طرق إعداد ( المعاصرة ) في آلات التصوير .. كتاب آلة التصوير

Methods of preparation (contemporary) in cameras:

It used to be the practice in the past that the photographer himself perform the process of contemporaneity, by opening the shutter at the T or B sign, then igniting the flash light powder, then closing the shutter after the flash and the end of the exposure, then the mechanical and electromagnetic means that are prepared in the camera during its manufacture were introduced.

The method of setting the press between the shutter and the lamp is considered an extensive study in itself and requires previous mechanical and electrical knowledge, so we pass it here quickly and briefly to the extent that we need in practical application in photography only, and for this reason we suffice here with an enumeration. A brief summary of contemporary methods in the shutter of the camera.

1- Electromagnetic Synchronisation

As soon as the electric current drawn from the battery reaches the lamp, the developments that lead to the ignition begin, and as we know it takes a time for the flash to reach the peak, ranging from 15-30 milliseconds, depending on the type of lamp, which is enough time for the shutter to reach its maximum amplitude while the light energy reaches its peak also .

We see in (Fig. 205) the method by which the shutter is prepared to open in an electromagnetic way, whereby the electric current passes in a coil around a piece of iron that is immersed in the passage of current around it, so a small iron lever is pulled towards it and this latter presses on the arm of the shutter during the movement of attraction, so it opens it, and he watches The shape also contains a container nail to determine the necessary distance between the magnet and the lever.

Whereas it takes more time for the magnet to attract the lever than the time required for opening the shutter, so the time required for these two operations is calculated together so that the flashing light reaches the top contemporaneously with the moment the shutter opening reaches its maximum width as well.

2- Mechanical Synchronisation:

The mechanical press method performs two functions: the first is to press a button to deliver the electric current to the lamp, and the second is to press the shutter trigger after an appropriate time so that the maximum aperture is pressed to the top of the flash. (Fig. 207 and 206) illustrates the mechanical way in which the press is carried out. If the black lever shown on the left side of Figure 207 rises, the zipper will go down (Fig. 207), and in this movement the electric current circuit is connected as shown in (Fig. 207) and then it runs The zipper is in its descent to press the lower pin, and the shutter opens.

The relationship between contemporary and (delay):

We have already talked about what is meant by the expression (delay), and we understood that it is the time that passes from the moment the shutter trigger is pressed until the flash of light reaches its peak. The “delay” may be very short, i.e. about 5 ms, or it may be relatively long, i.e. about 40 ms, for example.

Undoubtedly, there is a close connection between the timer and the “delay,” as the setting of the timer in the shutter must be appropriate for the delay. If the shutter takes 30 milliseconds to reach its maximum width, then this time must be sufficient for the flash to reach to the top too.

As desired, the markets come with different types of flashing light lamps, so the delay time also differs in them, so the camera factories used to prepare the shutter to work in a way that suits all. Flashlight lamps are in circulation, whether they have a short delay or a long “delay”. Therefore, most modern cameras are equipped with signs indicating the type of press for which the shutter is prepared, i.e. are they fast presses suitable for flash light sources with a short delay such as 6 milliseconds, or Slow refresh is suitable for sources with a long delay, such as 40 milliseconds, for example.

For this reason, we find signs on the camera that determine the type of contemporary suitable for the flash light source. The X mark indicates the appropriate rate for short delay sources, and indicates that the flash does not occur until the shutter has reached its maximum width. Whereas, the .M sign indicates the appropriate contemporaneity for sources with a relatively long delay (this letter stands for Medium).

It remains for us to know what lamps are suitable for contemporary X. Synchronisation, and those that are suitable for contemporary M. (i.e. Medium Fast Synchronisation). Contemporary type suitable for the lamp used, and it is not difficult to know that by reading the brochures of the flash light lamp and its properties.