This is on a Canon 550.
I have seen this before on a Canon 350 and despite having a sensor cleaning kit I couldn't fix it.
Any ideas?
Also how to prevent it?
Sensor crud falls into 5 categories:
1. Dust, appears as specks. Can be dislodged with a rocket blower in most cases.
2. Oil spots, appears as a small rounded blob. Sometimes you can clean it with a swab and cleaning solution.
3. Glue/stick residue can appear as an irregular blob. Comes from improper use of a glue stick to remove dust. Cleaning solution and swabs won't touch it, use swabs sprayed with
https://www.amazon.com/ROR-Optical-Cleaner-Spray-Bottle/dp/B0002HMRF2
4. Grease spot, appears as an irregular blob. Most cleaning solutions won't touch it. Use swabs sprayed with
https://www.amazon.com/ROR-Optical-Cleaner-Spray-Bottle/dp/B0002HMRF2
5. Hair/fiber etc. appears as your example. I would advise holding the camera pointed down and using the rocket blower to dislodge it. Under no circumstances should you use Qtips or other types of cotton pads. Charges in the sensor can cause fibers to stick to the sensor. If you use a swab with wet solution, use a firm pressure and only go one way. Flip the swab over make another pass, then throw the swab away.
In a pinch if I didn't have ROR fluid I've used Denatured Alcohol for the tough jobs.
How to prevent it:
1. Always change lenses with the camera body pointed down, so that anything dislodged will hopefully fall out.
2. Don't change lenses in dusty or windy conditions outside.
3. Make it practice to periodically use a Rocket Blower (with the camera body upside down), to dislodge stray dust/fibers before they land on the sensor.