Pentax FA 20-35 f4

The Pentax FA 20-35 f4 was released in 1998. It replaced the much older F 24-50 f4, whose lineage can be traced all the way back to the A 24-50, an old manual focus lens from the mid-eighties. In other words, the FA 20-35 was a long over-due lens, Pentax’s first purely wide angle zoom. The lens was designed (or at least patented) by Takayuki Sensui, who would, a few years later, join Nikon and work on the development teams for the Nikkor 17-55, the Nikkor 105 Macro, and the Nikkor 24mm TSE lens, among other designs. The late nineties were a sort of an Indian Summer for Pentax. The company had hemorrhaged users to Canon and Minolta in the mid-eighties as a result of tauto-focus technology in lenses, in which Pentax was slow to adopt; and later would hemorrhage more users to Nikon and Canon as a result of being late to the digital party. But in the late nineties, as the company struggled to keep up with Canon, Nikon, and Minolta, they suddenly started churning several lenses that would quickly gain the reputation for enjoying legendary status: the three FA limiteds and the FA* 200 f4 macro. This period also saw the introduction of the under-rated FA 35 f2 and Pentax’s best full frame variable aperture zoom, the FA 24-90 f3.5-4.5. What these lenses all share, whether they are legendary limiteds or a mid-level zooms like the FA 24-90, is Pentax’s new “ghostless” coating, which improved flare control, lens contrast, and color rendition. These “ghostless” lenses share the cooler FA color rendering, with it’s rich blues and greens, except the colors now seem even more vibrant and distinct. While the FA limiteds and the 200mm macro are the star lenses of this period, both in designation (in the case of the macro) and in performance, the FA 20-35 is the best of the zoom lenses. Compact, short of range, yet optically very strong, with excellent edge to edge sharpness and superb contrast. While not in the same league as the limiteds, the FA 20-35 is arguably the best of Pentax’s non-star zooms designed for film cameras, and a precursor for the recently released DA 20-40 limited. And yes, it really is that good.

I’ve only shot the lens on an APS-C DSLR, so I cannot say how it performs with 35mm film, or how it might perform on an FF digital camera. On APS-C it makes a terrific standard zoom lens for landscape photography. What it loses in range on both ends it makes up for in optical quality and compact size. Let’s take a look at some crops to see how well the lens resolves detail.

First, the complete picture, taken at 20mm and f8 on the Pentax K-5. Note the excellent color rendition of the image and the contrast:

Now the center crop:

And the corner crop:

What I see here is strong center performance and slightly less strong corner performance. Let’s try another 20mm image, also shot at f8:

First, the complete image:

Now the centerish crop:

And the corner crop:

Again, we find very good center and corner performance. Corners seem perhaps a tad better in this set of samples than the previous, which may be a consequence of some mild field curvature in the lens. However, the difference is so slight as to be utterly without significance.

Let’s move on to 28mm. Again shot at f8:

The center crop:

The corner crop:

This time, the corner doesn’t seem quite as sharp as the 20mm corners, while the center, if anything, might be a tad sharper. Nonetheless all around very good performance.

Let’s attempt a 29mm shot, with the focus point at some distance. Again, we’re shooting at f8. We begin with the full image:

Now the center crop:

And the edge crop:

It’s difficult for any lens to resolve such fine detail at a distance. Even so, what I see here is only a mild reduction of resolution near the edge. Not bad, but a palpable diminishment nonetheless. There could be field curvature causing this, or reduced resolving power, or some combination of these two factors. But I think it’s safe to conclude on APS-C, the FA 20-35 may be a little less sharp toward the edges at 28mm than at 20mm.

Now to the long end of the lens, 35mm! Once again, we shoot at f8 and begin with a full sized sample:

The 100% center crop:

And the 100% edge crop:

Similar to what we’ve seen at 29mm. How about another example at 35mm, f8? Here’s the complete shot:

The 100% center crop:

And the 100% corner crop:

The pattern emerging from all these shots is that, because of it’s short range, there’s a great deal of consistency between the wide end and long end of the FA 20-35. No major weak points. Maybe it’s little sharper on the wide end, especially toward the edges, but you really have to pixel peep to notice, and in terms of practical output, it just doesn’t rise to the level of significance.

Just for fun, let’s take a look at the performance of the lens close to wide open, af f4.5, 23mm:

And the 100% center crop:

And the 100% corner crop:

As can be seen, even close to wide open, the performance of the lens is really quite good, with maybe a little less resolution in the corner crop, but otherwise it’s difficult to ascertain the difference in performance between the f4.5 shots and the f8 shots.

But more important than the resolution is lens contrast and color rendition, and in those two categories, the FA 20-35 really excels, especially for a non-star, non-professional f4 zoom. Consider the following comparison with the DA 15 limited (the first shot is with the DA 15, the second with the FA 20-35):

The FA 20-35 seems a bit warmer than the DA 15, but in nonetheless comes close to holding it’s own. The DA 15 renders better and has a bit more lens contrast. It will consistently deliver better results than the zoom; but the zoom’s not far behind. Indeed, the FA 20-35 comes closer to achieving prime-like performance than any other zoom I’ve ever used, and I’ve shot with nearly all the best slow standard zooms produced by Pentax for the K-mount.

Build quality for the FA 20-35 is good but not outstanding. Although the mount is metal, most of the rest of the lens seems to be made out of plastic. Even so, the lens feels well made. Since the lens barely extends when zooming and features internal focusing, there’s no wobbly barrel to contend with. The focus ring, as is common with internal focus AF lens, is pretty loose, with no dampening at all. The mostly plastic construction keeps the lens on the light side: it weighs 245 grams (just over half a pound). I’m not aware of a lighter FF zoom lens with comparable quality.

In Photozone’s review of the lens, they wrote:

The Pentax SMC-FA 20-35mm f/4 AL is a very good lens but it doesn't really offer much over its successor — the SMC DA 16-45mm f/4 ED AL. Similar to its cousin it has one primary problem: lateral CAs (color shadows at harsh contrast transitions) at 20mm. Other than that the lens is capable to produce a very good resolution and comparatively low distortions and vignetting.... The lens had its days during the film era but it's time to move on now.

Let me address the CA issue. Online reviewers make a big deal about CAs, even though in digital photography, most CAs clean very easily in a raw converter like Lightroom. Why are reviewers still so uptight about so minor an issue? Because CAs can be measured. That is the only reason. If they couldn’t be measured, we would hear a lot less about them. Here’s the truth about CAs. Most zoom lenses are prone to them. Some zoom lenses are a little better than others. But the fact that one zoom lens produces CAs 2 pixels wide and another produces CA 2.5 pixels wide is insignificant. What is significant is whether the CAs will clean up in Lightroom or another raw converter (or in camera, if the photographer is shooting jpegs). If they are easy to get rid off via software, they’re not an issue. If you don’t want to fix the CAs in post, shoot Zeiss and Leica primes. Otherwise, use software to fix the CAs and stop making a big deal about them. In the age of digital photography, CAs are rarely of any significance.

Perhaps more revealing in the Photozone quote is the assertion that the FA 20-35 doesn’t really offer much over its successor, the DA 16-45. I’ve shot with both lenses and can say without any reservation that this simply isn’t true. The FA 20-35 is small, lighter, more compact than the 16-45. It doesn’t have an extending barrel that wobbles. And it’s a better lens at all focal lengths. It has a bit more lens contrast and better color rendition. It produces images that are more pleasing, aesthetically, to human perception. The differences may be subtle, but they are palpable to a discerning eye. With the FA 20-35, you give up a bit of range at both ends, but in return you get a smaller lens with no extending barrel that produces better images. Photozone’s claim that the FA 20-35 “had its days during the film era but it's time to move on now” is little more than gearheadism and measurebation gone amuck. It’s statements like that which reveal the poverty of review sites that attempt to determine the quality of the lens via measurements. Photography, last I checked, is an aesthetic pursuit; and how lenses perform in the field must be judge qualitatively, in relation to human perception and human aesthetic values, not from “objective” measurements interpreted by gearheads.

More images taken with the FA 20-35. These have all been PP’d in Lightroom. Even so, changes to contrast and color have been minor. And remember the adage of photographers (as opposed to mere gearheads): Look, don’t measure!

The following images were taken at 20mm:

At 23mm:

At 24mm:

At 26mm:

At 28mm:

At 29mm:

At 32mm:

And finally, at 35mm: