Samyang lens OM fit 361962 tested, 18 - 28mm f/4 - 4.5    Tested February 1992.

Lens number 361962                  

Available mounts: Canon, Minolta, Nikon, Olympus, Pentax KA, Pentax Universal screw, Ricoh PK, and Yashica/Contax.

Price: $279

Accessories: None

Specifications: (Tested values in italics)
Focal length: 18 - 28 mm (17.81 - 25.69mm)
Maximum aperture: f/4 - 4.5 (f/4.05 - 4.40)
Construction: 14 elements in 11 groups
View angle: Diag. 100º - 75º, Horiz. 90º - 65º, Vert. 67º - 46º
Minimum aperture: f/22
Click stops: ½ stops from f/4 to f/16, full stops from f/16 to f/22
Number of blades: 6
Scales: Focussing in feet (red) and meters (white). Marks for 18-, 24-, and 28mm
Zooming: 50º clockwise to 28mm
Focussing: 125º clockwise from infinity to close focus, 1 ft. 7 11/16 in. ( 0.5m)
Weight: 1 lb 13/16 oz. (477g)


Distortion: @ 18mm, 2.1% barrel; @ 24mm, 2.4% barrel; @ 28 mm, 1.8% barrel.
Lateral color: Negligible at 18mm, slight at 24mm, moderate at 28mm - may affect picture quality.

Hands on: Somewhat longish physical length and large front-lens elements reflect remarkable zoom focal length range. Well finished in bright black. All markings large and highly legible. No infra-red focus marking or depth-of-field scale. Rubberised and highly grippable zoom and focussing rings turn smoothly. Metal ribbed aperture ring of good size.

In the lab. SQF data indicates performance as average at 18mm and 24mm settings but below average at all focal lengths.

In the field: Test slides were generally well exposed, with good contrast but with noticeable edge and corner light falloff from maximum aperture to f/8 at 18mm, f/9.5 at 24mm, and f/11 at 28mm. Flare was very well controlled throughout.

Conclusion: Extreme wide-angle but relatively compact zooms are among the most difficult lenses to design and manufacture. Obviously, sacrifices such as in maximum aperture light falloff, field curvature, and SQF results at 28mm are trade-offs for the high convenience of the focal length selection available.

Macro / Close-Focussing

Max MAG: (all distances to lens)
1:22 @ 18mm ( 1 ft 2 in. (0.36 m)
1:15 @ 28mm (1 ft. 3 in. (0.38m)

@ 18mm: Sharpness above average from centre to corner at all f-stops. Excessive barrel distortion.
@ 28mm: Sharpness above average in certre at all f-stops, acceptable in corners only from f/16 to f/22. Little noticeable barrel distortion.
Subjective Quality Factor     KEY:
A+
A
B+
B
C+
C
D
F


@18mm

MAG   >
4
5
6
8
12
17
22
Size (in.)   >
3.5 x 5
4 x 6
5 x 7
8 x 10
11 x 14
16 x 20
20 x 24
@ f/4.0
97.4
95.9
94.2
90.1
79.9
65.7
52.5
@ f/4.5(5.6?)
98.2
97.1
95.9
92.9
85.2
73.8
62.0
@ f/8
99.2
98.8
98.2
96.9
93.1
87.0
79.8
@ f/11.0
99.3
98.9
98.4
97.2
93.9
88.4
81.8
@ f/16.0
99.3
98.9
98.4
97.1
93.8
88.1
81.4
@ f/22.0
98.2
97.1
95.9
93.0
85.3
73.8
62.1


@24mm

MAG   >
4
5
6
8
12
17
22
Size (in.)   >
3.5 x 5
4 x 6
5 x 7
8 x 10
11 x 14
16 x 20
20 x 24
@ f/4.0
97.2
95.7
93.9
89.6
79.1
64.6
51.2
@ f/5.6
97.1
95.5
93.6
89.1
78.1
63.3
49.7
@ f/8
97.9
96.7
95.3
92.0
83.4
70.9
58.6
@ f/11.0
99.1
98.5
97.9
96.3
92.0
84.9
76.8
@ f/16.0
99.2
98.7
98.2
96.8
92.9
86.6
79.3
@ f/22.0
98.9
98.3
97.6
95.8
90.9
83.0
74.2


@28mm

MAG   >
4
5
6
8
12
17
22
Size (in.)   >
3.5 x 5
4 x 6
5 x 7
8 x 10
11 x 14
16 x 20
20 x 24
@ f/4.0
96.3
94.3
91.9
86.4
73.4
56.9
42.9
@ f/5.6
96.2
94.2
91.8
86.2
73.0
56.4
42.4
@ f/8
97.4
96.0
94.3
90.3
80.2
66.2
53.0
@ f/11.0
98.4
97.5
96.5
93.4
87.0
76.6
65.6
@ f/16.0
98.8
98.2
97.4
95.5
90.3
82.0
72.8
@ f/22.0
98.9
98.3
97.5
95.7
90.8
82.8
73.9


SQF testing

This is some of what Pop Photo had to say about SQF testing in November 1990 when they were finally happy with their system.

In short, SQF is the way to relate the total of all our MTF measurements to the quality you can expect at any given print size.

Under normal conditions, a slight difference in SQF will hardly be noticeable. Experimentally, it's been shown that a difference of 10 SQF units will show a definite difference in quality level, with a difference of only 5 units producing a just noticeable difference (JND). SQFs below 50 yield unacceptable results.

SQF: making the grade
With five distinct quality levels to work with, it seeemed only natural to assign letter grades to each:   A for the best, then B, C, D, and finally F for anything below 50. We added "+" grades to A - C to characterize the quality, widening the group as quality diminished, giving a full 10 units to both C and C+ grades. In our system, we broke them down this way:
99.9 - 95.0   A+
94.9 - 90.0   A  
89.9 - 85.0   B+
84.9 - 80.0   B  
79.9 - 70.0   C+
69.9 - 60.0   C  
59.9 - 49.5   D  
          <49.5 F  

We expanded the C and C+ categories to fit actual experience. There was little point distinguishing between a D and D+. As overall quality goes down, it is increasingly difficult to distinguish between pictures. It's easier to tell which of two good prints is sharper than it is to determine which of two prints is fuzzier.

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