The “flat front” look

If you look up the term “flat front” these days, you’ll likely be directed to a selection of pants.
But there was a time when a series of lenses were sought out by photo buffs that had flat fronts of their own.
Well… technically, the correct description is “plano-concave”. But with one look at one of these older zoom lenses, you can’t help but notice that the front element shows a perfectly flat surface to the outside world. The inside surface of that element is strongly convex (meaning you could use it as a water dish, if you could get at it).
The earliest one of this type I can remember (and there may be earlier ones I have never seen) is the Vivitar Series 1 28-90mm from around 1981 or so. I can’t find an exact introduction date, but I do remember it made a bit of a splash at that time because it was one of the first zoom lenses to break the 35mm barrier. There had been lots of short-range zooms that went from 35mm to 70mm, even 85mm – but most photographers by the late ‘70s considered a 28mm wide angle a must-have. So, a zoom lens that started there, and got you right up into short telephoto portrait range was a big deal.
Of course, this new Vivitar wasn’t technically a zoom. It is “varifocal”. If you zoom from one end of the range to the other, it only stays in focus at infinity. All other focus distances require you to refocus when you zoom. This was a bit inconvenient, but it did allow the lens to get down to less than 25cm at 28mm (less than 1m at 90mm). This was pretty cool. Over a decade later you may remember the early Tamron 28-200mm with a close focus of 2 meters at all lengths – not so great for wide angle closeups – crappy actually.
I’m sure that weird flat front element had something to do with the Vivitar’s performance, especially since people who had it praised its sharpness. I can only think of a few other manufacturers making similar-looking lenses at that time. I know Pentax did, as did Zeiss-Contax.
Why the design never flourished much beyond the early ‘80s is probably due to autofocus. It doesn’t take much fiddling with the Vivitar to realize that front element is heavy and does all the work in focusing. Adapting it to the lightweight needs of AF mechanisms and motors likely wasn’t all that practical, and optical designers had to look elsewhere for their upcoming wide-to-tele zoom designs. Today, the only place I see the flat “plano-concave” front elements used is in wide angle or fisheye converters sold for video-camera use, (or sold to on-line suckers who think they’ll adapt to their SLR lenses without hideous softness and blurring).
But the question remains, was the flat-front variofocal lens really any good, if they disappeared so quickly?
Well, the nice thing today about larger sensor DSLRs is you can put older optics to the test, right to the edges of their frame – so I dug out a Vivitar Series 1 28-90mm f2.8-3.5 (yup, a nice fast aperture) in a Nikon mount. It hadn’t been used in awhile, so I found I had to service the sticky aperture blades -but once done, it was time to test, test, test.
I put it up against a series of prime Nikkors, which is hardly fair to an elderly “varifocal” zoom – but at least it was a benchmark with which I was familiar.
My conclusions are thus – at all settings, the Vivitar was beaten by the Nikkor primes – but mainly because the Vivitar’s edges were noticeably soft, and prone to chromatic abberation when wide open, along with overall flare across the image – nothing uncommon there. But if we were to consider that the most important subject matter of our photos is likely in the central 2/3 to 3/4 of the image area, the Vivitar delivered the goods. It was decently sharp, especially when used around f5.6 or f8. And those fuzzy edges, and some corner vignetting that was present throughout the range, would have realistically disappeared when cropped away by the minilab, or been hidden under the edges of the slide mount of the day. You can certainly understand why customers were pleased with this stocky, chunky optic. As as walk-around lens when on the family vacation, it worked exactly as intended. I have seen much worse performance, at much higher price points than even this expensive-for-its-time Vivitar.
It’s only in this digital age, when we peep at the corner pixels at 100% on our screens that we fret about every little flaw (although there are quite a few mediocre optics out there that seem to get away scot-free by a large number of DSLR users – probably because they actually look at their images as photographs, and not just clusters of pixels on their screens).
My sample of the Series 1 has a slightly warm colour balance, which is easily fixed these days when editing- not so easy when people shot slides.
I would also evaluate its “bokeh”, or out-of-focus quality as being much better than many zooms I’ve tried. In fact, it was better than the 50mm 1.4 Nikkor at f8.0. If you’ve ever had a zoom give you a decent in-focus image, but a harsh, jaggedy out-of-focus background, you’ll know what I mean.
It’s no secret that many photographers new to the game are buying up older manual lenses in search of image qualities (and smooth focusing) that are alternatives to the current crop of plastic body zooms. The question is whether there is a home for these older, slightly unconventional zooms (or varifocals) now that sensor sizes allow them to be used as intended.
I may have to take this Vivitar out for the day when the weather warms up, and see if I can learn to appreciate it more fully.

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~ by windsorphotooutfitters on January 25, 2013.

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