So here is a quick test I do to see if it is time give the sensor a cleaning:
- Take a well-exposed shot of something light colored, a painted wall or the sky works well for me. I want to use a high f-stop, usually f/18 or so, so it needs to be a bright enough scene and I will use Aperture Priority mode. I don't crank up the ISO, leaving it at 100 or 200.
- Make sure your shot is in focus, and shoot a few.
Here is my test shot - I could have overexposed it a little to make it lighter, but that wasn't really necessary. Notice that the sensor spots are no very obvious (See it larger here Dirty Sensor Test-Unprocessed):
|Dirty Test Shot - Unprocessed|
Developing to bring them out in Lightroom is not very difficult. I like to convert to black and white then boost the contrast - especially in the middle range. Here is the result of my develop changes for this same image (See it larger here Dirty Sensor Test - Processed):
|Dirty Sensor Test Shot : Processed|
I know that on this blog post, the spots may not look obvious in the relatively small JPEG, but if you do this in Lightroom, then Zoom in 100% and pan around your image, the dust spots will be pretty easy to see.
For reference, here is what the Develop Module settings I used. I also save these as a User Preset in Lightroom so I can do this test with very little effort in the future. I have also exported these settings so they may be imported as a User preset into Lightroom. Get that file here: Lightroom Dirty Sensor Test - Sky