Olympus OM system close-up and macro equipment

Zuiko Auto-Macro Lens 20mm f/2

Introduction

This is one of the second generation of bellows macro lenses for the Olympus OM system and was first produced around 1980. Like the other second-generation lenses, this one has an automatic diaphragm and a focusing helicoid to assist fine focusing. Olympus was the first manufacturer to introduce high-magnification macro lenses with automatic diaphragms.

The lens is designed for magnifications between 4.2× and 16×. It has the standard OM bayonet, and when used with the Telescopic Auto Tube 65–116, the available magnifications range from 6.8× to 9.5×. When used with the Auto Bellows, the available magnifications range from 5.3× to 13.6×; the Double Cable Release is needed to close the diaphragm. It can also be used with the Auto Extension Tubes.

The short working distance (18–20 mm) can make it difficult to light the subject, and so the front part of lens is tapered and stepped to help prevent the lens from blocking the light.

It has a 49mm filter mount set back from the front of the lens (so you cannot use it for filters) that is used for the special screw-in lens cap, and to which you can attach the T10 Ring Flash 1 and the mounting ring for the T-28 Macro Flash 1. The T8 Ring Flash 2 is not suitable, because of the short working distance of this lens.

This lens was introduced around 1980 and replaced the Zuiko Macro 20mm f/3.5 lens, which was slower, had a manual diaphragm, and had an RMS screw thread instead of the standard OM bayonet.

Version

  1.  ZUIKO AUTO-MACRO 20mm 1:2  (101xxx, 102xxx, 103xxx)

Features

Optimum range ×4.2 – ×16
Working distance 18–20 mm
Lens elements 6
Lens groups 4
Lens coating Multicoated
Iris diaphragm Automatic
Iris blades 6
Maximum aperture f/2
Minimum aperture f/16
Pupil ratio (exit/entry) 0.75
Focusing helicoid 3.8 mm
Minimum length 46 mm, 1.8 in
Maximum diameter 60 mm, 2.4 in
Weight 170 g, 6.0 oz
Mount OM bayonet
Focusing screens 1-11, 1-12
Front cap Special 49 × 0.75 mm screw-in
(same as Auto Macro 38mm f/2.8)
Rear cap Standard OM
Case Lens Pouch 100N
Hood None
Filter size 21 mm (slide-on)
US catalog no. 103-701
Introduced 1985 ?
Discontinued 2002
Zuiko Auto-Macro Lens 20 mm f/2
Zuiko Auto-Macro Lens 20 mm f/2


Cross-section
Cross-section


Lens cap
Screw-in lens cap

Magnification range with Auto Bellows

Lowest magnification ×5.3 Subject area ?×? mm Working distance 20 mm
Highest magnification ×13.5 Subject area ?×? mm Working distance 18 mm

Magnification range with Telescopic Auto Tube 65–116

Lowest magnification ×6.3 Subject area ?×? mm Working distance 19 mm
Highest magnification ×9.2 Subject area ?×? mm Working distance 18 mm

Accessories

A Lieberkühn Reflector and a Mirror Housing were made to fit this lens.

Self-adhesive labels were provided with the T Power Control 1 to stick onto a Calculator Panel to provide readings for manual flash with the T10 Ring Flash 1 and T28 Macro Single Flash 1.

The Macro Flash Shoe Ring screws into the 49 mm filter mount, and takes the heads of the T28 Macro Twin Flash 1 or the T28 Macro Single Flash 1.

See also:    Close-up and Macro Photography – Bellows Macro Lenses

Going digital

When the Zuiko Auto-Macro 20mm f/2 is mounted on the Auto Bellows attached to a digital body, the only ways to close down the iris diaphragm are to use the cable release socket or the stop down lever on the lens mount of the bellows. When it is mounted on the Telescopic Auto Tube, OM/EOS and OM/Four Thirds adapters change the automatic diaphragm to manual click stops.

The following tables are based on those in the instruction leaflet, with adjustments for different sensor sizes and for any additional extension needed to allow the release lever on the rear of the bellows to clear an overhanging pentaprism or flash.

Magnification table for Auto Bellows with Canon EOS 5D MkII

36×24 mm sensor, with 7 mm extension tube between bellows and OM/EOS adapter

Magnification 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
Subject area (mm) 6.0 × 4.0 5.1 × 3.4 4.5 × 3.0 4 × 2.7 3.6 × 2.4 3.3 × 2.2 3.0 × 2.0 2.7 × 1.8
Bellows scale* (mm) 76 96 116 136 156 176 196 216
Lens to subject distance (mm) 20 19 19 19 18 18 18 18

Magnification table for Auto Bellows with Canon EOS 40D

22.2×14.8 mm APS-C sensor, with 14 mm extension tube between bellows and OM/EOS adapter

Magnification 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
Subject area (mm) 3.7 × 2.5 3.2 × 2.1 2.8 × 1.85 2.5 × 1.6 2.2 × 1.5 2.0 × 1.3 1.85 × 1.2 1.7 × 1.1
Bellows scale* (mm) 69 89 109 129 149 169 189 209
Lens to subject distance (mm) 20 19 19 19 18 18 18 18

Magnification table for Auto Bellows with Olympus E-1, E-300, E-330 and Micro Four Thirds

17.3×13.0 mm Four-Thirds sensor, with no extension tube between bellows and OM/Four Thirds adapter

Magnification 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
Subject area (mm) 2.9 × 2.2 2.5 × 1.9 2.2 × 1.6 1.9 × 1.4 1.7 × 1.3 1.6 × 1.2 1.4 × 1.1 1.3 × 1.0
Bellows scale* (mm) 83 103 123 143 163 183 203 223
Lens to subject distance (mm) 20 19 19 19 18 18 18 18

Magnification table for Auto Bellows with Olympus E-3, E-410, E-500, E-510, E-620

17.3×13.0 mm Four-Thirds sensor, with 7 mm extension tube between bellows and OM/Four Thirds adapter

Magnification 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
Subject area (mm) 2.9 × 2.2 2.5 × 1.9 2.2 × 1.6 1.9 × 1.4 1.7 × 1.3 1.6 × 1.2 1.4 × 1.1 1.3 × 1.0
Bellows scale* (mm) 76 96 116 136 156 176 196 216
Lens to subject distance (mm) 20 19 19 19 18 18 18 18

* The bellows scale should be read at the rear of the body mount, with the lens mount positioned at the front end of the rail.

Magnification table for Telescopic Auto Tube 65~116 with 22.2×14.8 mm APS-C sensor

(Cameras such as Canon EOS 40D)

Magnification 7.0 8.0 9.0 10.0
Subject area (mm) 3.2 × 2.1 2.8 × 1.85 2.5 × 1.6 2.2 × 1.5
Tube length (mm) 70 90 110 116 + helicoid
Lens to subject distance (mm) 19 19 19 18

Magnification table for Telescopic Auto Tube 65~116 with 17.3×13.0 mm Four-Thirds sensor

(Cameras such as Olympus E-series and Micro Four Thirds)

Magnification 7.0 8.0 9.0 10.0
Subject area (mm) 2.5 × 1.9 2.2 × 1.6 1.9 × 1.4 1.7 × 1.3
Tube length (mm) 70 90 110 116 + helicoid
Lens to subject distance (mm) 19 19 19 18

Instruction leaflet

Reproduced with permission from the copyright owner, Olympus Optical Co., Ltd

ZUIKO AUTO-MACRO 20mm 1:2

These macro lenses feature the world’s first automatic diaphragm operation for high magnification works in conjunction with the OM System macrophoto units.

• Combinations

Varimagni Finder
or
Dioptric Correction Lens 1 + Eyecup 1
OM-2N
or
OM-1N
Focusing Screen 1-4
or
Focusing Screen 1-11
or
Focusing Screen 1-12
Auto Extension Tube 14
or
Auto Extension Tube 25
or
Telescopic Auto Extension Tube 65~116
or
Auto Bellows
or
Macrophotographic Equipment PMT-35
Macro 20mm F2

•Specifications

Focal length 20 mm
Angle of view 9° (at high magnification)
Optical construction 6 elements in 4 groups,multi-coated
Diaphragm operation Automatic
F/stop range 2 ~ 16
Minimum field size Max. 5.7 × 8.6mm (4.2×)
Min. 1.8 × 2.6mm (13.6×)
Focusing With Auto Extension Tube 15, 25, 65 ~ 116 or Auto Bellows
Fine-focusing With direct helicoid built into lens
Length 46mm (1.8 in.)
Maximum diam. 60mm (2.4 in.)
Weight 170g (6.0 oz.)

• Care and storage

Care and storage of Olympus 20 mm f/2 Zuiko Auto-Macro lens

• With Auto Bellows

Subject Area Covered (mm)   6.5 × 4.4 6 × 4 5.5 × 3.7 5.1 × 3.4 4.5 × 3.0 4 × 2.7 3.6 × 2.4 3.3 × 2.2 3.0 × 2.0 2.7 × 1.8  
Magnification   5.5 6.0 6.5 7.0 8.0 9.0 10.0 11.0 12.0 13.0  
Scale (mm) 68 73 83 93 103 123 143 163 183 203 223 231
Distance from lens to subject (cm) 2.0 2.0 2.0 1.9 1.9 1.9 1.9 1.8 1.8 1.8 1.8 1.8

• With Telescopic Auto Extension Tube 65 ~ 116

Subject Area Covered (mm)   5.1 × 3.4 4.5 × 3.0 4 × 2.7 3.6 × 2.4
Magnification   7.0 8.0 9.0 10.0
Tube length (mm) 65 70 90 110 116 + helicoid
Distance from lens to subject (cm)   1.9 1.9 1.9 1.8

• With Auto Extension Tube 14

Subject Area Covered (mm) 9 × 6 8 × 5.3
Magnification 4.0 4.5
Tube length (mm) 14 14 + helicoid
Distance from lens to subject (cm) 2.1 2.1

• With Auto Extension Tube 25

Subject Area Covered (mm) 8 × 5.3 7.2 × 4.8
Magnification 4.5 5
Tube length (mm) 25 25 + helicoid
Distance from lens to subject (cm) 2.0 2.0

OLYMPUS
OLYMPUS OPTICAL CO., LTD.
San-Ei Building, 22-2, Nishi Shinjuku 1-chome, Shinjuku-ku, Tokyo, Japan

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Created 18th May 2001   —   Updated 8th August 2011
Copyright © 2001–2011 Alan Wood

Olympus OM system close-up and macro equipment