Introduction to the Petzval lens
By Andy Westlake
|The Lomography Petzval 85mm F2.2 is a recreation of a 19th century lens, complete with brass barrel|
Lomography isn't a company we've historically talked about much on DPReview; with its emphasis on low-fi, 'shoot from the hip' photography using plastic film cameras, it's a long way from the typical interests of our readers. But last year the company came up with an interesting idea: to recreate a classic 19th century portrait lens for modern SLRs. After a wildly successful Kickstarter campaign that raised well over $1m, the result is the Petzval 85mm F2.2, which is available now to fit Canon or Nikon SLRs.
You can read all about it on Lomography's own site, but in essence the company has tried to make a faithful reproduction of a lens designed in 1840 by Joseph Petzval - one of the foremost optical physicists of his day. Previous photographic lenses tended to have very small maximum apertures, and this resulted in extremely long exposure times (especially with the low sensitivity of early photographic processes). Petzval overcame this by designing a lens which used four elements in two couplets, and could be made with the then-impressive maximum aperture of f/3.7, allowing exposure times measured in seconds rather than minutes.
Peripheral aberrations limited the angle of view to about 30°, which corresponds to about 80mm on full frame. But in combination with fast aperture, this made Petzval's design ideal for taking portraits, which quickly became a staple of the photographic studio. It took many years before the optical design was significantly improved.
Since then, of course, lens design has come on in leaps and bounds, and modern portrait lenses like the Sony Carl Zeiss Planar 85mm F1.4 or Canon EF 85mm F1.2L II USM are on an entirely different level technically. Computer-aided calculations mean that these multi-element designs combine large apertures with remarkably low levels of optical aberrations. So why on earth would you want to revisit a design that's over 170 years old? The answer lies in the aesthetics of the images it produces.
Aberrations for art's sake
|'Swirly bokeh': this image illustrates the Petzval's characteristic look|
It's the very imperfections of Petzval's design that have inspired the lens's resurrection. These flaws, including field curvature and vignetting, give a characteristic look to the images it creates that some photographers value highly, and which really can't be mimicked in post-processing. In the DPReview office we'd call it a 'stunt' lens: one which you'd use for very specific purposes and effects. It's most certainly not for every image, or indeed for every photographer; in fact we're pretty sure that the majority simply won't see the point. But some will exploit its characteristics to produce compelling images that really couldn't be achieved any other way.
No matter what you think of the images it produces, it's difficult to deny that the Petzval is a beautifully-crafted object. Lomography has been determined to reproduce the design right down to its engraved brass barrel, rack-and-pinion focusing, and drop-in apertures. The result is unlike anything else you can buy.
|The lens's elaborately engraved brass barrel, focusing knob and drop-in apertures are designed to give an authentic recreation of Joseph Petzval's 1840 design. Only now with a choice of Canon EF or Nikon F mount.|
First there's that attention-grabbing barrel. Put this lens on your camera and walk around with it for an afternoon, and complete strangers will stop you to ask about it. In London. If you want to use it for discreet street portraits, be sure to order the black version.
The brass barrel may be mainly a cosmetic affectation, but the the mechanics of the lens are a different matter. The lens uses rack-and-pinion focusing: a prominent knob on the lower left side moves the optical unit back and forwards in the barrel. In practice this works surprisingly well, but don't expect to hit pin-sharp focus shot-after-shot. The viewfinders of modern SLRs aren't really optimised for manual focus, and don't have such aids as split-prisms and microprisms, which means focusing can be a bit hit-and-miss. Then again if you're after pin-sharp images, this probably isn't the lens for you anyway.
The drop-in Waterhouse stops are wonderfully retro, and a constant reminder of why the aperture diaphragm was invented. They're just hugely impractical - to change the aperture you have to root around in your pocket or bag to find the correct stop, by which time your subject may well have acquired a more bored expression than you were aiming to capture. Overall it's easier to just pick one and stick with it - there's not much point in buying this lens and shooting it at F11, anyway.
Sightly disappointingly, our Canon-mount loan sample didn't actually sit tight on the camera, but wobbled around a bit. We don't know if this is typical of all copies of the lens, but we'd certainly expect better if we'd spent our own money on it. And while that brass barrel and retro design is lovely, we can't help but comment on the stylistic mismatch it offers against a modern AF SLR. It might work on an old manual focus film SLR, or possibly the Nikon Df, but with the Canon EOS 6D the lens just looked a little out of place.
Let's get one thing straight to start off with - the Petzval isn't a modern lens, and you shouldn't buy it expecting 'sharp' images. Instead using it is all about exploiting the unusual optical signature that the lens offers.
Wide open, where it looks most interesting, the Petzval has a rather small area of central sharpness, surrounded by ever-increasing blur. Backgrounds are rendered with oval out-of-focus highlights, giving a characteristic 'swirl'. Even the central 'sharp' region isn't really sharp by modern standards, but stopping down progressively improves this, while increasing the central area that's acceptably sharp, and toning down the background blur.
It really is a portrait lens
We sometimes get criticised for calling short telephotos in the classic 85-135mm range 'portrait lenses', as if it implies that they can't be used for anything else (rather than just being a handy shorthand describing what they're especially well-suited for). But the Petzval really is a portrait lens - its optical characteristics are best-suited to drawing attention to a single subject. It could be stopped down to F11 and used for landscapes, if you really wanted to, but even at that aperture the edges of the frame aren't truly sharp. So there doesn't seem to be much point - an 85mm F1.8 prime will be cheaper and sharper.
Assessing the lens is therefore very much down to your own photographic interests and style. Personally, as much as I loved the lens's build quality and the idiosyncratic design, I quickly found out that it doesn't really lend itself to how I like to shoot. I also found its drop-in / drop-out apertures infuriating, and can't help but think that it would be great to see these optics in a modern lens barrel with focus and aperture rings. Admittedly it would reduce the charm, but it would surely be cheaper to make, and more practical to shoot with too.
So, the Petzval doesn't especially suit me, but that's just one point of view. Turn to the next page for a second opinion and wider perspective.