You don't really want to look inside any modern autofocus lens.
Compared to even the cheapest old "brass" and glass manual focus lens
they appear to be made of well the best was I can describe it is cheap
roughly finished stampings. The Japanese especially have a knack of
reducing the cost and making parts only as costly as they absolutely
have to be. Let's take two similar lenses, which I've partially
disassembled. a Vivitar 17-28mm rectilinear from the 1980's, and a
Pentax FA 20-35mm rectilinear. The internal parts of the Vivitar were
all metal, machined and cast very nicely finished, hand assembled and in
operation the zoom and focus rings turned as smooth as silk. The
Pentax, well except for a the gearing mostly plastic not rough finished
but not the smoothest either, the gearing for the autofocus is aparently
stainless steel and very nicely finished and pretty close fit, the rest
fit together nicely but still a bit loose. The zoom and focus rings
were nicely damped but the feel was plastic sliding on plastic, with the
focus ring sometimes eliciting a slight whirring sound from the metal
gearing. The difference, the Pentax focuses accurately at all focal
lengths, the Vivitar not so much, those lovely finished cast and
machined parts were made not of brass, but some kind of pot metal, that
was too easily deformed, so a few moderate knocks and the focus while
smooth made no apparent change in the viewfinder or on film, which was
why I took it apart. The Pentax by the way got some fine grit in it's
works, and I only took it apart enough to blow it out. Once reassembled
it works well to this day. I've partially disassembled a number of
autofocus lenses and really I don't want to know what's inside as long
as they work. They remind me of computer programs under the covers.
On 7/24/2013 8:35 AM, Zos Xavius wrote:
what did he say? why would we be insulted? if its poorly built, its
poorly built.
On Wed, Jul 24, 2013 at 7:40 AM, Boris Liberman <bori...@gmail.com> wrote:
One of local Pentaxians had 17-70/4. The SDM failed on him and being a
handy person he took it apart. I won't repeat what he told me so as
not to insult anyone. It was a very strong arguments against the SDM
lenses, at least the cheaper ones.
On Wed, Jul 24, 2013 at 2:27 PM, David J Brooks <pentko...@gmail.com> wrote:
Thanks for the comments so far. Given me some things to think about. I
have a fader ND filter at 67mm dia, so the Pentax 17-70 would fit it,
but leery of the SDM from what i have read previously. I don
t need IS as its in the K-5 body so that would be a wasted Sigma
feature. Decisions decisions.
Dave
On Wed, Jul 24, 2013 at 2:21 AM, Boris Liberman <bori...@gmail.com> wrote:
I concur. Although when I first saw the lens in your hands, Jaume, I
did not expect to own it some day. I should point that it is not that
heavy given the speed and zoom range. It is rather well made although
indeed eventually the zoom becomes creepy. It does have the zoom look
that is handy for transportation, obviously.
On Tue, Jul 23, 2013 at 9:49 PM, Jaume Lahuerta <jlah...@yahoo.com> wrote:
Hi,
I also have the old Sigma 17-70 (actually I think that I have some
responsibility in Boris owning one...) and I second Boris comments. The only
complaint is that is is a bit heavy and the zoom eventually becomes loose.
I have physically seen the latest version and I have to admit that it looks and
feels extremely compact.
However, my favorite compromise range / IQ would be the 18-135. Sigma has one
but its reputation is worst than the 17-70s and the Pentax one seems a bit
expensive.
Regards,
Jaume
----- Mensaje original -----
De: Boris Liberman <bori...@gmail.com>
Para: Pentax-Discuss Mail List <pdml@pdml.net>
CC:
Enviado: Martes 23 de julio de 2013 13:47
Asunto: Re: the 16-45 to 17-70 range
Dave, I've (the oldest version of) Sigma 17-70/2.8-4.5. Such lenses
can be had for order of USD 250-300. I cannot praise mine enough. It
successfully replaced DA* 16-50/2.8. Later versions are 17-70/2.8-4.0
(notice faster long end of the zoom range) and further introduced HSM
(Sigma's ultrasonic AF) and OS (Optical image Stabilization). I opted
out of these as I wanted something as simple as possible so that it
won't break down just because.
Optically I've no complaints at all. It just what suits me best right
now if and when I have to shoot with DSLR.
On Tue, Jul 23, 2013 at 2:40 PM, David J Brooks <pentko...@gmail.com>
wrote:
Hey all.
This last week at the plow demo got me thinking again about my short
zoom, the 16-45. Normally i take two cameras, the D2H with re 70-200
VR f2.8 and the D200 with the 18-70. I use the 18-70 for the closer
shots when the teams come at me. This year i took the K-5 and used the
16-45. It performed fine, but at 45 at the long end just does not get
what i want before i switch back to the longer zoom.
So
Im thinking something along the lines of the Pentax or Sigma 17-70 ish
lenses, and i think i saw on Henrys site an 18-135???
I know these have come up before just looking for opinions.
Also the 55-30 is still on my list, although the sales person at
Henreys showed me the Sigma version, a bit cheaper and now i'm humming
on that one.
Comments about the short zooms or the Sigma 55-300 appreciated,
Dave
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