“雅”頭片子平民蔡司 Yashica Auto Yashinon-DX 50mm f/1.7 M42 mount for pentax, canon, sony
Yashica Auto Yashinon-DX 50mm f/1.7 -- Mount: M42
japan Tomioka factory
Aperture Max: F1.7
Aperture Min: F16
Focal Length: 50mm
Diaphragm blades: 6
Auto/Manual Switch
6 elements in 5 groups
Filter Size: 52mm
Minimum Focus: 50 cm
Weight: 230 grams
Mount: M42
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Sharpness 9.0
Aberrations 8.4
Bokeh 8.8
Handling 9.8
Value 9.6

please read the link
http://www.pentaxforums.com/userreviews/yashica-auto-yashinon-dx-50mm-f-1-7.html#ixzz4Wt8KfLrA
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Yashica Auto Yashinon DX 50 mm f/ 1.7 - fast prime standard lens for a 35mm SLR with M42 screw mount.
Mechanical quality 5.00 5
Optical quality 4.60 5
Usability 4.40 5
Pricing / Value 4.80 5
Bokeh 4.80 5
Overall lens rating 4.72

please read the link
http://allphotolenses.com/lenses/item/c_1994.html
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someone call “雅”頭片子平民蔡司
http://www.soupis.com/thread-131336-1-1.html
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Without lens cap