Originally posted by bobwired In the first 4 hours of use, the focus scratchiness has gone away.
Perhaps the lubricant had dried out or wasn't applied everywhere it needed to be.
Actually, I would guess it was plastic being smoothed out by mechanical use.
I.e., these lenses are mass produced, and it would not surprise me if the plastic molds have some slight "spillover" at some edges.
Those "edges" are then "sticking out" and after a little mechanical use, become "smoothed down."
No different than a car engine, edges get "smoothed out" within the first few uses.
Originally posted by bobwired The 18-55mm lens is very light weight compared to my old non-autofocus 40-80 f/2.8-4 macro zoom. The old zoom cost me $159 in 1980. Taking inflation into account, that's worth $440 in today's dollars. Probably not many people would pay that today!
The latest in plastic and polycarbonate material science combined with the latest manufacturing techniques, the fab is relatively new as I understand it.
You get lightweight, but fairly durable units at a very, very commodity cost.
The question then becomes, how good are the yields, and what QA measures are in place to determine the specifications and acceptable results?
My only, current complaint is that Pentax's (Tokina's as well?) QA specifications are too loose.
I.e., I've been "guestimating," based on reports from various boards, that about 20% or so DA units are barely "within specification."
I wish Pentax would tighten those specifications, reducing yield about 20% or so, but everyone would get a good sample.
I'd be willing to pay 25% more for that, especially since my DA 50-200 unit is outstanding in quality.
My DA 16-45 seems to be the same as well, and even my DA 18-55 was nothing to sneeze at.
But people are getting some faulty DA 18-55 units, and DA 50-200 units (PhotoZone.DE definitely got a bad, but "within specifications" DA 50-200 from their shots).
Originally posted by bobwired Maybe plastic lenses are OK, even if they aren't as durable? (and, the newer lens doesn't have to illuminate a full 36 x 24mm frame,)
Material science has drastically improved not just in the last decade, but even the last 5 years.
E.g., NASA shut down the X-33 project as the Shuttle Transport System (STS) replacement some 5 years ago because the carbon fiber cryogenic tanks failed, and they didn't think material science would solve the problem soon enough.
Well, they did last year, but the X-33 remains canceled (and Lockheed Martin's commercial VentureStar endeavor with it
.
Originally posted by bobwired Guess I'll have to take some pictures with both and see how they work.
The DA 18-55 seems to be consistently weak at the corners, a result of the design, not so much the fabrication.
The DA 16-45, on the other hand, seems to be outstanding, and even the limited CA issue doesn't result in purple fringing (PF).
And my DA 50-200 has been quite the performer, and I know others have seen similar with theirs, despite its size.