Too much dust inside the inner lens of an Oly 12-40 f2.8 Pro ?

Started 2 months ago | Discussions thread
OP martin_sc42 New Member • Posts: 12
Re: Too much dust inside the inner lens of an Oly 12-40 f2.8 Pro ?

cba_melbourne wrote:

The 12-40 is an external zoom. It changes it's length (or trombones) when zooming. This means it breathes in air as you expand it. The 12-40 is fitted with a mesh filter to keep out sand and coarse dust particles. But finest dust (as well as vapor and smoke) will obviously get through the mesh, and deposit on interior surfaces.

12-40 lens. The yellow bit is the filter mesh that goes around the barrel. It is just a very thin fine mesh, not something like a felt or a foam that could trap finest dust particles. I have seen somewhere a picture of that filter, but can't remember where.... sorry.

Thank's for sharing. That is my point. See also

When extending to 40mm and with some light into the front you can clearly see the Oly front chamber. In the diagram this chamber is closed to 12 mm.

If somehow something comes in via the airflow or even via the tube by slipping under the seals it should settle in the front chamber (front lens or back lens). If it somehow comes in from behind it should settle on the back chamber, maybe the moving inner zoom and focus elements. Yet the lens unit holding the aperture control is exactly in the middle. As it also is the smallest in diameter this amount of dust clearly should cost some sharpness.

I am no photo technician yet an tech engineer. Using a lab control LED you can see this when lightning from back to front as some of the lenses are coated on the back and when reflect some light like halo.

a) I see dust on the lens in the aperture control hole.
b) I see no dust on the lens more closer to the front (front chamber)
c) I see no dust on the inside of the front lens
Similar on the back

So weather sealing works. Even if i wanted to destroy a lens I have now idea how to achieve this effect without dismantling it

I would speculate a product defect in the aperture control

A rational explanation maybe that the aperture blades have some friction and distribute particles or similar.

I did not check this so strictly as i bought it 13 months ago ... grmpf ...

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