JPS6046693B2 - Color printer - How to change the correction level - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the automatic exposure control method of a color printer, and when making a color print from a color negative.
This invention relates to a method in which the correction level of a color printer can be freely changed by comparing and calculating the exposure amounts of three colors and changing the constant exposure amount.

First, in order to facilitate understanding of the present invention, a method for obtaining a positive image on color photographic paper from a color negative image using an automatic exposure control color printer currently in practical use will be explained.

When printing from a color negative onto color photographic paper, the exposure amount Hi for each color on the color photographic paper is expressed by the following equation (1).

1:B. ．． G. ．． Rt: Exposure time It: Illuminance on the photosensitive surface of the photographic light-sensitive material By controlling the exposure amount of each color to be constant, the function of the printer's exposure time based on Evans' printing theory can be expressed as F. Then, this is the following equation (2
).

Taking the logarithm of equation (2), where T: Average transmittance of color negative 10: Illuminance of incident light to color negative K: - Constant based on the combination of a certain printer and a certain color photographic paper D: Average transmission of a color negative Density These Evans theories are employed in most current color printers and form the basis of the color printer that is the object of the present invention.

Automatic exposure system of conventionally known color printers. As a control method, the illuminance on the photosensitive surface of the photographic light-sensitive material that has passed through the color negative is photoelectrically converted, and at the same time as exposure begins, a photocurrent proportional to the illuminance is charged to a capacitor, reaching a reference voltage corresponding to a constant amount of exposure. Constant exposure control that ends the exposure when A system is known, and FIG. 1 shows its basic circuit.

In Figure 1, the output voltage of operational amplifier 0P1 is VOPl
This is expressed by equation (4). In the figure, P
T is a photodetector, C is a capacitor, S is a relay contact, -
h is a photocurrent (Ip>0), and VC2 is a reference voltage corresponding to a constant exposure amount. The above circuit consists of a photocurrent integration circuit using an operational amplifier W) P1 and a reference voltage V using an operational amplifier 0P2.
It is composed of a comparison circuit with C2, and the output voltage (■0P1) of equation (4) and the reference voltage V.

2 are compared by the operational amplifier 0P2, and ■0P1=V
Exposure ends when C2 is reached.

That is, when the equation (5) is transformed, the equation (1) and the equation (5) correspond to each other, and the equation (2) and the equation (6) correspond to each other.

Now, it is practically difficult to faithfully reproduce Evans' printing theory using an automatic exposure control method using equation (5), and in actual color printers using an automatic exposure control method, (3)
The formula is as shown in Figure 2 for standard color negative (DNllO
Each automatic exposure controller has its own correction coefficient C, and depending on the type of automatic exposure controller, Points (1) to (1) that deviate from the ideal or theoretical state
Color negatives affected by 5) will result in inappropriate print finishes.

Therefore, it is an object of the present invention to obtain an appropriate print finish by changing the correction coefficient or correction level. The color balance in color negatives, or the ratio of integrated transmittance of blue, green, and red, is affected by the following main factors.

(1) Shooting with a light source that deviates from the specified color temperature.

(2) Improper or too long storage of color negatives.
(3) Variations due to color negative manufacturing rods and processing changes.

(4) Over or under exposure of color negatives.

(5) Color subdivision area. When a printer (C, = 1) that faithfully follows Evans's printing theory, that is, the integral neutral method, has exposure conditions set so that it will produce a reasonably good color print when printing with a standard color negative, ) When printing negatives affected by factors (1) to (4) above,
This will produce a high print finish that meets your expectations, but if you print a negative affected by factor (5), it will exhibit an inappropriate color balance, so setting the correction coefficient to C or 1 will produce an optimal print. What I can confirm is that
This is common knowledge in the industry.

However, as mentioned above, each actual automatic exposure machine has a unique value of C, and generally this C is determined by the factor (
4) can be changed to adjust print density and color balance, but in this case B. ．． G.
R#. Since the value C,=1 is not taken, even if factor (4) is satisfied, optimal correction cannot be given to all factors (1) to (4).

Therefore, the objects of the present invention are (1) and (1) listed above.
It is an object of the present invention to provide a color printer correction level changing method that can obtain color prints that are satisfactory also from the factors 2), (3), and (5).

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In a color printer that uses an automatic exposure control system that follows the average transmission density of each primary color in a color negative film to be printed, which has a control circuit as shown in FIG. 1, an appropriate color print can be obtained from a standard color negative, and When the exposure conditions are set so that the color exposure times t are equal, when printing with a color printer that prints an actual color negative influenced by the factors (1) to (5) listed above, each primary color The exposure time is different from the exposure time of the standard color image, causing a difference in the slope ^·h of equation (5). As described later, the present invention utilizes the difference in the slope of each primary color from this standard slope, and sets the first standard exposure amount during the transition until reaching the second standard exposure amount corresponding to the constant exposure amount. The gradient difference detected and stored at this first reference exposure amount is used to change the second reference exposure amount, thereby changing the coefficient C. Figure 3 shows
This is a graph of the exposure setting equation (5) in which the exposure time of each color is adjusted equally so that the standard color negative print becomes gray or a hue close to gray, and the exposure time is TN.

Figure 4 shows the deviation of the exposure time of a color negative taken with a fluorescent lamp that falls under factor (1) from the exposure time of a standard color negative under this exposure setting.
, t7 are respectively B. ．． R,. It is assumed that the exposure time is G and that the print at this time has a yellow-green finish.

FIG. 5 shows the variation of the exposure time of a color negative photographed with the same exposure setting of a red subject that falls under factor (5), and TlO, tl3, and tl5 are B. ．．
G. ．． It is assumed that the exposure time is R (TlO and tl3 may be reversed) and that the print at this time is finished in a complementary color of red, that is, cyan. A method of changing the correction level of a color printer according to the present invention when printing a color negative will be described below. Although the correction level of the automatic exposure controller assumed as above is C<1, it is not a very low value.

(See Figures 6 and 7) At this time, the value of Ci is C. Set it to 6.

Also, for simplification, when i in equation (7) is set to B=G=R and equation (7) is assumed to be a common 10gF'=K+COD-(8), exposure times T4, t5, t7, tlO, tl
3, tl5 is located somewhere on the line of equation (8). FIG. 6 shows T4, t5, t7 shown in FIG.
FIG. 7 is a diagram illustrating a state in which TlO, tl3, and tl5 shown in FIG. 5 are located on equation (8).

Therefore, in order to bring CO (ku1), which is unique to this automatic exposure machine, closer to 1, as shown in Fig. 6, and its C. In order to make the value smaller, equation (8) can be moved in the direction of the arrow as shown in FIG. That is, in carrying out the present invention, C
If it is necessary to bring O=1 closer to 1, shorten the first exposure time, make the second and third exposure times longer, and set T4, t5, and t7 as indicated by the arrows as shown in Figure 6. Just move in the direction.

Also, with some automatic exposure machines, the purpose of changing the correction level can be achieved by changing only the shortest exposure time.
This degree of correction may be changed appropriately. In this way C. =
By bringing the value close to 1, for example, a color negative print photographed under a fluorescent light can be printed with an appropriate finish. In addition, it is possible to create an optimal print finish by changing the correction level even from color negatives affected by the above factors (1) to (4). Furthermore, when printing a color negative photographed with a red subject such as the one described above using such an automatic exposure machine, in order to ensure that the print has an appropriate print finish, set the correction level to C.

In this case, it should be smaller than , as shown in Figure 7. , Tl3, and Tl5 in the direction of the arrow, a proper print can be obtained. In other words, if the shortest exposure time is made longer and the second and third exposure times are made shorter, the correction level becomes C. It is possible to create a desirable and appropriate print finish from a color negative affected by the above factor (5). Further, the degree of correction may be changed as appropriate from the above. Next, a specific method of calculating the value at which the second reference exposure amount should be changed when carrying out the correction level changing method according to the present invention will be explained using FIGS. 3, 4, and 5.

That is, according to the present invention, the second reference voltage (2) corresponds to a constant exposure amount in the relationship of equation (5) above.

2, in order to determine whether the exposure time of the color negative deviates from the exposure time of the standard color negative, the first reference voltage VOl is determined, and it is determined whether the exposure amount of the three colors increases with the start of exposure. This is the first reference voltage V.

The exposure amount of each color is memorized at the instant when the exposure amount reaches l. That is, in FIGS. 3 to 5, the exposure amount is stored as follows. FIG. 3: At exposure time t1, B. ．． G. ．． R and ■.

Remember 1. Figure 4: At exposure time, B:■1
, R: VO3, G: C4.

Figure 5: At exposure time t, B: ■1, G: ■.

5, R: ■Memorize 06.

According to the present invention, from the first reference exposure amount VOl to the above-mentioned stored exposure amount (■) for each primary color. , VO4, ■. 5, the value obtained by subtracting V06, or the above-mentioned memorized exposure amount for each primary color. The constant exposure amount is changed by adding or subtracting the value obtained by subtracting the average value of , or the value obtained by multiplying these values by an appropriate multiplier (α) from the second standard exposure amount of each primary color, but these In figures 4 and 5 it is indicated by ΔV.

That is, ΔVl, ΔV2, and Δ■3 in FIG. 4 are given as follows.

Alternatively, ΔV4, ΔV5, and ΔV6 in FIG. 5 are given as follows.

Alternatively, in the above formula, α1 to α8 are each 1 or a multiplier appropriately determined based on empirical rules.

ΔV1 is the first reference voltage VCl and the exposure amount ■ of the second and third exposure times. 3. ■The difference between the average values of 04 multiplied by α1, or ■C1 and the 1st, 2nd, and 3rd exposures■
The difference in the average value of Cl9VC39■d is multiplied by α2, and as shown in FIG. 4, the second reference voltage ■.

2 by ΔV1, the exposure time is shifted from T4 to T3, and the shortest exposure time is made shorter.

ΔV2 is the first reference voltage VCl and the exposure amount ■ of the second exposure time.

3 is multiplied by α3, and as shown in Figure 4, ΔV2 is added to ■4 and the exposure time is shifted to T6.
The second exposure time is made longer.

ΔV3 is the difference between the first reference voltage ■1 and the exposure amount VO4 of the third exposure time multiplied by α4, and as shown in FIG. 4, ΔV3 is added to ■4 and the exposure time T7→ ! , and the third exposure time T7 is made longer.

ΔV4, ΔV5, Δ■6 are calculated in the same way as Δ■1, Δ■2, Δ■3, and in Fig. 5, ■2+ΔV4, VO2
-ΔV5, VC2-Δ■6, the constant exposure amount is changed, and the exposure time Tl.

, tl3, tl5 are TlO−+Tll, Tl3, respectively.
- Tl2, Tl5-Tl4. Also the third
As shown in the figure, in the case of standard color negative, constant exposure amount VC2
remains unchanged. In short, the method of the present invention is based on formula (9) ~
A second reference voltage corresponding to a constant exposure amount is determined using values such as equations (15) and (16) to (22). is varied, and formulas (9) to (15) are calculated according to the factors of the color negative film.
The present invention provides a color printer correction level changing method in which the print finish is made appropriate by manually switching between the equation and equations (16) to (22).

In carrying out the method of the present invention, the above ΔV1 to ΔV
An implementation circuit that operates to add or subtract a value such as 6 from a constant exposure amount may be incorporated into a color printer, but FIG. 8, which shows an example of an implementation circuit related to FIG. 4, will be explained in detail below. .

In Fig. 8, the blue, green, and red lights transmitted through the color negative are converted into photocurrents by photodetectors 1, 2, and 3, respectively, and at the same time as exposure begins, contacts 4, 5, and 6 are opened and integrated into an integrating capacitor. 7, 8, and 9 are charged with photocurrent of each primary color,
The outputs of the operational amplifiers 10, 11, and 12 are respectively BlG. ．． Draw a straight line R. Resistance 13, 14, 1
5 each? Ω, resistor 17 to 1KΩ, and resistor 16
, 18 are made equal, the output of the operational amplifier 19 is as follows.

Further, if the resistors 20 and 22 are equal and the resistors 21 and 23 are equal, the output of the operational amplifier 24 is (first reference voltage V.

l-output of the operational amplifier 10). Similarly, resistance 25,
27 and resistors 26 and 28, the output of the operational amplifier 29 is . ．． One... ．． ,,,
．． ．． ．． 、． ---. ．． ．． −, with resistance 30,3
2 are equal and the resistors 31 and 33 are equal, the output of the operational amplifier 34 is as follows.

A combination of capacitor 39 and operational amplifier 40, a combination of capacitor 41 and operational amplifier 42, a combination of capacitor 43 and operational amplifier 44, a combination of capacitor 45 and operational amplifier 46, and contact 3 of relay 79.
5, 36, 37, and 38 constitute a memory circuit.

Any one of the outputs of the operational amplifiers 10, 11, and 12 is the first reference voltage ■. 1, when the relay 79 is activated, the contacts 35, 36, 37, and 38 are opened, and at the instant of exposure time T2 in FIG. operational amplifiers 40, 42, 44,
46.

The output equations (27), (29), and (30) of the operational amplifier 40 are each expressed as (12)
, (15), and (14).

It is assumed that the relays 80, 81, and 82 are related to blue, green, and red, respectively, and when any one of the outputs of the operational amplifiers 10, 11, and 12 reaches the first reference voltage ■1, If only the relays of that color are activated, only the blue relay 80 will be activated and the relays 80 and 81 will be activated with respect to FIG.
, 82, the contact 53 is closed.

From the above, the resistances 47, 48, 49, 50, 51,
52, 56, 57, 58, 60, 61, 62, 64, 6
5 and 66 are all equal, the outputs of the operational amplifiers 59, 63, and 67 corresponding to blue, green, and red, respectively, are as follows.
After the exposure time shown in FIG. 4, the following happens.

Comparators 85, 86, and 87 corresponding to blue, green, and red are as follows:
Comparing the output of the operational amplifier 10 and equation (31), the output of the operational amplifier 11 and equation (32), and the output of the operational amplifier 12 and equation (33), respectively, the following equations are obtained: (32),
When the equation (33) is reached, comparators 85, 86, and 87 generate blue, green, and red exposure end signals.

The comparators 68, 69, and 70 compare the outputs of the operational amplifiers 10, 11, and 12, respectively, with the first reference voltage (1), and determine that they are the first reference voltage (2).

When reaching one, the outputs of comparators 68, 69, and 70 go from the binary value "0" to "1" and are applied to the input of OR gate 71.

When even one input of the OR gate 71 becomes ゛゜1゛, the output of the OR gate 71 becomes ゛゜1゛, and the output is supplied to the set input of the flip-flop 75 which is in the reset state, and the flip-flop 75 is set. state, and the relay 79 is activated. flip flop 76,7
When 7 and 78 are in the reset state, NAND gate 8
The output of 3 is "0", the relay 84 is not activated, and the contacts 72, 73, 74 of the relay 84 are closed, and the output of the comparator 68 corresponding to blue becomes "1" first, so it is a flip. - Among the flops 76, 77, and 78, the flop 76 is set first, the relay 80 is activated, and its contact 53 is closed.

When the flip-flop 76 becomes set, the output of the NAND gate 83 becomes ゛1゛, and the relay 8
4 is activated and its contacts 72, 73, 74 are opened, so the flip-flops 77, 78 cannot be set, so the relays 81, 82 are not activated and their contacts 54, 55 are open. It remains as it is. In addition, flip
The flops 75, 76, 77, and 78 are supplied with a reset input after exposure and return to the reset state.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a constant exposure control circuit, Figure 2 is a circuit diagram of a constant exposure control circuit.
The graph of gF, = K, +C, Di, Figure 3, is
Figure 4 is a graph of the transient phenomenon of equation (5) when shooting with a standard color negative, and Figure 4 is a graph of the transient phenomenon of equation (5) when shooting with a color negative using a fluorescent lamp. , a graph showing the transient phenomenon of equation (5) when photographing a red subject with a color negative; Fig. 6 is a diagram showing the positions of ζ, T5, tN, and t7 on equation (8); Fig. 7 The figure shows TiO,tl
3. Diagram showing the position of tN, tl5 on equation (8), No. 8
The figure is a circuit diagram showing an example of the implementation circuit related to FIG. 4.

Claims (1)

[Claims] 1. In an automatic exposure control method according to the average transmission density of each primary color in the color negative film to be printed, the first reference exposure amount is set in advance during a transition period until the second reference exposure amount corresponding to the constant exposure amount is reached. , storing the exposure amount of each primary color at the instant when any one of the three primary color exposure amounts of blue (B), green (G), and red (R), which increases with the start of exposure, reaches the second reference exposure amount; (1) For color negative films shot with a light source that deviates from the specified color temperature, the average of the first, second, and third stored exposure amounts for the color with the highest stored exposure amount. The value obtained by subtracting the value multiplied by an appropriate multiplier, or the value obtained by subtracting the average value of the first, second, and third stored exposure amounts from the first standard exposure amount multiplied by an appropriate multiplier. Reduce the exposure amount by subtracting from the second standard exposure amount, and for the other two colors, multiply the value obtained by subtracting the stored exposure amount of that color from the first standard exposure amount by an appropriate multiplier. , the correction level of the color printer is changed by increasing the exposure amount by adding it to the second standard exposure amount, and (2) for the color negative film in the color subdivision area, the first storage exposure amount is added to the second standard exposure amount. For large colors, the value obtained by subtracting the average value of the second and third stored exposure amounts from the first reference exposure amount and multiplying it by an appropriate multiplier, or the first and second reference exposure amounts from the first reference exposure amount.
The exposure amount is increased by adding the value obtained by subtracting the average value of the 2nd and 3rd stored exposure amounts and multiplying it by an appropriate multiplier to the 2nd standard exposure amount. The correction level of the color printer is changed by subtracting the value obtained by subtracting the stored exposure amount of that color from the first reference exposure amount and multiplying it by an appropriate multiplier from the second reference exposure amount to reduce the exposure amount. A color printer correction level changing method characterized by: