Digital Photography’s bug-bear!
When you change lenses there’s a chance that dust can enter your camera and land on your sensor.
It’s not going to kill your camera, but it will give you little black marks all over your photographs, which become very obvious on shots of skies.
I got my biggest ever dust spot at Kirkstall Abbey the other day, so thought it a good opportunity to show you it…. it’s a monster!
I thought it was a bird in one shot, but it was actually a little bit of a flower that had blown in when I changed lens. There are also many other blobs around if you look.
How to test for dust
So to test your sensor for dirt you can do this:-
- Set your camera to Av (Aperture priority) mode
- Set the aperture to the smallest setting – F22, F35, whatever it goes to.
- Put the Exposure compensation to +2
- Switch the auto-focus off and twist the focus ring to the nearest point
- Point the camera at a plain surface, a cloudless sky, pure white paper or something like that.
- Take a shot.
That will give you a bright exposure with any dots standing out “like a sore thumb” as they do on the shots above.
Damn, I’ve got dust!
Chances are you will have some dust from the experiment above, so do you pack up and go home?
Well no, dust is more apparent at smaller apertures, so becomes a real problem at F11 and smaller, but at wide apertures, F1.8, F2.8, F4 etc. it just seems to disappear.
Here’s pretty much the same shot as above, but at F1.8 – note that you can still see the “monster” blob, but the rest have disappeared.
How do I get rid of dust
Many modern cameras have an anti-static self clean function now, so it may not be such an issue.
You can get it done professionally, many camera fairs and events have stalls where they do it, or a quick google will find people who do it.
I use the Arctic Butterfly which uses a little spinning brush to create static, then you lightly pass it over your sensor, the static attracts the dust to the brush and you get a dust-free sensor.
If things are properly stuck on to the sensor, DO NOT try to rub them free with the butterfly, you’ll scratch your sensor and need an expensive repair.
Instead, use a “sensor swab” – these are wetted with some fluid and look like those things you glued stuff with at primary school – spatulas? These are a few quid each, so can get pricey if you use them constantly – hence going for the Arctic Butterfly.
Sensor dust is a pain, one which you need to monitor whilst shooting – imagine a wedding shoot with 1000 shots, each with a dust blob in the middle… keep an eye out, adapt the aperture if it’s a problem, and better still, give it a quick clean !