Darkness: A Dedicated Cinema's Best Friend!
You have probably heard us recommend the advantages of calibrating audio visual components to ISF (Imaging Science Foundation) standards. Michael Levy is an audio video consultant on Long Island, New York USA and has had a wealth of experience as a trained ISF technician – he really knows his stuff.
The following brief article looks at his real-life movie-going experiences as a young person; explains just how a Director influences what you see from a technical viewpoint and how variations in light affect the end result. There is also a link at the end to an article that discusses the advantages of ISF calibration, something every serious home cinema enthusiast should have performed.
As a child, Sundays were frequently spent at the local Movie Cinema. It truly was a paradise for me. How little I knew back then that I was watching a medium at the height of its glory. The screen was huge and often opened into panoramic width. There were dimly lit stars on the ceiling, feigning a midnight sky as I watched the stars on the screen. Everything was dark maroon. The seats and the walls were velvet. The only lights during movies were dimly lit guides to your seat on the floor. My first memories of it were from when I was very young. I was small enough to sink into the plush seat and in love with movies enough to be lost in the new world on the screen projected through the darkness. Yes, darkness, an important point. For maximum enjoyment of the movie experience, you must allow yourself to temporarily forget your surroundings. In darkness, you can transcend the space between you and the screen and go into its world.
I remember the premiere of “Cleopatra,” starring Elizabeth Taylor and Richard Burton. It was an event, and it all began when the lights went off. The screen was huge and curved, almost wrapping itself around me. I was transported into a majestic ancient world. There were ocean battles and ancient armies and Rome in all its splendour. The theatre had done its job, for it had temporarily ceased to exist in my mind.
If you want to see film in its best environment, there are only a few state of the art movie theatres still in operation. The only one near me closed a few years ago. I now need to go to the Ziegfeld Theater in Manhattan, an hour and a half away, if I want to see a 70mm movie as it was meant to be seen. It is worth the trip. The depth of colour and detail are unparalleled. To me, this is the reference.
The Director’s Objective
Directors design their films to be viewed in state of the art cinemas. When filming a movie, the director has brightness and colour values he or she wants on the screen, based on the end result being viewed in darkness. If you change either the environment or the medium reference values, you chance changing the very meaning of a scene. Changing the reference colour temperature, or the reference white level, or most importantly the reference black level, changes the effect of the scene. How bright or dim an image is defines how it feels to the audience. Misty or dimly lit scenes like the scenes inside the caves in “Star Trek: Insurrection” or its highly contrasted outdoor scenes impart a feeling that is lost if the dynamics of the lighting of the scene are changed. Even a small amount of light in the room or on the screen will mute the perceived dynamics. In order to achieve the director’s desired effect, the home viewing system and environment must have light levels that come as close as possible to the reference movie theatre.
The Effect of Black Levels
The movie theatre is a controlled environment based on a black background and very specific lighting values. There is a maximum light level (10-foot lamberts reflected from the screen on a pure white frame) and a reference colour temperature. All of the colour values are based on these. What about the reference black level? There is none. You just want to get as close to absolute black as possible. Film black level is excellent, but it is not the absolute black that can be had on a CRT-based system. A CRT-based system can achieve black levels that make images pop out in a way film cannot, but if film is the reference, and directors work with it in mind, then the system should at least be able to achieve film-level black.
Film is a “pass-through” medium, meaning that light is filtered through it. Some light passes through even the darkest black on film. The mechanics of a light filtering system make achieving what we would perceive as absolute black impractical. Film is also an analog medium, meaning that it can show all values of colour and gray from the projector’s darkest black to its maximum output.
Video Vs Film
Video systems differ in many ways from film. While film shines light through an image on a sheet of celluloid, video systems chop up the picture into little pieces, then put them back together to create an image. The most basic element of a video image is the pixel. It shows us a light value at a particular point on the screen at a particular time. The number of pixels used dictates the detail level, and the light they put out, dictates how well the video system can achieve the reference light values. The values of gray displayed are discrete, but if there are enough levels of gray, we don’t notice them; if there are enough pixels, these should be too small too be seen at the normal viewing distance and meld in our eyes into a contiguous image.
Rather than our eyes, I should really say our minds, for it is how our minds use our eyes to see that is the entire basis of the magnificent deception that is the cinematic experience. We watch an image on the screen that has a maximum light output that is not even as bright as a well-lit room at night, and we can deceive ourselves into thinking we are looking at ancient Rome in a brightly lit outdoor scene. What is it that allows this deception? In order for us to see in the vastly different lighting that is indoors or at night as compared to outdoors on a bright day, our eyes and minds compress the lighting dynamics. Our irises open and close to accommodate the available light, and our minds process differences in light level logarithmically. This means, as an image gets brighter, our eyes become less sensitive to light variations. The effect is that it is the relative light level that we see, not the absolute light level. Therefore, if our eyes settle into the darkness of the movie theatre, a mere 10-foot lamberts of light can look like an outdoor scene that originally measured over 1,000. If a little light is allowed to corrupt the black level, our eyes readjust and the lighting dynamics break down.
Television lighting dynamics are made for a dimly lit room. The reference peak white for a television is 30-foot lamberts. It is designed for the viewing dynamics to stay approximately correct in normal night time lighting. We do not view TV the same way we view movies. Our attention is not always on the TV, so it is acceptable and expected for the rest of the room to be lit.
I am, though, perplexed by the new plasma screens offered by one manufacturer. Phillips has added back lighting to their flat panel TVs. The back lighting matches the colour and dynamics of the image on the screen. This defies everything I know as a professional video calibrator about how the eye perceives an image. The back light will destroy the perceived image dynamics, and making it the same colour as the image on the screen will mute the colour dynamics. When the light in a room is of a particular colour, our eyes adjust instantly so that we can better perceive colour variations. If our eyes see light that is the same colour as the colours used in the image on the screen, they will adjust to see those colours less and all other colours more. A good example is lighting in the home. The incandescent lights in most homes have a colour temperature of about 3000K. That means that their light is quite yellow, but we don’t notice as our eyes quickly adjust.
Understanding how our eyes and minds perceive light is basic to our understanding of what parameters to look for when choosing a projector for a home cinema. Projectors are usually marketed to us like light bulbs: the brighter the better. The home cinema’s reference lighting parameters tell us something else. To achieve those standards, we must select a projector with light output that matches the size and reflectivity of the screen we will use. Too much brightness (from the screen) will ruin the image dynamics, because it will destroy the perceived level of black. You cannot solve this problem by simply turning down the contrast (white level) on the projector, because that will not alter the black level. The reference black level of a projector is determined by its maximum light output and contrast ratio. This is why many of the better home cinema projectors now sport irises to adjust the light output from the bulb.
Without question, the most important colour in a home cinema is black. The effect of a director’s carefully designed scene can be destroyed if the black level is wrong. One of the best tips (if not the single best) I can offer the home cinema enthusiast is to keep those lights off when watching a film.