Dark specks drifting in Live View bokeh on a Canon Rebel T7 — sensor dust or dust inside the lens?
Asked 3/1/2022
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2 answers
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While using Live View on a Canon Rebel T7 with the EF 50mm f/1.8 STM, I noticed a dark speck that seemed to float around when I changed focus while photographing out-of-focus Christmas lights. It was most obvious with the lens wide open at f/1.8, where each light became a large blur circle. I also saw a few more specks in other parts of the frame.
I first suspected dust inside the lens, because I could see some particles in the lens and I didn’t notice the issue through the viewfinder. But later testing showed the same specks with my 18-55mm kit lens as well, and the dust pattern had shifted slightly.
Can dust on the sensor cause moving dark spots in Live View and out-of-focus highlights like this, and is sensor cleaning the right fix?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
4y ago
2 Answers
3
Not to worry, the speck is the shadow of a bit of dust on the protective cover glass that hovers over the digital image sensor. Digital cameras that allow lens removal and replacement exposure the image sensor during the interchange. In other words, dust and other contaminates frequently find their way inside and settle on the sensor cover glass. Such contaminates block light thus their shadow shows up as a dark artifact.
Your countermeasure is to clean the surface of the cover glass. This is a delicate operation that will require you to procure the customary tools. You should now search photo sites on the web and research sensor cleaning. You can do this but first you need to learn the techniques for this task.
More serious, if I am wrong, it could be a dead photo site. This is a pixel on the sensor that not reacting to light. No remedy for this.
Originally by user44949. Source · Licensed CC BY-SA 4.0
user44949
4y ago
0
Generated from our catalog & community — verify before relying on it.
Yes — the most likely cause is dust on the sensor’s cover glass, not dust inside the lens. Interchangeable-lens cameras often get sensor dust during lens changes, and those particles can appear as dark artifacts in Live View because Live View uses the imaging sensor directly.
Dust inside a lens usually has little visible effect on normal photos, and disassembling a lens is generally not worth the risk unless a repair tech does it.
Since you later saw the same specks with another lens, that strongly points to sensor dust rather than lens dust. If the dust pattern also changed, that supports the same conclusion.
The practical fix is to clean the sensor cover glass. Start by researching proper sensor-cleaning technique and using the correct tools; it’s a delicate job, but many photographers do it successfully. If you’re not comfortable, have it professionally cleaned.
A dead pixel is another possibility in principle, but based on your follow-up, sensor dust is the better fit here.
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