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12-20-2011, 10:41 PM   #1
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Question to DA 18-135 owners: internal anti-reflective coating?

Hello,

I recently purchased a DA 18-135 and am very pleased with it. With my K200D, it's a great combination. I'm concerned about one thing however. When looking into the lens through the front element, with the lens extended to 135mm, on what appears to be the intermediate barrel surrounding the internal lens elements are a multitude of white or silver speckles. I can't tell if this is some kind of dust from manufacturing, or if it's the particular type of coating applied to the inside to reduce reflections. I'm used to seeing only a black matte finish inside of lens barrels so this appears very strange to me. I would be curious to hear from anyone else with this lens if they see the same thing inside theirs. If everyone sees the same, I'll assume it's the type of coating. If not, I guess I'll have to send it to service for cleaning under warranty.

Thanks, BobG

12-20-2011, 11:24 PM   #2
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Yep, its there on mine too. After the first barrel with ridges comes a short barrel that looks like a dust magnet....maybe 100 reflective spots. Does not appear to be that level of dust on the elements so I assume its part of the design. Certainly unlike my other zooms.
12-21-2011, 12:27 AM   #3
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Maybe Pentax's "Super protect" coating that's making an illusion?

Adam
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12-21-2011, 05:24 AM   #4
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Hadn't noticed that until looking because of your post. The specs only appear on the innermost components and not on other pieces from what I can see. They appear to be integral to the construction material from my view and not 'sitting' on the material. No movements dislodge them.

12-21-2011, 07:07 AM   #5
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Appreciate the responses. To imtheguy, your observation matches mine regarding the number of reflective spots surrounding the element. The element at that location however appears clean. I bought this lens for a trip overseas tomorrow. I stupidly waited until the last minute to purchase it so there's no time to exchange it through the vendor if need be. I've planned on this being the only lens I use during my trip so I really freaked out when I noticed this.
12-21-2011, 07:44 AM   #6
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QuoteOriginally posted by BobG Quote
Appreciate the responses. To imtheguy, your observation matches mine regarding the number of reflective spots surrounding the element. The element at that location however appears clean. I bought this lens for a trip overseas tomorrow. I stupidly waited until the last minute to purchase it so there's no time to exchange it through the vendor if need be. I've planned on this being the only lens I use during my trip so I really freaked out when I noticed this.
Perfectly understandable given the situation. It is unique in my experience. Perhaps it has to do with the water resistance but why on the interior? More likely a new material that resists deforming due to stress/heat/etc. Have a great trip and bring back some photos for us to see how well your 18-135 did!
12-21-2011, 09:39 AM   #7
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I checked mine (bought from forum member here) and it looked exactly as what you have described. That small section of wall in the inside barrel (only when the lens is extended to 135mm) looks like it is made from a different material with the speckles as you described. I also noticed that it is rather uniformly spaced and only visible from certain angle.

Anyway, I am very happy with the lens so far. Given the high iso performance of the k-5, this lens is a great complement to the k-5 as a light travel lens. I don't think you have to worry about the lens, enjoy your trip and your photography.
12-21-2011, 10:37 AM   #8
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Just want to clarify that we're all looking at the same thing. Where I primarily see it is on the surfaces directly surrounding the element (where the element is supported), not further out on the vertical interior walls of the barrel. That's what really concerned me, that it's right adjacent to the lens. I don't have to hold the lens on any particular angle to see it, just zoom out, look in and there it is. I've never seen an internal coating like this. If light is reflected back out from these specks making them visible, is it causing light to bounce around inside the lens assembly affecting image quality?

Thanks.

12-22-2011, 05:35 PM   #9
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My lens has the same specks you describe.
IQ of the lens seems unaffected one way or the other.
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