Additional Information on
Nikkor 20mm Ultra-wideangle lenses - 20mm f/3.5

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Ai Nikkor 20mm f/3.5 ultra-wideangle lens

Towards the end of 1977, most of the Nikkor lenses being marketed by Nikon during that time have been updated with the new Ai-Spec. It was not clear whether the non-Ai 20mm f4.0 has gone through such an upgrade but from a recent image I acquired from Ebay auction, it confirmed an Ai version of the Nikkor 20mm f/4.0 did exist. The lens shown with an Ai-lens coupling and the texture for the rubberized focusing grip has a more updated modern Nikkor feel.

However, the slow f/4.0 Ai lens went through a brief spell from March, 1977 to 1978. And confirmed rumour that ciculating during that time that a new 20mm Nikkor lens might be in the pipeline - well, they were not disappointed, as late in 1978 Nikon announced availability of a revised Nikkor 20mm f/3.5 lens. This 20mm f/3.5 has an entirely different optical formula and despite with its slight improvement done to its lens speed from f/4.0 to f/3.5, it encompassed many of the good elements found on earlier version lens such compactness and more importantly, it presented an improved optical performance than ealier version.

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This compact Nikkor ultrawide has added one extra lens elements in the new optical design with its 11 elements in 8 groups and weighs merely 235g. It retains a similar attachment size of 52mm and eliminates the needs to keep different set of filters with varying diameters. This 20mm Nikkor lens was a popular lens and has rave reviews for its top rated optical quality where it offers high contrast and sharpness across its entire aperture settings. The lens also being designed to have a quick focus operation via its short 72° rotation of the focusing ring from infinity down to 0.3m (1 ft.).

Credit: Image courtesy of "Michelle" " <>. Image Copyright 2002. All rights reserved.

Its highly corrected optical system was specially formulated to tame coma aberration, a common abberation once considered inevitable in wideangle lenses of retrofocus design. Its optical behavor makes this lens particular suited for scenic, architectural, and interior photography. Although this lens has not been equipped with an CRC system for optimizing its close focusing performance, but this 20mm lens can also a superb lens for closeups. When used it in conjunction with bellows and BR-2/3 reverse adpter ring, it is possible to reach an astonishing magnification up to 12X with this tiny sized Nikkor ultrawide. This 20mm lens may be is your good introduction to ultra-wideangle photography because as there are faster optic available now, this little wide vision marvel may be sold very much cheaper than its faster counterpart - the Nikkor 20mm f/2.8s. Although, personally, if you have a little extra budget to spare, always put a priority on a Nikkor 20mm f/2.8 lens which presents a better overall value and performance.

Comparing non-Ai and Ai version of Nikkor 20mm f/4 ultrawide

A rare image of both Ai and Non-Ai version of the Nikkor 20mm f/4.0 Ultrawide Credit: Images of this Non-Ai Fisheye-Nikkor 20mm F4 coutesy of: Russell Gough® <>" All images appeared herein are Copyright © 2003. All rights reserved. Please respect the visual property of the contributing photographer.

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Compare the f/3.5 version with the earlier Ai Nikkor 20mm f/4.0

: Image courtesy of Laura Kornylak ® <> from shutterblade*com where the Company has a website on its own. Image copyright © 2003. All rights reserved. Please respect the visual property of the contributing photographer.

This f/3.5 lens did has an equivalent Ai-S version which was believed to have been introduced around December, 1981. Te upgrade was essential as during that time, a few Nikon SLRs (such as Nikon FA, Nikon FG, F301etc.) were beginning to emerged and they have shutter priority AE and Programmed Auto which might need the Ai Nikkor to update with Ai-S in order they can be more effective in operations.
Technical Highlights: *Ultra-wide 94° picture coverage. * Exceptional depth of field makes this lens suitable for capturing fast-moving subjects or for shooting quickly without focusing. Highly corrected optical system virtually eliminates coma, a lens aberration once considered inevitable in ultra-wideangle and wideangle lenses.

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* Excellent choice for macrophotography; by mounting the lens in reverse on a bellows unit, up to 12X magnification is possible - the highest in the Nikon System of photography. * A light 235 grams - great for travel photography. * Quick focusing through a short 72° rotation of the focusing ring from infinity down to 0.3m (1 ft.). * Takes popular 52mm filters.

Specifications of 20mm f/3.5

Focal length/Aperture: 20mm f/3.5
Lens construction: 11 elements in 8 groups
Picture angle: 94°; Diaphragm: Automatic
Aperture scale
: f/3.5 ~ f/22 on both standard and aperture-direct-readout scales

Exposure measurement: Via Full aperture method; meter coupling ridge provided for AI cameras and meter coupling shoe for non-AI cameras
Distance scale
: Graduated in meters and feet from 0.3m (1ft.) to infinity (
OO); Weight: 235 g
: 83mm dia. x 50mm long (overall): 40.5mm extension from lens flange
Filters:52mm front screw-in; Lens Cap: Front lens cap Snap-on
Hoods: Lens hood HK-6 slip-on type; Case: CL-30S hard leatherette, No. 61; soft pouch, or CP-8 plastic
Usable teleconverter(s):
TC-200, TC-201, TC-14A

NOTE: Serial Number was believed to have been started with 176121 for this Ai version and 210001 for the subsequent Ai-S version.

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Tele-Converters: TC-1 | TC-2 | TC-200 | TC-201 | TC-300 | TC-301 | TC-14 | TC-14A | TC-14B | TC-14C | TC-14E | TC-16 | TC-16A | TC-20E

Recommended links to understand more technical details related to the Nikkor F-mount and production Serial Number: by: my friend, Rick Oleson by: Hansen, Lars Holst

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Credit: MCLau®, who has helped to rewrite some of the content appeared this site. Chuck Hester® who has been helping me all along with the development of all these Nikon websites; Lars Holst Hansen, 'Hawkeye' who shares the same passion I have; Ms Rissa, Sales manager from Nikon Corporation Malaysia for granting permission to use some of the official content; Ted Wengelaar, Holland who has helped to provide many useful input relating to older Nikkor lenses; Some of the references on production serial numbers used in this site were extracted from Roland Vink's website; Hiura Shinsaku from Nikomat Club Japan. Lastly, to all the good people who has contributed their own expeience, resources or kind enough granted permission to use their images of their respective optic in this site. It is also a site to remember a long lost friend on the Net. Note:certain content and images appeared in this site were either scanned from official marketing leaflets & brochures published by Nikon and/or contribution from surfers who claimed originality of their work for educational purposes. The creator of the site will not be responsible for may discrepancies arise from such dispute except rectifying them after verification. "Nikon", "Nikkormat", "Nippon Kokagu KK" & "Nikkor" are registered tradename of Nikon Corporation Inc., Japan. Site made with an Apple IMac.