Starting with the recent Philips Sonicare teardown investigation, I've reintroduced the use of my Canon EOS M100 camera to take pictures for project documentation. Its excellent sensor paired with a macro lens for close-up photography work quite well to capture small surface-mount components and related circuitry detail. Late in the investigation, I added polarizers to the setup and was amazed at how much of a difference it makes under the right circumstances.

My current understanding is: if I use a light source that is polarized in a direction, then take a photograph with a filter polarized in an orthogonal direction, most direct reflections are eliminated. This means the resulting pictures will not be blown out by reflective glare, even though the subject can be very brightly lit Letting us make out details we could not otherwise see.

Here's the Sonicare HX6530 circuit board again, taken without polarizers. All the solder pads are very shiny, as are some of the circuit board surfaces. I tell the camera to focus on the markings on the surface of the PIC16F726 microcontroller, but we can barely make it out.

And now a picture taken with polarization. All the shiny reflections are gone, letting us see far more detail that were previously obscured. PIC16F726's markings are now clearly legible.

This is a great tool to add to the project documentation photography toolbox, but like all tools there are right and wrong times to use them. Even though I can see details with the polarizer in place, some of those details may be misleading. Example: actuator coil pads 1 and 2 show up as red in the polarized picture above. I don't know why but it tells me to view colors in polarized pictures with skepticism.

But sometimes polarizers are just magic. There's clear packing tape protecting this solder joint. Normally the tape would directly reflect light into the camera sensor, causing a bright glare on the surface making this solder joint impossible to photograph. But a polarizer can filter out that glare and let the camera focus on the solder joint almost as if the packing tape isn't there. The downside of removing bright reflection is that it also removes a lot of visual cues for dimensions. Look at the red wire: all visual cues it is cylindrical are gone leaving it looking like a flat red thing.

Polarizer filters are sold for camera lenses for use in this and other scenarios. The Canon EF-M macro lens takes 43mm filters so I started with the cheapest option on Amazon (*) to see how well it worked. The outer ring is assembled from two parts: one part threads onto the lens and stays put, the other part holding the filter rotates freely letting me adjust the polarization angle. These initial tests look promising so I'll use the cheap filter until I can articulate a reason to move upscale.

The camera lens polarizer is cheap to buy and easy to use, but getting these results also require a source of polarized light. I think the easy solution is to buy sheets of polarizer film (*) and put it over your existing light sources, but that's not what I did. I wanted to put some old stuff to work.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.