Autofocus tracking

Autofocus tracking, tracking it in English autofocus, autofocus and provides a predictiveautofocus. The action of this type of focus in the model Canon EOS-1D Mark IV is a verycomplicated description can be postudiować in this document called the White Paper,of course, English. In our FOTOPORADNIKU let us quote a simplified description of how such a system. That track is a continuous course focusing on a moving object, which is approaching ormoving away from the lens. The points can describe it anyway.

- Camera control program forograficznym "fishes out from the frame a distinctive objectwhich" nacelowaliśmy "our camera. Let this object changes the distance from the camera, which is approaching or moving away from us.
- The program sets the lens so that the image of the object was sharp. This takes about 1 / 100 sec lens settings are stored.
- After a short time as possible (say, 0.05 s) the program re-focusing. The new settingsare stored lens too. The program compares both the lens settings and their values ​​are determined direction of movement of the object and its speed to the camera.
- Press the shutter button to take a picture. The program knows the time of pressing theshutter button until it opened and already knowing the speed and direction of thephotographed object, the program sets the lens so that the image of the object when theshutter speed was sharp.

Multi-point AF

Image produced by the lens is projected, through the arrangement of mirrors, an additional sensor (or several dies) dedicated to focusing. On this matrix are separate areas are arranged so as to cover the entire frame "seen" to postpone the lens.Depending on the sophistication of a digital camera model, these areas can be from several to several dozen. Canon EOS-1D Mark IV is the 45 Each of these areas, popularly known as the point, though this is an area of ​​specific dimensions, serves to focus on him for a portion of the projected image.Focusing is based on such a draw position of the moving lens in the lens to get the greatest contrast. In contrast, a simple apparatus is selected relative vertical edges visible in the frame. Hence, known fault CDs that can not set the focus to the boat on the water, where lines of different areas of the frame are horizontal contrast. In the case of the EOS-1D Mark IV, but many other SLR cameras and the contrast is determined by the vertical and horizontal lines. Called a "cross" area. Of the 45 areas the designation field 39 is a cross areas. Focus is on
capturing an image incident on a point (area) measurementsetting the contrast for the image, which is part of the whole frame projected on the main matrixadjustment of moving lens elementsdetermine whether the contrast has improved or deterioratedwhere the contrast has improved, rules, setting the lens is repeated in the same directionif the contrast worsened, adjust the lens is "the opposite" direction.this method, step by step, we select the greatest contrast, namely setting the lens gives the best focus for the objects seen in the measuring area.Such wyzaczenie focus requires intensive computation and high-speed transfers of lenses in the lens. Calculation of designating a separate processor performs the focus, in case of the EOS-1D Mark IV is 40 MHz, 32-bit RISC on the structure. These calculations are spomagane by the main camera processor - 40 MHz, 32-bit RISC too.