Hi, I have searched the archives on this and don't see it mentioned; I have just moved up to medium-format from 35mm and noticed the new pentax 105m lens that came with the kit in promo now has a notable piece of dust on the interior of the bottom of the lens. I have put a test roll in for devolopment but wont have back for a few days; Is this reasonable/normal (I have never seen dust inside any other lens I have owned), should i wait to see if it is visible on results or going ahead and see about exchanging?

Thanks,

Randall

-- randall thomas (dogfooddog@aol.com), November 21, 2001

Answers

Although it is quite common to have dust in new lenses, there is no excuse for it by the manufacturers. It is simply a lack of attention to detail. I once worked in a clean room environment(NASA) and can assure you that it is entirely possible to have dust free lens(at least not any particles that the eye can see). I don't think Pentax finds the dust problem an issue. A friend of mine had to return a Pentax lens because the dust was large and plentiful. The reason I don't like dust inside a lens is that it causes diffraction. But, a little dust doesn't really bother me.

-- Steve Rasmussen (srasmuss@flash.net), November 25, 2001.

Joachim, this situation has gotten worse with the 67 lenses. I have stated before in this forum that the older Super Takumar and Takumar lenses were of better quality than the recent Pentax ones. The 105mm comes to mind. I've had some problem with the mount area on my zoom and a couple of others. It was not so bad that I had to return them however. I have wondered about Pentax's process variability in their machining operation for some time. I own two Leica SLRs and they have perfect lens mount to lens fit. Pentax is crude in comparison. I own two screw mount Pentax lenses(35mm) from years ago and the build quality is really good compared with the newer 6x7 lenses. Pentax needs to start using Statistical Process Control on their machining before they lose customers! The contaminated glass is a disgrace! Not only did the producer(Hoya?)make the bad glass but Pentax accepted it into their plant and ground it. Obviously, there was no visual inspection by Pentax at the end of polishing. An unacceptable situation.

-- Steve Rasmussen (srasmuss@flash.net), March 05, 2002.

I would say that this is unacceptable for any new lens from any manufacturer. On an older lens, especially one purchases at a discount this would be acceptable and would contribute very little image degradation of sharpness, but I wouldn't accept it in a new lens....

Ed

-- Ed Hoey (ehoey@charter.net), November 21, 2001.

Let me begin by saying that you would have to pry my 6x7 equipment from my dead hands.

That said, I don't know that I have a lens that DOESN'T have some residual dust in it.

-- Rolf Strasheim (rolfs@thelunatech.com), November 21, 2001.

Pentax 67, Mamiya 7, Nikon, Zeiss....all of them I've found at least some measure of dust in them.

-- Scott Laughlin (scottlaughlin@mindspring.com), November 21, 2001.

I wouldn't worry about it. Almost all lenses have some dust in them. It won't effect picture quality unless it is very big or there are a lot of small pieces of dust

-- rolland elliott (rolland_elliott@hotmail.com), November 24, 2001.

Unfortunately, inadequate quality control becomes a frequent problem with Pentax 67 lenses: I just had to return two brand new 67 lenses because they had obvious flaws. The first (4/45mm) could not be mounted on the camera body without excessive force and a noise of scratching. The second (2.8/75mm) had a larger piece of dust (?) melted into the bottom lens element - and I am not talking about the usual dust particles found in every lens after a while. Adding the 2.8/90mm, which arrived with a piece of a fly (!) melted into the front lens element, I had to return three of my four Pentax 67 lenses. I never achieved a similar score in my 35mm days. Pentax really should consider the quality issue more seriously. While I finally always get the quality that I can expect at this price level, the transaction costs are really frustrating. By the way, this experience keeps me away from mail ordering - the trouble would be doubled.

-- Joachim Inkmann (Joachim.Inkmann@gmx.de), March 05, 2002.