Today’s Question: You have mentioned a sensor loupe for checking the camera’s sensor for dust. Is this more effective than the method of taking a test photo of a blank surface? It seems the latter would clearly show where there is dust on the sensor.
Tim’s Quick Answer: My experience has been that a sensor loupe absolutely provides an advantage over capturing a test shot for evaluating whether there is dust or other blemishes on your camera’s sensor. I’m currently using the Carson SensorMag (https://amzn.to/2LDw4cQ), and find that by using this loupe I don’t need to capture test shots at all in order to be confident that my sensor is clean.
More Detail: With a loupe designed for viewing the sensor in your camera (well, really the filter on top of the sensor), you can get an illuminated and magnified view of the surface, so that you’re able to clearly see even tiny dust spots and other blemishes. I’ve found this to be much more convenient and effective than the method of capturing a test photo to check for dust.
The basic process of using a test capture for sensor dust involves photographing a non-detailed subject while moving the camera, with the lens aperture fully stopped down. You can then evaluate the resulting image for spots, and get your camera cleaned as needed based on this test.
I have found, however, that a sensor loupe streamlines this entire process. With a sensor loupe you get a magnifier and bright light in a single package. This enables you to clearly see the surface of the filter in front of your camera’s sensor. You can therefore simply use the loupe to check if you need to clean the sensor, and use it again to confirm you were successful at effectively cleaning all of the blemishes.
To me this workflow is much easier than the process of capturing a test photo, downloading that test photo to the computer for the best evaluation, and repeating that process potentially more than once to evaluate the effectiveness of your sensor cleaning.
As a result, I consider a sensor loupe (https://amzn.to/2LDw4cQ) to be one of the more critical tools in my camera bag.