Still-photography camera lens
The W Rokkor 21mm lenses are a series of three prime wide angle lenses produced by Minolta for Minolta SR-mount single lens reflex cameras. The first 21mm lens released was the W Rokkor-PI 21mm f/4.5 (1962), which featured a symmetrical design similar to the contemporary Zeiss "Biogon". This was succeeded by the W Rokkor-QH 21mm f/4 (1963), with slightly improved speed and similar symmetric construction. The third and final 21mm lens was the MC W Rokkor-NL 21mm f/2.8 (1971), which featured a retrofocus design that did not require the reflex mirror to be locked up, allowing use of the built-in viewfinder.
Design and history.
Minolta updated the design several times during the course of production; the first two versions were symmetric designs which required the reflex mirror to be locked up, while the third version was a retrofocus design, followed by a cosmetic update in 1973.
When the Rokkor-PI ;templatestyles src="F//styles.css" / ;f/4.5 was introduced, it was advertised as "a product of much painstaking work and research by the company's technical staff", which Erhard Bertele called "a mockery" in retrospect, declaring it "[an imitation of the "Biogon"] with seemingly insignificant small changes to the original Bertele design". The similarities in lens design between the "Biogon" and the Rokkor-PI ;templatestyles src="F//styles.css" / ;f/4.5 have led to speculation the latter was discontinued in favor of the Rokkor-QH ;templatestyles src="F//styles.css" / ;f/4 in response, as the -QH shares a similar 8-element, 4-group design as the Nikkor-O 2.1cm f/4 (1959). In 1964, the suggested retail price of the Rokkor-PI ;templatestyles src="F//styles.css" / ;f/4.5, with accessory viewfinder and leather case, was US$. By 1968, the successor Rokkor-QH ;templatestyles src="F//styles.css" / ;f/4 retailed at a lower price, US$, with a dealer cost of US$.
The Rokkor-NL ;templatestyles src="F//styles.css" / ;f/2.8, introduced in 1971, has three floating elements to compensate for focusing aberrations at close range. It was replaced by the MD Rokkor 20mm ;templatestyles src="F//styles.css" / ;f/2.8 lens (1977), which was more compact and lighter.
References.
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