JP4986710B2 - Wide angle macro lens system - Google Patents

Description

  The present invention relates to a wide-angle macro lens system used for a photographic camera and a video camera.

  In the field of products such as photographic cameras and video cameras, the macro lens system is known as a lens that can shoot objects placed at close distances with a shooting magnification of 0.5x to 1x and higher with good image quality. It has been. Most of the macro lens systems provided in the field of photographic camera products are used not only for short-distance shooting but also for aberration correction over the entire range from infinity to medium distance to short distance.

  In general, a lens that is mounted on a photographic camera is designed with emphasis on aberration correction at infinity, so it maintains good aberration correction from infinity to long distances, but aberration fluctuations are large at short distances. Therefore, the image quality is usually deteriorated to some extent. On the other hand, the macro lens system is designed in consideration of being able to shoot at a short distance, and therefore, many of them can suppress aberration fluctuations in short distance shooting and obtain a good image quality.

For example, in Japanese Patent Laid-Open No. 2005-189727, it is composed of two groups, positive and negative, and the aberration variation is suppressed by moving the first group and the second group to the object side during focusing from infinity to a close object. Macro lens systems have been proposed. Japanese Patent Application Laid-Open No. 2004-212692 proposes a macro lens system having the same configuration and suppressing aberration fluctuations at a short distance. Japanese Patent Laid-Open No. 9-211319 is composed of four groups of positive, negative, positive and positive in order from the object side. When focusing from infinity to a short distance, the first group and the fourth group are fixed, and the second group is moved to the image side. A macro lens system in which aberration variation is suppressed by moving the third group to the object side has been proposed. In Japanese Patent Laid-Open No. 2003-185916, there are three positive and negative groups in order from the object side, and when focusing from infinity to short distance, the first and second groups are moved out to the object side while the third group is fixed. At the same time, a proposal has been made to correct the aberration by making a U-turn on the final positive lens of the second group.
JP 2005-189727 A JP 2004-212692 JP Japanese Patent Laid-Open No. 9-211319 Japanese Patent Laid-Open No. 2003-185916

  Although these macro lens systems correct aberrations during close-up shooting, large spherical aberrations occur due to large spherical aberration on the under side or large higher-order spherical aberration on the over side. Spherical aberration occurs. For this reason, the balance between the best image plane position defined by the spherical aberration and the best image plane position defined by the curvature of field is lost, and it cannot be said that the correction of aberrations particularly at the time of close-up shooting is sufficient. Further, depending on the proposal, there are a large number of moving lens groups, which causes problems such as a complicated moving mechanism and disadvantages in size and weight compared to a lens having a small number of moving groups.

  Furthermore, when the shortest shooting distance is shortened (higher magnification), this phenomenon becomes remarkable, and it becomes very difficult to correct aberrations. Further, if a countermeasure is taken by increasing the number of lens movement groups in order to increase the degree of freedom of aberration correction, the weight and dimensions of the lens will increase, resulting in a lack of portability.

  The present invention is a wide-angle macrolens system having an angle of view of about 42 to 43 °, in which aberrations are sufficiently corrected over a wide range of shooting distances from infinity to high-magnification close-up shooting, and the moving mechanism for focusing can be simplified. The purpose is to obtain.

The wide-angle macro lens system according to the present invention includes, in order from the object side, a front group and a rear group whose intervals change during focusing, and the front group includes a first sub group positioned on the object side with an aperture interposed therebetween and an image side. The first sub group includes at least a negative meniscus lens having a convex surface directed toward the object side and a strong concave surface positioned closest to the diaphragm side. A negative lens facing the diaphragm, and a positive lens positioned between the two negative lenses, and the second sub-group has a lens facing the concave surface on the diaphragm side as the lens closest to the diaphragm; The rear group is composed of, in order from the object side, a negative lens having a strong concave surface directed to the image side and a biconvex lens, and satisfies the following conditional expressions (1) and (2).
(1) -0.52 <f1 / f1a <-0.20
(2) -0.35 <f2 / f1a <-0.20
However,
f1: the focal length of the negative meniscus lens closest to the object side in the first sub group,
f2: Focal length of the negative lens closest to the stop in the first sub group,
f1a: the composite focal length of the first subgroup,
It is.

The wide-angle macro lens system of the present invention preferably satisfies the following conditional expression (3).
(3) 2.66 <f1a / f <7.00
However,
f: Focal length when focusing on an object at infinity of the entire system,
It is.

  Moreover, it is preferable that the following conditional expression (4) is satisfied.

(4) 0.00 ≦ dG2 / dG1 <0.32.
However,
dG1; the amount of movement of the front group when the front group moves from the infinite object focusing position to the same magnification photographing position;
dG2: the amount of movement of the rear group when the rear group moves from the infinite object focusing position to the same magnification photographing position;
It is.
The value of dG2 / dG1 in the conditional expression (4) may take a constant value or change in the conditional expression when focusing on each shooting distance between an object at infinity and a short distance object.

  The wide-angle macro lens system of the present invention has a mode in which the front group and the rear group are individually moved (with independent trajectories) to the object side when focusing from an object at infinity to a short distance object, and the rear group is fixed. Any of the modes in which only the front group is moved to the object side is possible, but the latter which can simplify the focus adjustment mechanism is preferable.

  According to the present invention, a wide-angle macro having an angle of view of about 42 to 43 °, in which aberrations are sufficiently corrected over a wide range of shooting distances from infinity to high-magnification short-distance shooting and the moving mechanism for focusing can be simplified. A lens system can be obtained.

  The basic structure of the wide-angle macro lens system according to the present invention will be described. The wide-angle macro lens system according to the present invention is shown in FIGS. 1 (FIG. 3), 5 (FIG. 7), FIG. 9 (FIG. 11), FIG. 13 (FIG. 15), FIG. 17 (FIG. 19), and FIG. As shown in the respective embodiments, the front group G1 having a positive refractive power and the rear group G2 having a negative refractive power are arranged in order from the object side. The front group G1 and the rear group G2 are divided by a portion where the interval changes during focusing from an infinitely distant object to a close object. The front group G1 includes a first sub group G1a located on the object side with the aperture S interposed therebetween, and a second sub group G1b located on the image side. The first sub group G1a has a convex surface in order from the object side. A negative meniscus lens 11 directed to the side, two positive lenses 12 and 13, and a negative lens 14 having a strong concave surface directed to the stop. The second sub group G1b includes a negative lens having a concave surface on the aperture side, on the most object side. The rear group G2 includes, in order from the object side, a negative lens having a strong concave surface facing the image side and a biconvex lens. I is the image plane.

  Regarding the lens configuration of the second sub group G1b, it is important that the lens closest to the diaphragm S side has a concave surface on the diaphragm S side, and there is a degree of freedom for other configurations.

  In the wide-angle macro lens system according to the present invention, first, a gauss type having a symmetric structure centered on the stop is used as a master lens (from the third lens to the eighth lens) to sufficiently correct various aberrations. Moreover, in order to obtain a sufficient back focus with a wide-angle type, a retro focus configuration in which a negative lens is arranged in front of the master lens is adopted. In addition, the rear group G2 is arranged to satisfactorily correct off-axis aberrations when focusing on a short-distance object. When focusing from an object at infinity to an object at a short distance, both the front group G1 and the rear group G2 are moved to the object side (floating) or the rear group G2 is fixed, and only the front group G1 is moved to the object side. Embodiments are possible. The first sub group G1a and the second sub group G1b are not moved relative to each other (the interval is not changed).

  Conditional expressions (1) and (2) are conditions for realizing good spherical aberration correction particularly in close-up photography. If the lower limit of conditional expression (1) is not reached, high-order spherical aberration will occur, and spherical aberration toward the under side will occur greatly, resulting in insufficient correction. If the upper limit of conditional expression (1) is exceeded, high-order spherical aberration having the opposite sign will occur, and large spherical aberration will occur on the over side. It also causes annular spherical aberration. If the lower limit of conditional expression (2) is not reached, high-order spherical aberration occurs and spherical aberration toward the under side occurs, resulting in insufficient correction. If the upper limit of conditional expression (2) is exceeded, spherical aberration correction will be over (overcorrection).

  Conditional expression (3) is a condition for correcting spherical aberration more satisfactorily during close-up photography. If the lower limit of conditional expression (3) is not reached, high-order spherical aberration occurs and spherical aberration toward the under side occurs, resulting in insufficient correction. If the upper limit of conditional expression (3) is exceeded, higher-order spherical aberration having the opposite sign is generated, and spherical aberration correction is over (overcorrection). It also causes annular spherical aberration.

  The wide-angle macro lens system of the present invention satisfies the above-described lens configuration and conditional expressions, so that excessive spherical aberration occurs in the first sub group, particularly the lens closest to the object side and the lens immediately before the stop, particularly at close-up shooting. The generation of high-order aberrations can be suppressed. Furthermore, the aberration generated in the first sub group can be efficiently corrected by the second sub group immediately after. For this reason, it is possible to suppress the occurrence of annular spherical aberration due to large bulging of the spherical aberration to the under side and large high-order aberration to the over side, and at the same time, the best image plane position defined by the spherical aberration and the image plane A balance with the best image plane position defined by the curvature can be achieved, and a good aberration correction state can be maintained even when photographing a short distance object. For example, in Japanese Patent Laid-Open No. 2005-189727 (Patent Document 1), on the other hand, spherical aberration including a very large high-order aberration occurs in the lens closest to the object side and the lens immediately before the stop, and this is corrected by the lens system immediately after that. Since the aperture is not completely closed, the spherical aberration is greatly generated on the over side in the region where the aperture is large, and a large annular spherical aberration is generated in the middle of the aperture.

  Conditional expression (4) defines favorable correction conditions for off-axis aberrations, particularly field curvature and distortion. If the lower limit of conditional expression (4) is not reached, the image surface swells to the under side, the balance with the best image surface defined by spherical aberration is lost, and barrel distortion increases. On the contrary, when the upper limit of conditional expression (4) is exceeded, the image surface swells to the over side, and similarly the balance with spherical aberration is lost, and the pincushion distortion becomes large.

Next, specific numerical examples will be shown. In the various aberration diagrams and tables, SA in the chromatic aberration (axial chromatic aberration) diagram and lateral chromatic aberration diagram represented by spherical aberration, SC is spherical aberration, SC is a sine condition, d-line, g-line, and C-line are aberrations for each wavelength. S is sagittal, M is meridional, F _NO. Is F number, FE is effective F number, Y is image height, f is the focal length of the whole system, W is half angle of view (°), fB Is the back focus, r is the radius of curvature, d is the lens thickness or lens interval, N _d is the refractive index of the d-line, and ν is the Abbe number. None of the examples employs an aspherical surface.

[Numerical Example 1]
1 to 4 and Table 1 show Numerical Example 1 of the wide-angle macro lens system of the present invention. FIGS. 1 and 3 are lens configuration diagrams when the object is focused at infinity and when the object is focused at the shortest (shooting distance) (shooting magnification 1.5 times), respectively, and FIGS. 2 and 4 are FIGS. The aberration diagrams in the lens configuration of No. 3, Table 1 shows the numerical data.

  The front group G1 (surface Nos. 1 to 15) having a positive refractive power is from the first sub group G1a (surface Nos. 1 to 8), the stop S, and the second sub group G1b (surfaces No. 9 to 15). The first sub group G1a is composed of, in order from the object side, a negative meniscus lens 11 having a convex surface directed toward the object side, two positive lenses 12 and 13, and a negative lens 14 having a strong concave surface directed toward the stop. ing. The second sub group G1b includes a cemented lens of a biconcave negative lens with a concave surface facing the object side and a biconvex positive lens, a positive meniscus lens convex on the image side, and a biconvex positive lens. The rear group G2 (surface Nos. 16 to 19) includes, in order from the object side, a negative meniscus lens and a biconvex lens with a strong concave surface facing the image side. The stop S is located 3.71 in front (object side) of the lens (9th surface) closest to the stop S in the second sub group G1b. Focusing from an infinitely distant object to a close object is performed by moving the front group G1 and the rear group G2 individually (independently) to the object side.

(Table 1)
F _NO. = 1: 2.8
f = 36.80
W = 21.2
fB = 38.00
Surface No. rd Nd ν
1 82.874 1.00 1.60311 60.7
2 21.568 14.29
3 12630.355 2.64 1.85026 32.3
4 -74.391 9.46
5 27.210 3.64 1.72916 54.7
6 -69.778 1.79
7 -126.381 3.09 1.59270 35.3
8 22.892 13.03
9 -13.875 1.00 1.64831 33.8
10 81.886 5.14 1.49700 81.6
11 -16.524 0.20
12 -213.597 2.03 1.78800 47.4
13 -52.972 0.10
14 62.934 2.83 1.78800 47.4
15 -101.253 D15
16 367.414 1.30 1.69350 53.2
17 34.066 2.17
18 89.571 2.55 1.60323 42.3
19 -84.763-

Magnification D15 fB
0.0 1.20 38.00
-1.5 28.54 51.67

[Numerical Example 2]
5 to 8 and Table 2 show Numerical Example 2 of the wide-angle macro lens system of the present invention. FIG. 5 and FIG. 7 are lens configuration diagrams at the time of focusing on the object at infinity and the shortest (shooting distance) object focusing (shooting magnification of 1.5 times), respectively, and FIGS. 6 and 8 are FIG. 5 and FIG. FIG. 7 shows various aberrations in the lens configuration, and Table 2 shows numerical data. The basic lens configuration is the same as in Numerical Example 1, but the rear group G2 is fixed during focusing. The stop S is at a position 4.84 in front (object side) of the lens (9th surface) closest to the stop S in the second sub group G1b.
(Table 2)
F _NO. = 1: 2.8
f = 36.80
W = 21.1
fB = 38.01
Surface No. rd Nd ν
1 162.211 2.00 1.60710 59.8
2 25.590 19.96
3 139.453 4.93 1.85000 35.3
4 -86.212 7.00
5 29.996 3.43 1.70224 57.4
6 -84.482 2.03
7 -86.003 1.00 1.59270 35.3
8 25.842 13.99
9 -17.203 1.00 1.66928 31.5
10 92.973 4.33 1.49700 81.6
11 -21.296 0.20
12 -123.919 2.22 1.79999 48.6
13 -35.308 0.10
14 81.173 3.15 1.80000 46.2
15 -109.471 D15
16 -113.185 2.19 1.69350 53.2
17 38.116 1.98
18 106.814 2.95 1.60323 42.3
19 -46.589-

Magnification D15 fB
0.0 1.43 38.01
-1.5 36.37 38.01

[Numerical Example 3]
9 to 12 and Table 3 show Numerical Example 3 of the wide-angle macro lens system of the present invention. FIGS. 9 and 11 are lens configuration diagrams when focusing on an object at infinity and when focusing on the shortest (shooting distance) object (shooting magnification 1.5 times), respectively, and FIGS. 10 and 12 are FIGS. FIG. 11 is a diagram showing various aberrations in the lens configuration, and Table 3 shows numerical data. The basic lens configuration and focusing mode are the same as those in Numerical Example 1. The stop S is at a position 2.33 in front (object side) of the lens (9th surface) closest to the stop S in the second sub group G1b.
(Table 3)
F _NO. = 1: 2.8
f = 36.79
W = 21.2
fB = 37.99
Surface No. rd Nd ν
1 115.618 2.00 1.67903 55.6
2 26.558 20.74
3 84.786 4.00 1.81790 45.4
4 -188.991 3.29
5 36.547 3.27 1.79446 49.5
6 -165.274 6.41
7 -101.142 0.68 1.59270 35.3
8 27.092 8.79
9 -17.882 1.00 1.76375 31.1
10 105.883 3.24 1.49700 81.6
11 -19.395 0.20
12 -77.677 2.11 1.80000 48.6
13 -32.091 0.10
14 53.548 2.81 1.80000 48.5
15 -87.068 D15
16 -77.015 1.96 1.69350 53.2
17 39.317 2.06
18 147.026 3.13 1.60323 42.3
19 -37.007-

Magnification D15 fB
0.0 1.49 37.99
-1.5 27.48 49.28

[Numerical Example 4]
13 to 16 and Table 4 show Numerical Example 4 of the wide-angle macro lens system of the present invention. FIGS. 13 and 15 are lens configuration diagrams when the object is focused at infinity and when the object is focused at the shortest (shooting distance) (shooting magnification of 1.5 times), respectively, and FIGS. 14 and 16 are FIGS. Various aberration diagrams in the lens configuration of FIG. 15, Table 4 shows numerical data thereof. The basic lens configuration and focusing mode are the same as those in Numerical Example 1. The stop S is located at a position 2.65 in front (object side) of the lens (9th surface) closest to the stop S in the second sub group G1b.
(Table 4)
F _NO. = 1: 2.8
f = 37.02
W = 21.1
fB = 38.05
Surface No. rd Nd ν
1 173.123 1.96 1.70172 54.5
2 30.706 19.32
3 74.802 4.80 1.75400 43.1
4 -194.375 0.20
5 55.813 5.08 1.74188 53.4
6 -208.078 12.63
7 439.700 1.30 1.59270 35.3
8 28.732 4.13
9 -14.624 1.00 1.70916 30.1
10 91.846 3.52 1.49700 81.6
11 -19.374 0.20
12 -53.972 2.39 1.80000 48.6
13 -25.952 0.10
14 52.892 3.51 1.80000 48.5
15 -59.788 D15
16 -76.008 1.81 1.69350 53.2
17 39.914 2.28
18 161.892 3.47 1.60323 42.3
19 -36.858-

Magnification D15 fB
0.0 1.20 38.05
-1.5 26.71 49.76

[Numerical Example 5]
17 to 20 and Table 5 show Numerical Example 5 of the wide-angle macro lens system of the present invention. FIGS. 17 and 19 are lens configuration diagrams at the time of focusing on the object at infinity and the shortest (shooting distance) of the object (shooting magnification of 1.5 times), respectively, and FIGS. 18 and 20 are FIGS. FIG. 19 shows various aberrations in the lens configuration, and Table 5 shows numerical data. The basic lens configuration and focusing mode are the same as those in Numerical Example 1. The stop S is at a position 2.69 in front (object side) of the lens (9th surface) closest to the stop S in the second sub group G1b.
(Table 5)
F _NO. = 1: 2.8
f = 36.96
W = 21.1
fB = 37.98
Surface No. rd Nd ν
1 275.037 1.89 1.65721 56.7
2 30.851 19.99
3 99.398 5.37 1.77031 45.9
4 -174.563 0.20
5 49.360 2.96 1.72271 55.2
6 -187.468 14.12
7 2150.464 1.30 1.59270 35.3
8 30.500 4.14
9 -14.570 1.00 1.69731 30.7
10 168.737 3.70 1.49700 81.6
11 -16.869 0.20
12 -62.219 2.14 1.80000 48.6
13 -30.986 0.10
14 51.585 3.29 1.80000 48.5
15 -71.881 D15
16 -67.717 1.43 1.69350 53.2
17 40.189 2.21
18 154.526 3.52 1.60323 42.3
19 -35.387-

Magnification D15 fB
0.0 1.20 37.98
-1.5 26.63 49.66

[Numerical Example 6]
21 to 24 and Table 6 show Numerical Example 6 of the wide-angle macro lens system of the present invention. FIGS. 21 and 23 are lens configuration diagrams when focusing on an object at infinity and when focusing on the shortest (shooting distance) object (shooting magnification of 1.5 times), respectively, and FIGS. 21 and 23 are FIGS. FIG. 23 shows various aberrations in the lens configuration of FIG. 23, and Table 6 shows numerical data. The basic lens configuration and focusing mode are the same as those in Numerical Example 1. The stop S is at a position 2.59 in front (object side) of the lens (9th surface) closest to the stop S in the second sub group G1b.
(Table 6)
F _NO. = 1: 2.8
f = 36.80
W = 21.2
fB = 37.99
Surface No. rd Nd ν
1 158.774 1.00 1.50029 70.5
2 22.009 17.63
3 377.873 3.81 1.85000 33.9
4 -69.331 10.29
5 32.098 4.44 1.60000 74.8
6 -47.501 2.11
7 -63.103 6.25 1.59270 35.3
8 29.744 6.69
9 -15.353 1.12 1.68301 35.0
10 100.236 4.10 1.49700 81.6
11 -17.558 0.20
12 -74.499 2.05 1.80000 48.6
13 -34.359 0.10
14 52.112 2.72 1.80000 46.2
15 -134.793 D15
16 -108.301 1.30 1.69350 53.2
17 37.441 2.05
18 112.429 3.04 1.60323 42.3
19 -44.053-

Magnification D15 fB
0.0 1.20 37.99
-1.5 30.41 45.62

Table 7 shows values for the conditional expressions of the numerical examples.
(Table 7)
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
Conditional expression (1) -0.46 -0.51 -0.33 -0.21 -0.23 -0.48
Conditional expression (2) -0.31 -0.34 -0.24 -0.20 -0.23 -0.32
Conditional expression (3) 2.87 2.66 4.13 6.95 6.25 2.90
Conditional expression (4) 0.19 0.00 0.30 0.31 0.31 0.21

  As apparent from Table 7, Examples 1 to 6 satisfy the conditional expressions (1) to (4), and various aberrations are relatively well corrected as is apparent from the various aberration diagrams. In particular, various aberrations are well corrected at the shortest shooting distance (-1.5 times).

It is a lens block diagram at the time of infinity object focusing of Numerical Example 1 of the wide angle macro lens system by this invention. FIG. 2 is a diagram illustrating various aberrations of the lens configuration in FIG. 1. FIG. 3 is a lens configuration diagram in the shortest object in-focus state in Numerical Example 1. FIG. 4 is a diagram illustrating various aberrations in the lens configuration in FIG. 3. It is a lens block diagram at the time of infinity object focusing of Numerical Example 2 of the wide angle macro lens system by this invention. FIG. 6 is a diagram illustrating various aberrations of the lens configuration in FIG. 5. It is a lens block diagram in the shortest object focusing state of Numerical Example 2. FIG. 8 is a diagram illustrating various aberrations in the lens configuration in FIG. 7. It is a lens block diagram at the time of infinity object focusing of numerical Example 3 of the wide angle macro lens system by this invention. FIG. 10 is a diagram illustrating various aberrations of the lens configuration in FIG. 9. It is a lens block diagram in the shortest object focusing state of Numerical Example 3. FIG. 12 is a diagram illustrating various aberrations in the lens configuration in FIG. 11. It is a lens block diagram at the time of infinity object focusing of Numerical Example 4 of the wide angle macro lens system by this invention. FIG. 14 is a diagram illustrating various aberrations of the lens configuration in FIG. 13. FIG. 9 is a lens configuration diagram in a shortest object in-focus state according to Numerical Example 4. FIG. 16 is a diagram illustrating various aberrations in the lens configuration in FIG. 15. It is a lens block diagram at the time of infinity object focusing of Numerical Example 5 of the wide angle macro lens system by this invention. FIG. 18 is a diagram illustrating various aberrations of the lens configuration in FIG. 17. FIG. 9 is a lens configuration diagram in a shortest object in-focus state according to Numerical Example 5. FIG. 20 is a diagram illustrating various aberrations in the lens configuration in FIG. 19. It is a lens block diagram at the time of infinity object focusing of Numerical Example 6 of the wide angle macro lens system by this invention. FIG. 22 is a diagram illustrating various aberrations of the lens configuration in FIG. 21. FIG. 10 is a lens configuration diagram of Numerical Example 6 in the shortest object in-focus state. FIG. 24 is a diagram illustrating various aberrations in the lens configuration in FIG. 23.

Claims (4)

In order from the object side, it consists of a front group and a rear group whose intervals change during focusing,
The front group includes a first sub group located on the object side and a second sub group located on the image side across the stop,
The first sub group includes a negative meniscus lens that is located closest to the object and having a convex surface directed toward the object side, a negative lens that is located closest to the diaphragm and has a strong concave surface directed toward the stop, and a space between the two negative lenses. At least a positive lens located at
The second sub group has a lens with a concave surface facing the diaphragm side as the lens on the most diaphragm side,
The rear group, in order from the object side, is composed of two lenses, a negative lens and a biconvex lens with a strong concave surface facing the image side,
A wide-angle macro lens system satisfying the following conditional expressions (1) and (2):
(1) -0.52 <f1 / f1a <-0.20
(2) -0.35 <f2 / f1a <-0.20
However,
f1: the focal length of the negative meniscus lens closest to the object side in the first sub group,
f2: Focal length of the negative lens closest to the stop in the first sub group,
f1a: Composite focal length of the first subgroup. 2. The wide-angle macro lens system according to claim 1, wherein the wide-angle macro lens system satisfies the following conditional expression (3).
(3) 2.66 <f1a / f <7.00
However,
f: Focal length when focusing on an object at infinity of the entire system. 3. The wide-angle macro lens system according to claim 1, wherein the wide-angle macro lens system satisfies the following conditional expression (4).
(4) 0.00 ≦ dG2 / dG1 <0.32.
However,
dG1; the amount of movement of the front group when the front group moves from the infinite object focusing position to the same magnification photographing position;
dG2: The amount of movement of the rear group when the rear group moves from the object focusing position at infinity to the same magnification photographing position. 4. The wide-angle macro lens system according to claim 1, wherein only the front group is moved when focusing from an object at infinity to a short-distance object.

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