So you're on a trip and while reviewing your images you notice a bunch of dust spots. How they got there you don't know, but what you do know is that you've left your essential cleaning supplies (blower, sensor swabs, cleaning fluid etc.) at home. There are no camera stores within 100 miles that carry any of that stuff. What do you do?
Well, that was me a couple of weeks ago. I did have my "camera tool kit" with me, which includes a 5x loupe and a small LED flashlight (along with a bunch of small screwdrivers, tweezers and other tools), but nothing really suitable for sensor cleaning. Here's what the sensor looked like with a lens set to f22:
As you can see, lots of pretty visible dust spots. At normal shooting apertures they were less visisble, but still visible enough to need to be cloned out, even at f8. So what to do. Well, I thought back to my own article on using a sensor brush. I didn't have a brush with me, but all I really needed was a brush with very soft bristles, such as a small makeup brush or even a small paint brush. I found such a brush in a local drug store. Maybe not ideal, but the bristles were soft. If you don't have a loupe or LED flashlight with you, you might even find them in a local drugstore too.
I thoroughly cleaned the brush using soap and water and dried it using a hair drier. Then I took the 5x loupe and looked at the sensor while illuminating it from the side using the miniature LED flashlight. The dust spots and small hairs were quite visible once I adjusted the angle of viewing and illumination correctly. The schematic is shown below:
Then, with a minimum of pressure, I used the brush either to pick up or sweep to the side, the individual dust spots. If the brush has any static charge it will lift the tiny dust spots off the sensor). This took a few minutes. After I removed all of the visible spots I took another reference image (f22, defocused lens) and that image is shown below:
As you can see, the sensor is now much cleaner. There are a few faint dust spots, but they are pretty hard to see at f22 and at f8 they'd be just about invisible. Even with the dust spots as shown, unless the subject was uniform in tone, they probably not be visible in a normal image at all.
Without the loupe to identify the dust spots, it would probably have been difficult to get the sensor clean. I'd have had to try to brush the whole sensor, I'd have had to apply a little more pressure, and I wouldn't have been able to tell if I was adding more dust than I was removing except by taking a lot of test images. This way, using the loupe and LED, the contact between the brush and sensor was minimized, minimizing any chance of sensor damage or doing more harm than good!.
So if you're stuck in the boonies with a dirty sensor and no cleaning kit, remember that it's not impossible to safely clean the sensor using only basic tools. Of course if you have to hold the loupe, LED and brush at the same time, it helps to have three hands! I used what is sometimes called a "watchmaker loupe" which fits in your eye rather like a monocle, so that leaves one hand for the LED and the other for the brush! You can also find (see below) a loupe with an attached LED, though that only illuminates from one angle (pretty much head-on) and sometimes it may be easier to see the dust with the light coming in from the side.
The Delkin Devices DDSS-SCOPE2 shown above is a loupe designed for sensor inspection which has a built in LED source, but I'm not sure that you can get a brush in there too to remove the dust while you are looking at it. The System includes the Sensor Scope, 24 Sensor wands in 3 sizes, Sensor Vacuum (with USB Battery pack), 05 oz Sensor Solution, Carrying Case and Cleaning Guide