How to calculate and modify the exposure time in the color correction process?

To calculate and modify the exposure time according to the sample, we must first know that the three factors that cause the exposure time to change in the color calibration process (ie, the density of the color correction filter, the number of sheets, and the sample density, etc.) are at the exposure time. Change the value and then calculate the new exposure time based on these values.

(1) Influence of filter density variation on exposure time In general, the effects of magenta and cyan filters on the exposure amount are basically the same. When each density is increased or decreased by 10, the exposure time also needs to be increased or decreased by 10%. The yellow filter has less influence on the exposure, and the exposure time differs by only 10% when there is a difference of 40 densities. Calculate the following two tables for reference when calculating the exposure time. Effects of Magenta and Cyan Filter Density Changes on Exposure Time

(2) The effect of changing the number of filter sheets on the exposure time Generally, the transmittance at the new color filter is good, and each filter differs by 10% of exposure. If the color filter is worn out and the surface is rubbed, the light transmittance will decrease, and each filter will have a difference of 15% or more in exposure time. Effect of Change in Number of Color Filters on Exposure Time

(3) Influence of sample size on the exposure time The exposure time is too much or too short, according to the amount of excess or deficiency (percentage) calculated according to the data in the table to modify the exposure time. Sample exposure density (dark and light) changes to the exposure time. Two examples are given below to illustrate the calculation method for modifying the sample exposure.

Example 1: The original sample filter combination is 604000.

Exposure time: 10 seconds

Number of filters: 2

After the sample is judged by the sample bias magenta, it is estimated to increase the density of 20 magenta filters. The sample density is low, it is estimated to increase the exposure by 10%.

Therefore, the modified filter combination is 606000

Check the table, increase the density of 20 magenta should be × 1.2

The number of filter sheets has not changed

Check the table, the density is too small 10% should be × 1.1

Therefore, the change exposure time is: 10 (seconds) × 1.2 × 1.1 = 13.2 (seconds)

Example 2: The original sample filter combination is 403000

Exposure time: 15 seconds

Number of filters: 2

After the sample was judged: the color yellowish 30 density, partial green 15 density, the sample lighter than 20%.

Therefore, the modified combination of color filters is: 403000+300015703015-151515551500

The revised changes are:

Yellow filter increases 15 density × 1.05

Magenta filters reduce 15 densities by 0.85

Color filter increases two x 1.2

The modification of the exposure time should be:

15 (seconds) x 1.05 x 0.85 x 1.2 = 16 (seconds)

Reproduced from: Dot sight