Pentax DFA 100mm f2.8 WR macro

After Pentax switched to digital in 2004, it began releasing a series of “DA limited” lenses. The DA prefix applies to a series lens Pentax produced exclusively for their APS-C digital DSLRs. The “limited” tag is more of a marketing slogan. These are not limited edition lenses. The tag really goes back to three lenses Pentax had released in their previous FA series, the FA 31 limited, the FA 43 limited, and the FA 77 limited. These lens quickly assumed a place among Pentax’s very best lenses, and avid connoisseurs of SLR optics raved about them, even going so far as to declare them the three best autofocus lenses ever made. Although they are very good, the DA limited lenses are not quite on the level of the three FA limiteds. The limited tag was used to draw attention to their finer qualities — to declare, as it were, that these lenses are in a very special, limited class. What the DA limiteds offered was superb build quality, excellent optics, and remarkably compact size. Three of the limiteds are pancake lenses, one of which protrudes from the camera about half an inch. The lenses are made almost entirely of metal and glass. They are exquisite little jewels. Neither Nikon or Canon or Sony have anything quite like them in their lineups.

What does all this have to do with DFA 100 f2.8 macro lens? Well, simply this: while the DFA 100 is not a limited lens, it very well could be, with its solid aluminum housing and compact design, its dampened focus, and its superb optics. Ned Bunnell, president of Pentax Imaging in the U.S., has admitted its similarities with the limited line of lenses. In any case, it is the only non-limited Pentax lens that shares a strong kinship with the DA limiteds. It could easily have been called a limited. Why, then, wasn’t it?

For two reasons. First, unlike the limiteds, the DFA 100 features WR seals that protect it against moisture. While it’s not submergible, it should be fine in a mist or a rain shower. This makes it possible to pursue macro photography in the rain (provided one uses the lens with a Pentax WR body like the K-5). Secondly, the DFA 100 is considered to be both a digital and a film lens: that’s what the DFA moniker (as opposed to merely DA) stands for. It’s not clear why Pentax wishes to advertise the film capabilities of the lens. After all, Pentax no longer makes film cameras. Nor can it be due to the width of the lens’s image circle. Not all the DA lenses are fit only for use on APS-C DSLRs. Several lenses, including the DA 40, the DA* 55, and the DA* 300 are (supposedly) fit to use with either 35mm film or with full-frame sensors.

What of the lens itself? How does it perform? What are its strengths and weaknesses?

Wide open, the lens works well as a portrait lens, with commendable sharpness and excellent separation. Bokeh is superb — to be sure, not as good K50/1.2 (but then what lens is?), but better than, say, the Pentax 50/1.7 or 50/2 lenses. The lens produces bright, vibrant, stunning color, much like the DA* and limited lenses. Below are some kitty portraits taken at f2.8:

A macro lens is specially designed with close-up photography in mind. The Pentax DFA 100 f2.8 macro does not disappoint in this respect. With its circular aperture blades, it retains excellent bokeh even when stopped down, as in the following pics taken at f16:

As one focuses closer, the DOF gets narrower and narrower. Sometimes this requires stopping down to retain a tolerable degree of focus. But sometimes one wants the razor thin DOF to create stunning artistic effects. The DFA 100 doesn’t disappoint in this regard either, as the following photos, all taken wide open, demonstrate:

As the lens is f2.8 wide open, it cannot expect to achieve as creamy a bokeh as an ultra fast lens like the K 50/1.2. So Pentax appears to have decided to add some special rendering to the bokeh to give a more artistic effect. Instead of seeking merely the generic, smooth buttery effect of faster lenses, the DFA 100 sometimes features (depending on the background) a more artistic, pastel-like bokeh, somewhat along the lines of the FA 77 limited and DA* 55:

What is perhaps most appealing about the DFA 100 f2.8 macro is that it crams its spectacular optical performance in so small a package. The lens weighs only a little more than 12 ounces. It takes 49mm filters and is little over 3 inches in length. In comparison, the MicroNikkor 105 f2.8 VR weighs almost 28 ounces, uses 62mm filters, and is an inch and half longer. The Canon 100 f2.8 IS macro weighs 22 ounces, is over 5 inches in length, and uses 67mm filters. Both the Canon and Nikon macros are internal focusing. That is regarded as a feature, but it could just as easily be regarded as a defect, as internal focus lenses achieve close focus at the expense of focal length. At 1:1 magnification, the Canon macro is merely a 78mm lens; the MicroNikkor 105 a 94mm lens. No such internal focusing “feature” plagues the Pentax DFA 100. It’s an external focusing lens through and through, which allows it to retain its 100mm focal length all the way to 1:1 magnification, making it more useful as a tool for photographing mini-critters: