Perhaps the main victims of the migration to HD are the art directors. For good or for Badly, the new cameras have contributed dramatically to complicate their lives, because as we say when we are in trust, they don't forgive a single one. A set for HD production must be perfect in all its details, point. It is another of the prices that we must pay for the high definition.
But leaving aside the aesthetic aspects of the HD production, another guild suffers the consequences of work with better quality images: that of the cameramen. Many of them have found that it is more difficult to maintain the focus with an HD camera, especially when there is not much light. After several decades of reneging on the old school, many photographers have been learning to consider assisted focus systems as a blessing to which only those who work have access with the most economical cameras.
And what can those who only have in their lens of several thousand dollars a focus ring without servo mechanisms of any species? The task of focusing in HD when wearing lenses Serious is complicated because, in many cases, the signal what the camera operator sees is not a real HD signal. Some ENG/EFP cameras have come to make concessions so atrocious how to use tiny color LCD screens as camera viewfinders. This explains the fashion of HD screens mounted precariously on cameras of all kinds: the truth is that the size of a conventional viewfinder does not allow ensure an accurate focus.
Consider, in addition, that many cameras destined for the world of the television have been incorporating optical adjustments that eventually allow to drastically reduce the depth field. Directors and filmmakers are increasingly committed to compose 16:9 frames with angles that allow you to make games of depth and focus changes that can become a nightmare the slight touch of a focus ring, which in the SD world meant being prepared for a quick adjustment, it can irretrievably damage a plane or, even worse, generate an image with soft focus capable of becoming a nightmare for post-production people.
Thanks to the little ones
The industry has generated solutions for this situation that, mostly, they come from the camcorder market of professional type, who usually make compromises between the total automation of home cameras and control absolute of the cameras of the broadcast world. In this Regardless, it is worth taking a quick look at the solutions of assisted focus of some low-cost camcorders .
For example, Sony's famous Z1 finally managed to put it to use. smart to the infamous zoom concept digital that afflicts most camcorders Domestic. The ability to enlarge the image is applied to expand the middle part of the box and match it, pixel per pixel, with the physical resolution of the outer display of the camera, which becomes an invaluable aid to achieve precise focus in difficult conditions. This idea brilliant for its simplicity has found a space in camcorders high-end as elegant as thomson's Infinity, which from its first version has a button to do exactly what same.
Some high-end camcorders , from Canon and Panasonic, offer the possibility to choose various modes of operation for your light-based autofocus systems Infrared. This development comes directly from the world of SLR photography cameras, which for a long time offer different programs for focus assistance, and that have recently begun to appear in lenses for ENG applications from all manufacturers, which although they do not have the talent needed to stay in focus, yes can set a starting point with a good level of reliability.
This ability to manage servomechanisms of the cameras to set default positions, gives foot to one of the most frequent characteristics in camcorders professionals: the possibility of setting ceilings or key positions and make automated movements between such points. This functionality has also begun to appear in the high-end lenses, with the advantages brought by high-precision servo mechanisms.
Sony's EX1 is another source of inspiration. The ring of Focus of your lens allows you to use an assisted focus system when it is pushed forward, and when it is carried backwards it is pushed forward actuates a clutch that allows the operator to push physically the jagged rings that move the elements of the lens. Sounds like an almost perfect solution: shift from focus fully mechanical to totally lazy focus with a slight finger pressure. But, unfortunately, the servos of the Fixed lens of the EX1 only go as far as its price Allows. And some mechanical peculiarities of zoom lenses Serious make this system not so easy to deploy to products intended for applications ENG/EFP. However, that the idea appears in that market, is only a matter of time.
To top off this issue, in many domestic camcorders of recent model, of those that sometimes have interfaces of user only suitable for children under 14 years, have appeared zone-assisted focus systems, in which the user defines a window that is supposed to contain the part of the image that it must be kept in focus. Apparently, this system uses the contrast values of the generated signal to keep in focus the demarcated area in the viewfinder, which is actually the result intelligent. And in the most sophisticated lenses on the market is a very similar system is beginning to appear.
Lenses with windows
A good example is the latest models of the Canon series Digisuper, which include an automatic focus system that allows the camera operator to set a window that delimit the area where you want to get the most accurate focus. The electronics of the lens generate the frame of the chosen area and the makes it appear in the camera's viewfinder. All options The AF system of Digisuper lenses are operated from the lens It includes a very simple interface based on a small joystick and some buttons that are activated from the remote focus.
The AF system of Digisuper lenses offers two modes of operation: first, a part-time one in which the autofocus operates as long as the operator holds down a button. Second a full-time one that keeps the focus constantly on the objects that are inside the selected window such as a race car that comes towards the camera and that the cameraman continues with a panning rather fast. This seems too good to be true, but it works surprisingly well.
The obvious question is how an autofocus system is achieved. really functional in large focal length lenses, some of them they specially designed for sports productions. Is evident that the Digisuper 100AF cannot use a system infrared to estimate distances, for example. The answer no it's simple. The name Canon gave to the measurement system is intimidating: Through-the-Lens Secondary Image Registration Phase Detection, or TTL-CT-SIR. What in Castilian could be called something like Detection of the phase of convergence of the image through the lens. And explained in the simplest possible way, means that Canon has managed to generate useful information about acuity of the image before it reaches the focal plane.
And how is this magic achieved? Essentially, the lens includes a pair of CMOS sensors and a secondary lens system that allow to estimate very accurately the quality of the image that it is delivered to the back of the lens. The measurement of zones in particular it is achieved simply by means of an analysis in real-time difference between the image recorded in the same area of the two sensors. For practical purposes, what it happens is that the difference in the image captured by two video cameras that are included inside the lens, and this information is used to control the servos of the lens and keep the focus on the selected window.
Now, this autofocus system is not a novelty for users of Canon camera lenses. Many EOS lens users enjoy its benefits, although most of them do not have in their lenses the kind of servomechanisms that allow you to make the complete route of a zoom 100X in half a second. And this is another proof that the Innovation that moves our industry continues to come from the consumer equipment.
This system of focus measurement by comparison is being becoming an industry trend. Fujinon presented at NAB 2008 a similar system in its DigiPower lenses, which despite some implementation differences, it operates on a basis on the same principles. Unfortunately for the immense base of users of handheld HD cameras, this type of solutions for assisted focus is still a long way off, as accommodate the hardware needed for optical focus measurement in the chassis of a lens for ENG applications is going to be a complicated task. But it's only a matter of time.
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