العوامل التي تؤثر في كفاءة غالق الديا فراجم .. كتاب آلة التصوير

Factors affecting the efficiency of the diaphragm shutter

There are several factors that affect the efficiency of the shutter. Its efficiency may be 98% in a group, then it is much less than that and becomes 60% in other circumstances. The following is a summary of these factors:

(a) Estimated exposure time: To clarify this factor, we will assume that the movement of opening the shutter takes 5 milliseconds, and the same time is taken by the movement of closing it, and here we assume the following two shooting cases:

For the first, we estimated an exposure of one second.

In the other, we estimated an exposure of 1/50 of a second.

For the first case, the actual exposure time becomes as follows:

Actual exposure time = shutter speed set in the machine Time taken to open or lock = 1 - 5 / 1000 = 995 / 1000

For the second case, the actual exposure time becomes as follows:

Actual exposure time = 1/50 - 5/1000 = 15/1000 of a second.

... shutter efficiency in the first case = 995 / 1000 : 1 = 99.5%

And the shutter efficiency in the second case = 15 / 1000 : 20 / 1000 = 15 / 20 = 75%
We conclude from the foregoing that the longer the exposure time, the greater the shutter efficiency. The following is an example to indicate the extent of change in the efficiency of an excellent shutter depending on the change in exposure speed:

At one second exposure, the shutter efficiency is 99.5%.
1 / 25. 93%
1 / 50. 65%

And the percentage of shutter efficiency decreases whenever its quality decreases, for example, the shutter efficiency in a box camera decreases and reaches 65% when the exposure speed is only 1/25 of a second, while the efficiency of another shutter in a precision-made camera rises to 93% if the exposure speed is 1/25 of a second too.

(b) The efficiency of the shutter increases as the diameter of the diaphragm aperture decreases: the time it takes to open and close the shutter in front of a narrow aperture decreases due to the decrease in the distance traveled by the shutter blades (Fig. This hole.

(C) The smaller the area of ​​the shutter blades, the greater its efficiency for the aforementioned reason in (B).

Fortunately, most of the types of shutters that are manufactured recently enjoy excellent efficiency even in some types of cheap prices, especially if we compare the current industry with the old types of cameras.