smc Pentax-M* 300mm f/4
Welcome to next round of this exploratory journey into the realm of digital photography with manual focus lenses. The goal is to highlight a technique, lens, camera, film, or subject in three frames. I have a lot of lenses, probably too many, so I'm going to focus in the short term on cycling thru my collection and maybe discuss a little about my photography habits along the way.
As should be obvious by the graphic above, today's focus will be the Pentax M*300 f4, a compact telephoto lens from the late 70s and early 80s. The M-series was supposed to stand for "miniature" since most of the Ms are small compared to contemporaries, and very very small compared to their modern equivalents.
Size really was a driving force and a differentiator for this lens, as it could be for all telephoto lenses if size, weight, and portability are considered in the design. This lens is 825g and 132mm long (translated, 1.8# and 5.2in), and is the smallest and lightest 300mm lens Pentax ever made, edging out the nearly identical A* version by just a hair in the weight class. The previous 300mm f/4 lens that this one replaced was 20% heavier and 42% longer, so the new design saved quite a bit of bag space. The modern 300mm f/4 prime lens (the DA* version) shares similar to the older larger version, and therefore shows a similar disadvantage in weight and size. I have not been able to find another manual focus lens that registers f/4 maximum aperture at a lower weight or size.
Of course, there are manual focus f/5.6 lenses around that are smaller and/or lighter, but you're giving up one stop of light in return. These lenses might be 200g (1.3#) or so lighter and just a little shorter. The step UP from f/4 to f/2.8 is quite different story. The manual focus Pentax A* 300mm f/2.8 that was introduced 8-10 years after this M*300 lens is almost twice as long, and weighing in at just over six and a half pounds, it is 3.5 times heavier.
So the lesson here is that weight/size and lens speed are proportional and require consideration when looking for a telephoto lens.
Portraiture is not the first thing one thinks of when someone whips out a 300mm lens, but this shot shows that it can be done. It is true, though, that in crowds or during sporting events or stage performances, a decently fast 300mm can aid greatly in getting shots from the back row if you don't have a press pass. Here, we see the Kawai-master having just swam (yes, swam) to this rock to sit with his mom. We are at the Buffalo River, of course.