The Digital Photo Guy

“Dry” vs “Wet” Sensor Cleaning

by on Jun.24, 2011, under gear, Monday Morning Tips

Why the “Dry” Method is Superior to the “Wet” Method

The “wet” method was developed during the early days of dSLR and involves methanol. It was, and still is, highly effective but some ugly side issues have surfaced along the way.

The image to the left is the sensor assembly from a Canon XTi. Notice the sensor is actually behind two low-pass filters. The first filter incorporates the self-cleaning mechanism. A piezoelectric element at the top vibrates low-pass filter-1 to shake off dust. This is what you are actually cleaning. If vibrating the glass filter can shake off dust, it stands to reason that mopping it with a toxic chemical is probably overkill. A good broom will do the trick and that’s the “dry” method.

First, methanol is hygroscopic meaning it attracts and retains water from the air. It must be replaced regularly or the water can leave streaks. Being human, people will be reluctant to throw out a bottle of methanol that’s 90% full. It will look and smell the same and only chemical analysis will reveal the methanol is contaminated. Keep in mind that pure methanol evaporates immediately. Any water in it is left behind, creating a streak where the filter was swabbed.

The “dry” method has no such issues. It is a mechanical device that is used until visual inspection shows the tip is worn and needs replacement.

Second, there have been instances where coatings and adhesives used in the manufacture of sensor assemblies have been damaged by methanol. Owners of Canon 1Ds, 5D and 400D/XTi have all reported damaged sensors. A new fluid developed by Photographic Solutions was supposed to eliminate such damage but has now been discontinued. There are many conflicting opinions about methanol. Why take the chance?

The “dry” method has never been implicated in any damage to sensors. This method requires no flammable, toxic materials.

Third, methanol is highly flammable and banned by TSA (Transportation Security Administration.) This means you can’t take it with you when you fly. What is your backup plan if you discover a large blob in the middle of your sensor while on a two week safari in Africa? Not only is it flammable, it also degrades the plastic bottle it comes in. The bottle becomes brittle and, without warning, suddenly disintegrates in your hand. What if you are near a source of ignition when that happens? A damaged sensor may be the last of your worries.

Again, the “dry” method uses an innocuous mechanical device designed to clean delicate optical surfaces. It is designed for just one specific purpose. It is not a general purpose solvent like methanol. Did you know ancient Egyptians used methanol as a component of their embalming fluid?

Bottom line, the “dry” method is to the “wet” method like a shovel is to a stick of dynamite for digging post holes. A shovel is a simple, mechanical tool designed for the job while dynamite is an all-purpose, chemical tool designed demolish things.

The only real downside to using a LensPen is the number of fake knockoffs that can damage your sensor. That’s why I always recommend buying from Artie Morris at BirdsasArt.com. Artie has been using LensPens for many years and tht’s where I learned the “dry” method. (I have no financial interest ties with Artie Morris or his site.)

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2 Comments for this entry

  • Deena

    Based on your recent webinar for cleaning the sensor, I was able (after a couple of tries) to clean the “schmutz” off the sensor. I feel confident now in cleaning the sensor. Thank you Lee.

    • Lee

      Deena,
      Thanks for the feedback. Confidence is 99% of cleaning a sensor. The other 1% is having the right tools. I’m sure your sensor is happy as well! 😉

      Lee



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