Dirt on camera's sensor

Yesterday I wrote about some dirt on the sensor of my camera that created heavy work in post-processing my photo. So I thought it would be interesting to you if I write a bit more about that dirt. If you own a DSLR camera and several lenses you probably change lenses from time to time, depending on what you want to capture. By dismounting the lens you make the inner parts of your camera vulnerable to dirt and dust. Especially if do it outdoors at windy conditions. But also at home your sensor can easily become dirty when changing lenses. I want to show it on two examples of unedited photos of mine. (You have to click on it to view it full resolution and see all the dirt.)

45mm  f/32  1/20sec  ISO100

Under "normal" conditions this doesn't matter. You won't see anything in your photo. Usually you or your camera choose aperture values lower than 16. Higher values are possible but they result in lightly blurred imaged due to refraction of light at aperture blades. But, if you really need extremely high values for apertures, higher than 20, then any dust particle will become visible in your photo. For instance, if you compare the first photo of my yesterday's post and the one above, you will notice the difference. They are shot with exactly the same gear at the same time and location, but with different aperture values. The photo above contains lots of dark spots. These are dust and dirt particles on your camera's sensor. In yesterday's photo they are not visible. Yesterday's second photo is the same as above, but with manually removed dust spots.

27mm  f/25  5sec  ISO100

In some occasions you cannot prevent extremely high aperture values. I for myself do not own any ND filter. To get lower shutter speeds, for instance to create motion blur, the only way to achieve this is to use very high aperture values. Another example for low shutter speed is taking photos of thunderstorm lightnings, like in the photo above. To increase the chance of capturing one lightning I usually try to let the shutter open as long as possible. To not overexpose the photo I have to select the highest possible aperture value. With the photo above I first was very happy to get a nice and clear lightning captured, but when reviewing it at my computer screen in high resolution I was immediately disappointed. I saw all these dark dirt spots that have ruined the shot completely. You can try to remove them in post-processing, but this will be a lot of work.

If you don't own a camera with changeable lenses or if you don't change lens, this will hopefully not apply to you. But otherwise keep in mind that very high aperture values will bring any dirt on your camera's sensor to attention. What I did, after seeing all the dirt in the recent shots, was to bring my camera to a local photography store to let the sensor cleaned. There are lots of instruction for doing it yourself in the Internet, but I am happier when it is done by a skilled professional.