needed to play video in real time without buffering. High definition content with its greater amount of information, makes it difficult to download and view the larger files that HD creates. Very quickly, the speed of the Internet will catch up and the compression technology used in creating files will improve in order to broadcast true HD signals on the web. As of now, broadcast and cable television are higher quality means of content delivery
A Note of Caution Recording in high definition does not necessarily mean you will always produce better quality video images. Now that the HD format is widely available to the public, consumer cameras are being released with ever lower price tags. However, cheaper cameras do not always deliver the stunning image you might expect. If you view a high definition broadcast signal on a good quality television, you will quickly see that there is a big difference in HD images regarding quality. Lower quality high definition can be as bad as viewing a standard definition signal. How can that be?
Prosumer Versus Broadcast HD Cameras Some programs are shot with lower quality “prosumer HD” cameras. A prosumer ("professional consumer" hybrid) camera will not deliver the same quality image that an expensive broadcast camera will. These prosumer cameras, while more than ideal for recording personal events and home video use, do not compare in quality and functionality to professional or broadcast grade equipment. This is a good example of you get what you pay for.
One of the first compromises in prosumer cameras is their ability to reproduce a true high definition signal. Most prosumer cameras record less information or a highly compressed HD signal. Professional cameras record high definition at higher bit rates for the best quality resolution.
Many prosumer HD cameras do not have the option to change lenses, something that can greatly effect the quality of a production. The ability to use different lenses specifically designed for HD production will provide sharper images with more detail and better resolution. Broadcast HD lenses usually cost more than an entire prosumer HD camera with a fixed lens. Such is the quality of their optics.
Something else non-professional HD cameras lack is exposure latitude, meaning they do not capture and handle contrast as well as their professional counterparts. Correct exposure and the ability to handle highlights and contrast is essential to reproducing high quality video images. Color reproduction can also be effected by using a prosumer type camera. Professional cameras have larger and higher quality image sensors that provide much more accurate color reproduction. In addition, broadcast cameras have the ability to modify or adjust the look of the image in a menu function much more readily than a prosumer camera. These adjustments can fine tune the image to provide stunning, life-like results.
Before choosing any video format, call us to help determine what might be best suited for your individual production. We carry a variety of cameras for every budget. For more information about high definition, visit our HD vs. SD link.
Qualities of a ‘Film Look’ Many times productions strive for a film look as opposed to the regulae broadcast news/sports look that video cameras typically produce. Achieving the qualities of a film look involves several factors.
First is the choice of camera. Today, many manufacturers offer cinematic digital cameras. These type of cameras differ from ENG (electronic news-gathering) type cameras in several ways. Digital cinematic cameras usually have a large "full-frame" sensor similar to that of digital single lens reflex (DSLR) cameras. One large sensor, usually the size of a frame of 35mm film, helps produce a film-like image rather than an ENG video camera's electronic image. This large sensor along with cinematic type lenses, allows for control over a narrow depth of field or the amount that is either in or out of focus in a given frame. This effect is similar to the way an actual film camera controls focus. The digital camera can also be set to record 24 frames per second which is similar to the way a film camera shoots. By making adjustments to the camera’s gamma settings and reducing a bit of electronic detail, a digital camera can easily emulate film today.
Additional methods can be employed to make productions even more "film-like". When shooting film, there are usually little to no zoom shots. The eye does not zoom and it can look unnatural. Instead, the camera is physically moved in or out, dollied back and forth, or craned up and down to provide movement. The use of dollies, jibs, or a Steadicam unit allow the camera to be moved in predictable ways and enhance a film look.
Other methods of producing a film look include large source key lighting and cinematic blocking between camera and talent. In post production, the use of cuts as opposed to dissolves or effected transitions add to the film look. And of course, the wide screen aspect ratio of high definition enhance the feeling of film. All these factors contribute to help make the look of film when shot digitally.
Please call us if your production requires a high-end film look. We have the right tools and talent to get the job done.