[everydaylife]

How much dust is acceptable in a brand new fresh out of the factory never been used weather sealed lens? Is there a permissable amount say 10 specks before they it fails QC. I ask this because my new lens has several specks of dust inside. Could it be a sign of failure of the weather sealing.

If I was buying this lens used and it had this amount of dust inside I wouldn't care but here in Japan I that if a used ens has dust inside but is perfect in every other respect it would not be listed as mint condition and would be priced as such.

So the question is this. Should a brand spanking new weather sealed lens that cost a fortune have dust inside fresh out of the factory and if it does have dust after owning it for 3 days and shooting with it twice do I suspect that the weather sealing has failed return it and ask for another copy??

[Na Horuk]

Its kind of hard for us to judge without seeing it. Maybe show a photo? Are you sure its dust inside and not just stuff on the front/back element or on the camera sensor?
Also, if you put the aperture to f22 take a bright shot of the sky, do the dust specs show up?
I dunno, if you bought it at a store you might want to go back and ask the salesperson, have them show you another copy and if it looks better, ask them for an exchange.

[everydaylife]

Na Horuk;2299100]I Are you sure its dust inside and not just stuff on the front/back element or on the camera sensor?

I know because I shone a strong light into the lens and it is obviously on internal elements. The dust will not show up in an image. This is a tele lens so I doubt I would ever use it at apertures at which the dust would be visible and it probably wouldn't even at its smallest aperture. I have read countless times that dust inside a lens has little effect on image quality and as I said if it was used I wouldn't care. Whether the dust will be visible in an image is irrelevant. It is that this new lens is sealed against dust yet it has dust inside.

Actually dust inside a lens can effect image quality in that it can reduce the contrast of a lens which in turn has an affect on apparent sharpness.

[VisualDarkness]

That sounds about normal as all WR lenses I've encountered had about that amount. It seems to be about the same with Canon and Nikon too from what I've read but maybe makers like Leica and Hasselblad is less tolerant of dust in the production?

[Eulogy]

This would really depend on the lens. If it's internal zooming/focusing, no dust should ever be apparent. If it's an external zoomer, then dust can still get in and out via the rear mount.

[Laurentiu Cristofor]

How much dust is acceptable in a brand new fresh out of the factory never been used weather sealed lens? Is there a permissable amount say 10 specks before they it fails QC.

It would help to specify the lens model.

My first copy of the Zeiss 85/1.4 came with tons of dust under the front element. I sent it back for a replacement and got a new one that still had a dozen specks. I contacted Zeiss and they told me that the design of the 85mm (large front element) can make it easier to notice dust (which still didn't explain the difference in dust between the two samples I had examined) and that they don't get their lenses assembled in dust free facilities (which was curious because I never had any dust issue with Voigtlander lenses, also made by Cosina). I still don't know if the first copy was dusty because of the manufacturing process or because of some other reason. And I was surprised that they weren't very surprised about the issue.

Based on this experience, it certainly doesn't sound that dust is a QC criteria.

[VisualDarkness]

I worked a while in a precision industrial machine factory and they actually decided to vacuum and clean the most of the factory for the first time in 20(!) years when I was there. The assembly plant was considered a clean facility but after some reports of failed seals and gears that may have been due to dust and dirt they begun the cleaning. All I can say is that machines and workbench lighting covered with a thick layer of dust, dirt and grease often is considered "clean" when it comes to assembly plants.

I guess that lenses aren't made in laboratory sterile environments either and I even doubt that expensive hand-assembled lenses are made inside protected dust proof boxes (the ones you only stick your hands through.

[everydaylife]

It would help to specify the lens model.

.

The lens is DA* 200mm and infact it is my third copy. First was great but had an aperture problem so exchanged at place of purchase. Second copy had an inconsistant focus problem and after 3 weeks Pentax returned it stating it was fine. 4 days later the lens completely stopped focusing. Pentax kindly agreed to exchange it rather than repair it. This third copy that I collected last friday has dreadful color and contrast in comparison to the other copies, and after further inspecting it just now I find that not only is there internal dust but marks on the rear element. Dust or grease I do not know but how those marks have got there ????

[interested_observer]

The lens is DA* 200mm and infact it is my third copy. First was great but had an aperture problem so exchanged at place of purchase. Second copy had an inconsistant focus problem and after 3 weeks Pentax returned it stating it was fine. 4 days later the lens completely stopped focusing. Pentax kindly agreed to exchange it rather than repair it. This third copy that I collected last friday has dreadful color and contrast in comparison to the other copies, and after further inspecting it just now I find that not only is there internal dust but marks on the rear element. Dust or grease I do not know but how those marks have got there ????

#4 is the charm?

[Laurentiu Cristofor]

The lens is DA* 200mm and infact it is my third copy. First was great but had an aperture problem so exchanged at place of purchase. Second copy had an inconsistant focus problem and after 3 weeks Pentax returned it stating it was fine. 4 days later the lens completely stopped focusing. Pentax kindly agreed to exchange it rather than repair it. This third copy that I collected last friday has dreadful color and contrast in comparison to the other copies, and after further inspecting it just now I find that not only is there internal dust but marks on the rear element. Dust or grease I do not know but how those marks have got there ????

In the words of Ash (from Alien, not Pentax Forums):

I can't lie to you about your chances, but... you have my sympathies.

I went through three DA* 300 lenses before giving up on that lens, but my problems were due to damage during shipping. It is very frustrating to have such experience with products that are so expensive. With the lack of box seals, I always wonder whether they've been used, returned, refurbished or whatever. A $60 video game comes in a sealed package and a $1000+ lens comes in a thin cardboard box wrapped in a plastic bag. Ironic, isn't it?

Good luck with your next try or with the return, whichever you choose!

[everydaylife]

I have no chance of getting a refund so I am stuck with repairs. I live close to Pentax service center so it is no trouble for me to call in to see what they have to say. The first thing they did was point out that it is not a good idea to shine a strong white neon light into a lens simply because all lenses have dust and the light will make it flare so as far as they are concerned the dust is no problem but they have kept the body and the lens to check regarding weak contrast and color. After all it could be a body problem as opposed to a lens problem.

[Laurentiu Cristofor]

The first thing they did was point out that it is not a good idea to shine a strong white neon light into a lens simply because all lenses have dust and the light will make it flare

I check dust by looking through the lens at a lamp, so the light is shaded. I don't see much dust in new lenses, but it starts to show after some use. Very fine dust is not a problem - if everything else looks good, I would not be worried.