Hello, my name is Yasuhiro Ohsone. I have been involved in SIGMA’s product development for more than 30 years. In this column, I talk about how past products were created and the peculiarities that make them stand out; provide some background information on how the camera and lens market has developed; and share anecdotes about mistakes and failures – only the ones I’m not too embarrassed about, though.
In this third entry in the column, I would like to talk about the history of SIGMA’s 28mm prime lenses.

SIGMA’s history of 28mm prime lenses

On January 25th 2019, SIGMA’s new 28mm F1.4 DG HSM | Art lens became officially available for purchase. 28mm has been the most popular wide-angle focal length since film camera days and enjoys great popularity even today. As a way of celebrating our latest release of a wide-angle lens with such a classic focal length, I want to take a look back at SIGMA’s own history of 28mm prime lenses.

SIGMA’s very first 28mm lens was the 28mm F2.8 WIDEMAX. It was released around the year 1970 (I can’t provide a more detailed date for lack of reliable sources).
A 28mm focal length with an aperture of F2.8 seems rather ordinary today. Back then, though, an F-stop of 2.8 was exceptionally fast.

The 28mm WIDEMAX featured a so-called retrofocus lens design. Most wide-angle retrofocus lenses at the time were built with the following lens setup: a large, convex front element, then a powerful concave lens. These two lenses act as a “wide converter”. The part is then followed by four single lenses (convex-concave-convex-convex) that act as a “main lens”. If you look at Figure 1, you’ll find the WIDEMAX also followed this design. Similar to Nikkor’s 28mm F3.5 or the Super Takumar 28mm F3.5, the front lens element was quite large – and yet, while this design ensures great optical quality, it is very difficult to build it with large apertures. Accordingly, many 28mm lenses had an F-stop of 3.5 or higher.

F2.8 – the stop that made a difference

Compared to other lens manufacturers, SIGMA entered the market relatively late. A fast F-stop of 2.8 was an ideal way to set SIGMA apart from competitors and make our products stand out from the rest.

With single-lens reflex cameras, the brightness of the image in the viewfinder depends entirely on the brightness of the lens attached to the camera. A bright aperture of F2.8 meant a great difference for the photographer. By using two glued-together lenses instead of a single lens for the final element, SIGMA managed to achieve an F2.8 aperture without a significant size increase compared to F3.5 models.

The brightness afforded by the lower F-stop made the SIGMA 28mm F2.8 WIDEMAX an incredible popular item. Then-president Michihiro Yamaki’s conclusion: “F2.8 sells.” All of SIGMA’s fixed focal lenses – the 24mm, 35mm, 135mm and lastly the 200mm lens – were designed to allow an F2.8 aperture. Together with their unique optical characteristics and ease-of-use, they proved very appealing lenses.

After the introduction of lens multi-coating in 1973, the lens design also found use in SIGMA’s 28mm F2.8 WIDE in 1974, the SIGMA Z 28mm F2.8 in 1975, and even the SIGMA XQ 28mm F2.8 in 1976.

A 28mm wide-angle lens like no other

The retrofocus lens design was still making progress, of course, and in 1978, SIGMA launched two different 28mm wide-angle lenses almost at the same time. One of them, the SIGMA MINIWIDE 28mm F2.8, applied the retrofocus principle to the entirety of the lens, thereby achieving a more compact lens design – and a minimal focusing distance of only 0.22m.
The other lens, the SIGMA FILTERMATIC 28mm F2.8, employed a longer lens barrel with four internal color filters that are switchable.

Thanks to its macro abilities and its low price, the MINIWIDE became one of SIGMA’s best-selling products for the following eight years. In 1985, SIGMA released a successor model (the MINIWIDE II), featuring a redesign with one less glass element; it remained in production until 1995.

The FILTERMATIC, with its internal color filter technology, managed to attract a lot of attention. This attention, however, didn’t translate into sales, and the lens disappeared from the market only two years later. I actually own a SIGMA FILTERMATIC 28mm F2.8, and seeing the filters fluttering and switching within the lens barrel is an interesting experience. These color filters – cyan, yellow, orange and skylight (almost see-through) – were a great fit for the monochrome film era, but they failed to be of use for color photography.
(In black-and-white photography, yellow and orange color filters are used to enhance the contrast of the image.)

The 28mm released during the primes’ dark age

In the course of the 1980s, the 28mm wide-angle lens suffered a sharp drop in popularity. The reason lies in the evolution of the zoom lens in the 1980s, zoom lenses starting at 28mm started selling from many manufactures in large numbers, which cut into the sales of 28mm prime lenses.

And yet, in 1985, SIGMA released a new prime lens. It was a lens that made a unique promise: “zero vignetting.” The lens went on sale as the SIGMA NON VIGNETTING 28mm F2.8. However, the term “vignetting” was not yet in widespread use, and so later versions instead used the name SIGMA H,L (Highlight) WIDE 28mm F2.8.

Diminishing brightness towards the edges of the image is an inevitable problem with wide-angle focal lengths such as 28mm, due to the so-called “cosine fourth” law. Additional loss of peripheral brightness due to the large aperture (vignetting) only strengthens the effect. While there is no escaping the merciless “cosine fourth” law, SIGMA managed to erase vignetting through an optimal mutual configuration of each lens group within the retrofocus design. This method also minimized “coma aberration,” a color fringing effect that occurs as the amount of light increases. SIGMA had created a wide-angle lens with very little vignetting and – an additional plus – without the unsightly swirly bokeh pattern caused by vignetting of out-of-focus areas.

The lens was the culmination of SIGMA’s research and experience with 28mm F2.8 lenses. Although its price was on the expensive side, the lens became an extremely popular item with lens maniacs and photography enthusiasts. Even so, the lens could not compete with the irresistible allure of zoom lenses and went out of production after a few years.

In 1985, the release of the MINOLTA α7000 announced the new age of autofocus SLRs. The autofocus feature invigorated interest in the SLR market, and as zoom lenses improved even more in features and optical quality (aspherical elements, special low-dispersion glass etc.), they pushed fixed focal length lenses – from 28mm to 35mm, 100mm, 135mm up to 200mm – into oblivion. The “dark age of the primes” had begun.

In the next column, I will explain in detail about how the 28mm lens managed to make its come-back from this dark age.