The "more" and the "less" in selecting a lens today

The most common method of selecting a video package is to first determine which camera is the most convenient for the work you want to do within the available budget. Superficially seen, this reasoning seems legitimate; however, the lens is often forgotten and this can be a major mistake.

Lenses for normal ENG/EFP cameras generally fall into one of three categories. The first consists of the built-in lenses. These lenses come packaged with the camera and, as a result, are very cheap. They are usually designed simply to be good enough to survive. At best, the optical quality is minimal and the mechanical aspects of the lens are such that they will not be able to perform properly for a long period of time. These lenses are an option only for the use of beginners or in situations where the camera and lens are disposable.

The next level is made up of professional quality lenses that constitute a step beyond the lenses incorporated into the camera. These lenses offer superior optical quality and greater mechanical strength, and perform quite well in much of the application, under moderate shooting conditions of course. Unlike built-in lenses, professional-quality lenses are available in various zoom ratios and different focal lengths. There are wide-angle and telephoto lenses, as well as lenses with built-in 2X extenders. In addition to the wide variety of options, there are many accessory products such as telephoto and wide-angle converters, studio zooms and focus controls. Professional-quality lenses are designed for mid-price cameras and, if proper care is taken, will provide many years of good service.

Lenses for open transmission, or broadcast lenses are at the top, both in terms of optical quality and mechanical strength. These lenses are designed with the aim of reinforcing the performance of the best cameras and offering many years of reliable service under the most difficult situations. Broadcast lenses are used by newscasts and production teams on a global scale in almost every type of production. Although it is not a recommended practice, these lenses have remained in use for many years without any maintenance. New generations of broadcast lenses offer digital services such as faster and more accurate zoom, and other digital features such as Quick Zoom, Cruise Zoom, One Shot Preset and RS-232 interface for remote zoom, focus and iris control. If your livelihood depends on your equipment, broadcast lenses are your only option.

Currently, camera manufacturers are offering dual format products. These cameras allow the operator to choose between the old screen ratio standard (4:3) and the new widescreen standard (16:9). One fact, which is sometimes overlooked on most of these dual-format cameras, is the loss in perspective angle when in 4:3 mode, compared to a regular 4:3 camera. The result is an image that is about 20% narrower than what would normally be expected. To explain in more detail, a lens with an 8mm focal length on a normal 4:3 camera will exhibit an effective focal length of 9.6mm on the dual-format camera, while operating in 4:3 mode. This can become a serious problem if you are used to shooting from the open side of the zoom. To correct this, there are lenses with built-in ratio converters. These converters are built into the lens and can be switched from one mode to the other, as many times as needed. This type of dual lens corrects the 20% difference in perspective angle and gives the operator the same shot you'd expect on a normal camera. The lenses with the built-in ratio converter are available in both professional and broadcast formats.

Technology, both studio and field lenses, has progressed steadily in recent years. Studio lenses have become wider and field lenses faster. Current studio lenses offer focal lengths from 7mm to 168mm, while field lenses have transformed from the standard 55X to a staggering 87X with focal lengths exceeding 2200mm.

The studio lenses are designed for close-up work with a minimum object distance of less than three feet. The typical operating distance in a normal news production scheme is 6 to 10 feet. Since it is necessary for the presenter to read the teleprompter, any operating distance is usually prohibitive.

Field lenses are typically used for sporting events and for wide-scene productions where the camera is usually placed at a great distance from the action. The minimum object distance of these lenses is typically 6 to 10 feet, making them completely unsuitable for normal study applications.

Like ENG/EFP cameras, studio and field cameras are available in an interchangeable format between 4:3 and 16:9. They also exhibit the same 20% loss in perspective angle as with smaller ENG/EFP cameras. This loss is not as critical in the case of field cameras because most shots are recorded with the telephoto lens. However, when operating in a studio, a loss of 20% of the wide side of the zoom range could mean placing the camera against the wall to get the blueprint and risk not being able to read the teleprompter due to distance. Consequently, a built-in ratio converter comes to the rescue again. In studio and field lenses, the ratio converter comes into operation automatically when the camera is changed to 4:3.

State-of-the-art studio and field lenses offer digital handling for zoom, focus and iris resulting in faster and more accurate positioning of these important elements. With the recent popularity of computer-controlled robotics, virtual studios and virtual advertising, it is normal to have an RS-232 port on most of these lenses. Data from rotary encoders is available to monitor zoom, focus and iris positions, providing an accurate and continuous feed-back to the computer.

High definition television (HDTV) has already been in the air for many years. However, it was only very recently that some pioneers were brave enough to acquire high-definition equipment. That's changing rapidly and has had a big impact on lenses. Contrary to some rumors, HDTV lenses are not a simple derivative of the NTSC system production line. HDTV lenses are the result of many years of technology development and are vastly different from NTSC lenses. HDTV lenses are designed for higher resolution and much lower chromatic aberration, and mechanical tolerances are kept to an absolute minimum. Because the HDTV system is wider than the NTSC, the resolution of the corners has to be much higher. This is critical when projecting the images onto a large screen. HDTV cameras, and lenses, are a large investment and should be carefully evaluated. Be very strict in your assessment and check each and every one of the available resources.

Unlike NTSC lenses, HDTVs are only available at sophisticated performance levels. Like NTSC broadcast lenses, portable HDTV lenses offer the most advanced digital zoom system, along with all digital advancements. These exceptional products are available as wide-angle zoom lenses with focal lengths from 5mm to 50mm, a standard focal length of 8mm to 120mm and a telephoto lens with a range of 7.8mm to 156mm. HDTV is significantly penetrating the world of feature film and nature documentary, and it is very promising for the future.

Despite being a newcomer to the HDTV market, digital cinema is quickly becoming a reality. For many years, manufacturers of television cameras have been trying to penetrate, without great success, the film industry. The recent introduction of 24P-type HDTV cameras has finally begun to open some eyes. Several films and television specials have been produced in high definition, and tests continue to be carried out almost daily. One of the barriers to the acceptance of this format by the film industry has been the lack of lenses that have the style and quality to which camera operators and producers are accustomed. The recent introduction of lenses to fill these gaps has been met with much acceptance.

The cinema-compatible zoom lenses have the T-Stop scale, are available in wide-angle (5mm-50mm) and with longer zoom ranges (7.8mm-156mm). High-quality lenses, designed from the start to satisfy the most demanding film professional, are now available. These high-quality lenses include cinema-style equipment, visible signals for focus, and a fast T-Stop to compensate for differences in the depth of field of cinema and video. The availability of "cinematic style" lenses opens the door for those producers who see digital cinema as a true alternative to shooting a film.

In short

There are many different lenses available from various manufacturers and all of them serve a specific purpose. Recognizing that it would be great if a lens could be designed to fulfill all the functions everyone wants, that's not the case and never will be. We live in a world controlled by certain physical laws. When selecting a lens for your next camera or project, you should carefully evaluate how the lens will be used and how you want your project to "look." The best camera available can only produce an image from that lens that is recording the scene. If that lens isn't the right one for the application, the end results are sure to let you down. But, with the right combination of camera and lens, that image that you record on the tape will not only be comparable to the view in front of you, but, in some cases, it will exceed what you observed by the viewfinder.