Pentax F 70-210 f4-5.6

The SMC Pentax F 70-210 f4-5.6 was Pentax’s very first auto-focus telephoto zoom lens. It was released in 1987. It replaced the well-regarded A 70-210 f4 lens. It’s not clear why Pentax choose to dispense with the constant aperture in the AF telephoto zoom lens. Probably to cut down on the weight. The A version weighs 680 grams; the F version, 555 grams. Not a huge savings in weight, but perhaps critical for the AF function. In any case, the F 70-210 would remain one of the heaviest non-star AF zoom lens Pentax has ever released. The only non-star AF lens heavier are the early AF 35-70 f2.8 and the F and FA 100-300 f4.5-5.6.

What accounts for the weight? The lens features 13 elements in 9 groups. The FAJ 75-300 f4.5-5.8 features 12 elements in 9 groups and weighs only 385 grams. The weight difference doesn’t appear to be exclusively due to the weight. There is a bit more metal in this lens then in many of Pentax’s other auto-focus lenses. The aperture ring, zoom ring and narrow focus ring are all plastic, as, I believe, is the filter thread. And there are a few other parts that are plastic as well; but much of the lens is metal. This is not a cheap budget or even consumer grade zoom lens. This is closer to being a mid-range zoom lens. Pentax would not introduce a comparable variable aperture telephoto zoom until the DA 55-300 f4.5-5.8.

As typical for non-professional telephoto zoom glass, the F 70-210 is sharpest at the wide end of the lens and slowly loses resolution toward the long end. While there’s little difference between, say 70mm and 90mm, by 120mm the resolution loss is detectable, and it becomes more and more obvious as one zooms toward 210mm. The lens maintains excellent contrast and superb color rendition throughout the zoom’s range, with a slight loss of contrast on the long end. This is not a lens that will necessarily deliver “accurate” color, but it does produce rich, vibrant, distinctive hues, that works very well in landscape photography.

One word of warning, however. This is an older lens with quite a bit of glass in it, and it’s more than a tad susceptible to veiling flare, with loss of contrast/microcontrast, especially when shot on bright, sunny days. Behavior here is sporadic and difficult to predict. But if you note a loss of contrast, that is probably what is happening. Under good lighting conditions, this is a fairly contrasty lens, as the following images demonstrate:

Resolution at 70mm, though not outstanding, is nonetheless very good, particularly when stopped down to f8 or so, as we see in the following image, accompanied by a 100% crop:

Comparable resolution can be found at 95mm:

By 135mm, we’ve lost a little resolution, but it’s still pretty good:

At 210mm, resolution drops to merely good, with a hint of softness beginning to cause issues with the 100% crop:

The 210mm shots were taken at f6.3. Stopping down a bit does give a slight boost in resolution, and the F 70-210 provides its best results between f6.3 and f11. Wide open performance is respectable, and the bokeh is actually very good for a slow, variable aperture telephoto zoom lens, as we see in this wide open shot (i.e., f4.5) at 125mm:

The results are even better if you can get up close, as in this shot, at 110mm, f4:

Or this shot taken at 210mm at f5.6:

Or this shot taken at ~f4.5 at 155mm:

The F 70-210 auto-focuses fairly well: quick and accurate. It will not please the silent focus snobs; but then again, if the lens had been built with a silent focus motor, it would not likely still be working as an auto-focus lens some 25 years after it’s introduction. This is a lens built, perhaps not for the ages, but at least for the decades. It’s perhaps best used nowadays as a kind of compact, budget telephoto landscape lens (although watch for veiling flare on bright days!). But in a pinch it can be used wide open for the more traditional isolation effects that longer lens are often best suited for. It won’t quite match what can be extracted from an f2.8 telephoto zoom. But a 70-200 f2.8 lens would cost a great deal more, and weigh near three times as much into the bargain. On the used market, the F 70-210 usually runs somewhere between $100 and $150. For that price, you’ll be hard pressed to find a better Pentax K-Mount telephoto lens.

More examples:

@ 70mm, f8:

@ 70mm, f10:

@ 78mm, f5.6:

@ 145mm, f8:

@ 210mm, f5.6