>should
>be looking for a 100mm prime lens for the portrait lens, but I can't seem
>to
>find much on ebay. Actually none, except for some screw mounts. There
>are
>a lot of 135mm lenses. Would the do similar things?
The normal "portrait lens" range is 85-120mm, but a 135 might work for
some sorts of portraits. The issue is that a 50mm lens tends to produce a
little bit of "wide angle distortion" of features compared to what we are
used to, whereas the slightly longer focal length of 85-120 "compresses" the
relative size of the nose and ears back to what looks normal or attractive
to most people. For many many people an 85mm lens is the standard
portrait lens, rather than 100. Much longer than 105mm and you start to
get a portrait that some people see as unnaturally "compressed" in the
facial features.
If you are actually looking for a telephoto lens rather than a "portrait"
lens, I might recommend a 200mm instead. They are cheap and plentiful.
Pentax made a couple of 85s, all of which are a bit spendy and hard to
find, to wit:
85mm f/1.8 SMC ("K") which is very rare and sought after, thus expensive
and hard to find.
85mm f/1.4 A* and 85mm f/1.4 FA*, both very nice lenses but WAY too
expensive to cut your teeth on.
85mm f/2.0 M, which is small, light, and somewhat affordable. It has a
mediocre reputation, primarily due to a bit of softness at large
apertures. Depending on what your portrait preferences are, this may not
be an issue. This is the lens you are most likely to find on the market.
Pentax made a couple of 100/105s, all good, and also relatively expensive
and hard to find.
100mm f/2.8 M, which seems to go for about $175 in used camera shops and
has a good reputation.
105mm f/2.8 SMC ("K"), which is rare and sought after. I have not seen
one of these on the used market in a while.
100mm f/2.8 and f/4 macros, which have a good reputation but macros are
likely to be larger and more expensive than would be ideal for portrait
work, and by definition a macro lens is optimized to be equally sharp
across the field in one flat plane (so you can photograph stamps and the
like) which may well mean that theya are less well optimized for
portraiture of 3D objects at longer ranges.
Pentax made a couple of 120mm lenses, but I have never seen one on the
used market. I think they were designed for portraiture.
Given that the 135/3.5 M lens is cheap, good, and readily availible, it
might be a good alternative to finding or paying for one of the above.
Two 135s to avoid would be the 135/2.8 A and the Takumar Bayonet 135/2.5,
which have poor reputations. They might serve, but you can do better for not
much extra money.
>As far as the wide angle goes is it worth trying to hunt down a 24mm or
>is 28mm just as good?
As a novice, I'd steer you aggressively towards the 28. Optically, 28s
are better than 24s almost uniformly, plus they are substantially cheaper
and easier to find. I'd recommend the 28/3.5 M as the best choice for
"good and cheap". I find 24mm to be a bit of a challenge compositionally
because of the wide angle of view. You have to get very close to make
smaller subjects fill the frame, and perspective distortion is very easy
to achieve whether you want it or not. I have always had a 24mm or 20mm
lens in my bag, but I find the 28mm is still my standard wide-angle.
Mind you, 24 IS noticeably wider. Often, this is not a good thing until
and unless you know what to do with it.
DJE
