Can fine dust in a lens make autofocus stick, and can I clean it myself?
Asked 6/7/2019
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2 answers
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My Sigma 18-250mm f/3.5-6.3 DC Macro OS for Nikon started making unusual autofocus noises after exposure to very fine sand/dust. Since then, autofocus often sticks unless I nudge the focus mechanism manually. Is there any safe way to clear dust from inside the lens or focus motor, or does it need professional service?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
4
Here’s what I did in the end:
First of all, opening up the lens is not a good idea. It’s a complex and delicate system, and if you don’t have experience in this area, avoid disassembling the lens.
To clear up the dust from within the focus ring you need to blow air from under it. In this model, this was not possible from outside. So I got a power duster spray, put the zoom to max (250mm in this case), and blew the air through the exposed parts of the inside of the lens, particularly behind the yellow cable.
I think I got almost all the dust out, and the lens is working fine now. But please note that the amount of dust was not a lot, and it didn’t really compare with lenses damaged from color runs.
Originally by user85198. Source · Licensed CC BY-SA 4.0
user85198
7y ago
0
Generated from our catalog & community — verify before relying on it.
Fine dust can absolutely cause autofocus problems by getting into the lens’s moving parts. In general, autofocus motors and lens internals are not user-serviceable, so the safest recommendation is to send the lens to Sigma or an authorized repair center.
Opening the lens yourself is not advised unless you already have repair experience, because the internal mechanisms are delicate and easy to damage or misalign.
One community report said they improved the same lens by not disassembling it, but by extending the zoom fully and using a powered air duster to blow through exposed internal gaps. That may help if the dust is light and only lodged near the focus/zoom mechanism. However, it is not guaranteed, and forcing air into the lens can also move dust deeper inside.
So the practical answer is:
- don’t open the lens yourself
- professional cleaning/repair is the proper fix
- at most, try very cautious external dusting/blowing only if the contamination seems minor
If autofocus is already sticking and making noise, service is the most reliable option.
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UniqueBot
AI7y ago
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