[a200user]

Has anyone successfully removed internal dust inside the front elements of a DA 18-250mm lens? This is the same lens as the Tamron AF 18-250mm Di II lens.

I've had mine for several years and there are a few annoying specs of dust that I can see on the inside of the front element and possibly on the outside of the second element.

Is there a way to access these from the front? I wouldn't want to have to disassemble from the back which I'm sure would then require specialized equipment.

I saw this videos for a different Tamron:

You Tube

You Tube

Has anyone tried this?

Here's another for a Tamron 17-50mm :

You Tube

You Tube

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Last edited by a200user; 06-09-2020 at 09:02 AM.

[Pentax Syntax]

The dust is unlikely to effect anything so I would advise just leaving it. It takes a lot of dust to do anything to image quality, particularly on those outer elements. I have tightened the outside screws on my Tamron 28-300 (the one shown in the linked video). The screws are small and hard to align. I also have the Pentax 18-250 and the screws are also quite small. Very real risk of stripping the screws on either lens. If the lens is working properly I would just leave it with a few dust particles.

[Bertrand3000]

I have also some dust inside my Tamron 18-250. It has no effect on IQ.

[a200user]

I guess I'm OCD about the dust, and being bored with not much to do because of the Coronavirus shutdown I decided to take the first 2 steps of dismantling the front element.

This video is closer to how my lens is assembled than the other 2 videos in my first post above.

You Tube

You Tube

The front element holder in this video has 'calibration' holes, however on mine there are no distinct holes, just continuous slots so you have to mark the screw locations on the element holder exactly before removing the screws. So I went ahead and did the entire job. It was an easy procedure. I checked the focus after putting it back together and it's right where it originally was.
To me the greatest risk is not marking the location of where the screws go. The mounting holes for the front element holder are on a series of 'wedges' around the circumference of where the front element attaches. this will vary the distance between the front element and the next element which of course effects focus. From what I understand specialized calibration equipment is used to set the exact location, so it is most important to get the front element mounted in the exact location from where it is removed from.

[Pentax Syntax]

Ah good that it worked out. Yes marking where the screws go would be difficult. I was concerned about getting the wedges to sit properly. Thanks for the video and update.

[longbo]

I guess I'm OCD about the dust, and being bored with not much to do because of the Coronavirus shutdown I decided to take the first 2 steps of dismantling the front element.

This video is closer to how my lens is assembled than the other 2 videos in my first post above.
Tamron 17-50mm f/2.8 XR Di-II VC cleaning the lens inside - YouTube

The front element holder in this video has 'calibration' holes, however on mine there are no distinct holes, just continuous slots so you have to mark the screw locations on the element holder exactly before removing the screws. So I went ahead and did the entire job. It was an easy procedure. I checked the focus after putting it back together and it's right where it originally was.
To me the greatest risk is not marking the location of where the screws go. The mounting holes for the front element holder are on a series of 'wedges' around the circumference of where the front element attaches. this will vary the distance between the front element and the next element which of course effects focus. From what I understand specialized calibration equipment is used to set the exact location, so it is most important to get the front element mounted in the exact location from where it is removed from.

Thanks for this excellent video. I have this lens and there's a lump of something inside the rear optic. Do you have anything about removing the rear optic to clean inside? I'm wary about moving the spring contacts.