In a few of my recent Ask Tim Grey eNewsletters I have addressed the subject of cleaning the sensor on a digital SLR camera. Part of that overall process involves evaluating the sensor (which really means evaluating the filter in front of the sensor) to see if there is any dust or other debris that needs to be cleaned.
One of the common approaches to checking for dust on a sensor is to capture a test photo of a blank wall or similar surface. However, in my experience it is far more effective (and I think easier) to simply get a close look directly at the sensor with the help of a loupe with a built-in illumination source.
I have been using the Carson SensorMag™, and have found it to be very helpful in evaluating whether the sensor on my camera needs cleaning. I use the SensorMag to check the condition of the sensor before cleaning, and again after cleaning to make sure I’ve done a thorough job.
The SensorMag provides a 4.5X magnification, along with strong LED illumination built-in. This loupe can be set on the lens mount of the camera body when the camera is set to manual sensor cleaning mode. In addition, the loupe can swivel out of the way so you can still make use of the LED illumination while cleaning the sensor.
You can find the Carson SensorMag here to get more information:
And of course there are also a variety of other similar products from other manufacturers that provide the same features. The key is to make sure you have a loupe with good magnification and with a built-in LED illumination source.
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