I'd ignore the colors at this point since they don't seem to correspond
to aspheric or spherical elements. The front element doesn't seem to
separate I think it's a single piece of optical plastic, though a very
tough plastic since ie doesn't seem to scratch at all easily. I believe
the culprit is the second element from the right. I think the pink
colored elements are low dispersement glass.. I assume the green means a
completely plastic element. . The lens itself easily disassembles into
two parts. I took one of mine apart, the one where the element
separation eventually occurred, to clean some sand out of the works
originally, and later to try to determining if I'd gotten an internal
element dirty when said element began separate. When the separation is
well progressed it is easy to see, looks kind of like a large
cataract.Of course I could be completely wrong, but the separation
occurs in one of the rear groups.
Keith Whaley wrote:
P. J. Alling wrote:
That seems like a good price for it. It's life span is problematic
as the separation can happen while it's simply sitting on a shelf.
The problem was an aspheric element that was a spherical glass lens
molded into an optical plastic element with the same refraction
index. (It shows as one lens element in the optical formula
http://www.bdimitrov.de/kmp/lenses/zooms/_optics/28-70f4.gif ).
Which one? There are green, red and clear elements on that image.
Any chance it's the front-most (green) element?
Thibouille wrote:
Yeah I remember that and if I remember well, not easily repairable
by Pentax.
I wonder if at 50 Euros it would be worth the try r not.
I just got mine back from Pentax, and they charged a shade over US$80.
Of course, I don't know how long it will last, nor how good a job they
did. (That's one thing about film. Takes a while to get the results!
We get spoiled!)
However, Pentax did say what work was done, just not specifically.
Sort of like they replaced and repaired all necessary, tested focus
and zoom with an AF test body, tested the lens electronically, etc.
It's entirely possible they simply replaced that lens assembly with
off the shelf stock. You're not going to get much labor (time) out of
a $49.51 labor charge!
Nor, for that matter, much out of a parts charge of $26.66!
Ahhh well. I'll put a roll thru the camera and wring out the lens.
I don't yet have an interchangable lens DSLR, so it will HAVE to be film!
I would expect that if I don't subject the lens to extremes of
temperature, and avoid shock, it might last for a very long time!
On Sun, Jun 7, 2009 at 12:43 PM, Adam Maas<a...@mawz.ca> wrote:
The issue with this lens is that it's quite prone to unrepairable
element separation.
-Adam
Considering what I paid to have mine repaired/replaced, that's not
much of a big deal!
My original cost for this 99.9% perfect condition lens, and the
factory repair cost still adds up to less than $170 ~ and for a
useful, reportedly fine performing AF lens, that is CHEAP!
IMMHO! keith whaley
On Sun, Jun 7, 2009 at 4:24 AM, Thibouille <pentaxl...@gmail.com>
wrote:
I know this lens was well regarded in film era but what about its
digital performances?
Would it be worth chasing it?
What price would be acceptable for that lens ?
Thank you all.
--
Thibault Massart aka Thibouille
--
PDML Pentax-Discuss Mail List
PDML@pdml.net
http://pdml.net/mailman/listinfo/pdml_pdml.net
to UNSUBSCRIBE from the PDML, please visit the link directly above and
follow the directions.
--
--
The free man owns himself. He can damage himself with either eating or
drinking; he can ruin himself with gambling. If he does he is certainly a damn
fool, and he might possibly be a damned soul; but if he may not, he is not a
free man any more than a dog.
--G. K. Chesterton
--
PDML Pentax-Discuss Mail List
PDML@pdml.net
http://pdml.net/mailman/listinfo/pdml_pdml.net
to UNSUBSCRIBE from the PDML, please visit the link directly above and follow
the directions.
