Lens Spotlight: K105 - Jason Doss

Lens Spotlight

smc Pentax-K 105mm f/2.8


The Pentax SMC-K 105mm f/2.8 is a multipurpose short telephoto lens. Like all lenses in my collection, this one is fully manual with an aperture ring and manual focus ring. I picked it up bundled with the K105/2.8, which will be the subject of the next writeup.


Telephoto focal lengths are the next level up from normal focal lengths, and are typically divided into short telephotos, standard telephotos, and extreme telephotos.  The lines are blurry and not universally accepted, but to say "I have a short telephoto," would get your point across to most people.  100mm is a common focal length, and modern versions are almost always macro lenses.  In the olden days, there were typically 100mm macro lenses, and 100mm short teles used for portraits or general purpose.  I'm not sure why the difference, but presume size and weight had something to do with it since the macros are almost always larger.


The lens is 331g (0.73#) and, focused at infinity, 63mm long (2.5 inches) and has 6 aperture blades and 52mm filter threads. The fast aperture of f/2.8 is about average for normal lenses of the day, although some were considerably faster. The lens bears the usual aperture ring and has a rubberized grip for easy manual focusing. Minimum focus distance is 120cm (3.9ft) producing 1:9 reproduction ratio (0.11x), which is pretty good unassisted. Of course, extension tubes and diopters can greatly increase the magnification.



And so before you I present three photos from a recent weekend walkabout in the Harrison (Arkansas) city park.  While my lovely wife was shopping till she dropped, the boys and I were out absorbing UV radiation and counting particles of trash.  The park is a filthy place.  Then behold, a chopper came overhead (upper right), landed (below), then later on took off again (upper right).


This collection isn't necessarily impressive, but some skill in getting focus on a moving object on a blank background is required.  I felt the lens did a good job getting images, although some of the bokeh in the bottom image is a little uncomfortable... not as smooth as some would like.  Next go-round, I'll try some wide open shots.  Overall, not a remarkably challenging set of images, but I hope you like them anyway.



That's all I have for now... See you next time.


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