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Silver spots in 8514is this dust

G

grumpoid

Well-Known Member
Hi,

I have an 85/1.4 with what appears to be a fair amount of dust inside, only looking through the front optic, 3 of these 'specks of dust' shine a bright silver, almost like tiny stars...is this dust or could it be something else? they do look dark when viewed through the rear optic. Also, how much affect, if any could a fair amount of dust have on images? and how much may it cost for an internal clean in the UK?

Cheers for any help..Steve.
 
Hi Steve,

If these 'bright stars' are simply dust and not damage to the optical coating, then try Sendean Cameras (yes, them again) who would probably be able to get it checked out and cleaned. They can however repair coatings on lenses - that can be pretty pricey. You are probably looking at just over £100 for a clean up and recalibration - call or email them, they may give you a very rough estimate before seeing the lens.

They did work miracles on a 300 f4 with damage to an internal element. Have you tried the 85 on a digital camera to check the impact of the dust specks? I've done just that with an 85 1.2 I'm about to sell - it's got 3 dust particles near the rear element. Popped it onto the Olympus - no effect on the piccie, much to my relief.

Cheers. Graham
 
These "specks of dust" "bright stars" are strong reflections from very small points scattered around inside the lens elements. When you inspect the lens under the microscope you will see that these are bubbles inside the lens elements. The presence of these bubbles contributes to the formation of flare and halo. They also causes a reduction of the resolution of fine details and contrast of large scale and hence a depression of the curves in the MTF graph.

When I look at my lenses for these bubbles, the cheaper Zeiss lenses tend to have more. My C-Y 85 1.4 has a lot more of these bubbles than my 85 1.2. My 85 1.2 has these bubbles but they are a lot smaller.

I took some photos of these bubbles in my 45 2.8. You could see them in this forum.

http://www.contaxinfo.com/cgi-bin/discus/board-auth.cgi?file=/14022/530.html
 
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