Pentax FA 100-300 f4.7-5.8

The Pentax FA 100-300 f4.7-5.8 has an interesting lineage. Pentax released it’s first 100 to 300mm zoom in 1991, with the FA 100-300 f4.5-5.6 PZ. That lens was replace in 1996 with the F 100-300 f4.5-5.6. This is the only time an FA lens was replaced with an F lens. The only difference between the two lenses is that the F lens lacks the power zoom feature. In 2000, Pentax began to introduce a new batch of FA zooms in a faux silver finish, beginning with the FA 100-300 f4.7-5.8, which replaced the F version. It is often attested that the final and slightly slower 100-300 is the best of the batch. Having never used the other two, I can’t confirm that. Nonetheless, it really doesn’t matter all that much. None of these lens ascend beyond the merely serviceable level. Although the FA 100-300 f4.7-5.8 has developed a bit of a reputation on the web for being a hidden gem, it’s a reputation that is hardly deserved. Although it has its good points, this is hardly a great or even a particularly good lens. What distinguishes it is decent contrast and good color rendition. In terms of resolution it’s about what you would expect in an inexpensive consumer grade zoom: no better or no worse than the rest of them. It is a tad more consistent than many of the cheap telephoto zooms in that there isn’t significant drop in resolution between the short and long ends. It does lose resolution as you head toward 300mm; but not as much as most lenses of its type. However, it really doesn’t have that much resolution to begin with, so this is hardly any great merit!

Let’s glance at what the lens starts out with toward the wide end. Here’s a 100% crop at 145mm:

Hardly spectacular. In fact, it’s downright mediocre. To get a sense of perspective, consider a 100% of the same animal taken with the Pentax DFA 100 macro:

Now that’s a sharp image! So any reports you here of the FA 100-300 enjoying “outstanding sharpness” are patent nonsense.

Another example, this time at 100mm:

Not bad at web resolution. Now let’s glance at the 100% crop:

That’s less inspiring. To gain some perspective, let’s glance at the same subject shot with the Pentax A 35-105 at 105mm (100% crop):

While there’s not a huge difference, the A 35-105 image is clearly sharper, with better overall rendering.

Even more problematic, is very poor border to border performance. Consider the corner on the Square Tower image:

Not at all good, particularly considering this is full-frame lens shot on an APS-C DSLR. If you want your corners to be sharp, this is a lens to be avoided.

At 300mm resolution is adequate for web resolution, but clearly suffers at 100% resolution, as demonstrated in the following two images, the second a 100% crop of the first:

Despite it’s weakness in terms of resolution, colors are quite good. Indeed, not many cheap consumer grade lens render color quite as well the FA 100-300:

The bokeh of the lens is decent as well, as seen in this shot taken at 300mm:

The FA 100-300 f4.7-5.8 is an excellent snapshot lens, capable of striking color and better than average rendering. It is a compact and light-weight lens perfect for taking on hikes and casual trips. However, the lens does not exhibit the sufficient amount of resolution required for more serious work. Resolution is at a premium at longer telephoto focal ranges. If you want to get sharp images from a telephoto lens with a Pentax DSLR, you’ll need a lens like the DA* 60-250 f4, the DA* 200 f2.8, or the DA* 300 f4. Those lenses, to be sure, are quite expensive. But if you want resolution on the long end of things, you’re going to have to shell out big bucks for it.