To see how much dust you have on your DSLR's sensor: first, photograph a pale/white, untextured and evenly lit surface (for example a sheet of paper). Focus to infinity. Set the aperture to as small as you can (for example f/22). Set exposure compensation to +2.

This is how a sensor can look like after a thorough blower cleaning (without any post processing):

A blower is the standard method of cleaning a sensor. It's an easy and a safe way and it will remove the bigger particles from the sensor, when you use the blower correctly. You should use the blower in a dust free environment and try to keep the blower itself clean. Hold the camera upside down, clean the mirror box first with the blower and then the sensor. Do NOT touch the sensor with anything! Do NOT breathe/blow breath to the sensor. Do NOT use compressed air (from a can) directly to the sensor.

The blower does not work flawlessly. It will not remove dirt that is stuck. There are tons of websites to see for information on sensor cleaning. The "wet" method of cleaning - so called "Copper hill" method (described here: https://pbase.com/copperhill/ccd_cleaning ) combined with a blower is what I use myself. Basically, in the wet method, you use a small rubber spatula of appropriate size, wrap it with non-scratching tissue that doesn't shed dust (Like PecPads - search the net), apply a VERY small amount of pure alcohol (a few drops) on the tissue and sweep the sensor with it. I think it is wise to use the blower first, before sweeping the sensor. For complete instructions on wet-sweeping the sensor, see the Copper hill web site.

Without making adjustments to the test image, you can't see whether the sensor is clean or not. To see if the sensor is truly clean, make a levels adjustment similar to the one below



...to bring out the dust:



People use either isopropylalcohol or methanol to clean the sensor. Be told, that methanol is highly toxic (it will blind/kill you if you drink it). So don't play with the stuff. Methanol is supposed to be better for cleaning the sensor, because it evaporates more quicly than isopropylalcohol. This is also, why it's not a good idea to breethe above the bottle too deeply. You should use as pure alchol as possible (like 99,8% pure methanol) for the sensor cleaning.

Some people use medical swabs to sweep the sensor, but I have to say, that the ones I've tried leave too many fabric particles on the sensor - they are not tightly woven enough to be used. The medical swabs can leave more stuff to the sensor than you cleaned.

Below is an image that has been taken after sweeping with methanol. Some particles have been detached from the swab to the sensor:



It is inevitable that some dust will form on the sensor. Even if you alway use one lens and never take it off. The lens attachment is not that tigh. The more you change lenses and the more dusty the place you shoot, the more dust you'll get. Dust is everywhere - just look at the livingroom air in a beam of sunlight. Sometimes, there is dust on the sensor, when you have just bought it and opened the package.

On the other hand, dust is not something you have to get excited about - if you see enough in your pictures for the dust to be disturbing, THEN worry about it... :)

Also remember. when you shoot at large apertures and use little post processing (increasing contrast), the dust won't bother much. But when you shoot bright / even backrounds with small apertures (landscapes, sky, macros) and increase contrast in post processing, the dust will show more easily.

To put everything in perspective, below is a sample of an ordinary image, that has been subjected to the amount of levels correction, that is used to bring out dust on a sensor. It just shows you, that it takes a lot of contrast tweaking to bring out a tiny amount of dust. Small amounts of dust on the sensor won't trouble you at all.

Disregard the thumbnail below. It's there just for the reason, that this page won't show without any pictures in the folder.