الفرق بين قيمتى المايرد .. كتاب التصوير الملون ، الكاتب عبد الفتاح رياض

The difference between the two Mired Shift values: The optical filters used in color photography change the color temperature of the light rays that reach the color film. In other words, they change the Mired Value.

Assuming that the color temperature of the light rays emitted by the source = Kelvin, then this means that the value of the miled is - = 200. If we put a yellow optical filter in front of the . light source, the color temperature will decrease and become 3200 Kelvin, for example, and thus the value of the meter changes and becomes 312 what is received (refer to Table No. 4 on page 60). Thus, we find that this filter has moved the “value of money” from 200 to 312. The transfer of the value of the Maid was a shift towards an increase, so the value increased as follows:

312 yard - 200 yard = 112 yard. This difference has been called (the difference between the two Mired values). And some other filters (such as blue filters, for example) reduce the difference between the two radius values, so assuming that the color temperature of the radiation emitted by the source = 4000 K (equivalent to 250 radius), then we put a blue filter in front of the radiation source, then its color temperature will increase And become. Kelvin, for example (that is, the equivalent of 200 miles), and then it is possible to calculate the extent of the decrease in (the difference between the two miles’ values) that resulted from putting

Blue filter, in accordance with the following:

20

- = 250 - 200 - 50 what is mentioned.

For the aforementioned reasons, it became obligatory for the difference between the two values ​​of the Mired Shift to be preceded by a positive (+) sign if the shift is towards an increase, or by a negative sign (-) if the shift is towards a decrease.
According to the previous two examples, the difference between the two values ​​of the value must be positive in the first example, i.e. (+112) when a yellow filter is placed, and negative in the second example (-50) when a blue filter is placed.

Thus, we conclude that the yellow filters, although they reduce the color temperature, they always increase the value of the degree (the proportion is inverse). Therefore, the number denoting the difference between the two values ​​of the degree is always preceded by a sign (+) if the filter is yellow.

As for the blue filters, they raise the color temperature, so the difference between the two degrees of color decreases accordingly. Hence, the denoted number must be a negative number preceded by a sign (-) always if the filter is blue. 1

Example 1: Assuming that you use colored film (Kodachrome A.) prepared for imaging in the rays of a light source whose color temperature is = 3400 Kelvin, but by measuring the color temperature of the rays of the light source that you had at that time, you found it = 3180 Kelvin, which calls for choosing a light filter Suitable, so what filter do you choose (among the Kodak Wratten filters that came in Table 5 on page 64).

the answer :

3400 K = ... what is received

3180 Kelvin - what is mentioned

...

It requires searching for a filter that conveys the value of the Maird from:

294 - 314 = - 20 miles

Refer to the Kodak Wratten Light Filters table

Balancing filter We find that the closest filter capable of transmitting the value of the meter by (-- (20) is the 2 Watten blue filter.