The Life-changing Magic of Cross-polarization

Excuse the clickbait headline, but I make no apologies because I’m not even exaggerating. My recent introduction to the technique of cross-polarization for photographing artwork has turned a challenging and frustrating task into something I now look forward to, because the process really IS like magic. Read on if you’re interested in learning how to remove ALL glare from your photographs of your artwork, even very dark paintings with a coat of gloss varnish.

The Struggle

Taking photos of my paintings is something I had never found a consistently reliable method for. The main challenge is always lighting the painting in a way that provides enough light to get a good exposure, while also minimizing the glare that results from light bouncing off the shiny surface of the paint strokes. The darker the painting, the more challenging this becomes, as the glare is much more obvious.

I had adopted various techniques over the years to help make it easier, such as lighting the painting from a single overhead source at a 35º angle, and hanging a black sheet behind the camera to prevent light from reflecting off the walls/ceiling. Another strategy I’ve seen is taking the photo outdoors in the shade of a building, but I never got consistent results with that method. Even with these kinds of ‘tricks’ it is sometimes impossible to completely eliminate glare, and some degree of touch-up is often required afterwards in Photoshop.

The Turning Point

This all changed when I finally bought a book that I’d had on my wishlist for years: Alla Prima II Companion by Katie Swatland, in which Katie explains the tools, techniques and materials of master artist Richard Schmid, who sadly passed away earlier this year.

The book is worth its weight in gold for a variety of reasons, but it was the chapter on photographing your artwork that introduced me to a technique I had never heard of before – cross-polarization. I’m no scientist, but in a nutshell, the process uses polarizating filters, which affect the direction of the light beams entering your camera sensor. You need lights with polarizing filters oriented in one direction (either horizontally or vertically), and then you also need a polarizing filter on your camera lens, with the opposite orientation to the filters on the lights. This combination filters the light beams in such a way that glare is completely eliminated. To make myself clear, this doesn’t just reduce glare, or help to make it less obvious, it removes all glare, even from the darkest, shiniest paintings.

The Equipment

After absorbing the information in the book, and doing a bit of extra research online, I had some shopping to do. I already had a pretty good camera (the Sony RX100 III), but it’s not a DSLR, so it doesn’t have a way to attach a filter to the lens. I contemplated a DSLR purchase, but eventually went with an adapter that holds any filter and attaches magnetically to my existing camera. Aside from that, all I needed was a polarizing filter to go on the camera, a pair of lights with diffusers and some polarization film to go in front of the lights. Here’s my shopping/price list (including shipping costs):

Total: £161

* It’s important to get a linear polarizing filter, not a circular one, or it won’t work properly. Circular polarizing filters are much more common, as unlike the linear ones they don’t interfere with auto-focus, so make sure you check before buying.

The Setup

Without going into too much detail, the setup involves positioning the lights level with the vertical center of your painting, at a 45° angle on each side, and just far enough back to get even light coverage with no hotspots or light fall-off. The polarizing film needs to be placed in front of each light, with each sheet in the same orientation, and making sure that they completely cover the lights. I’ll probably make some kind of holder for the film at some point, but for now a piece of tape attached to the top of the lamps is working fine.

Note that there shouldn’t be any other light source when you’re taking the photo, so it’s best to do this after dark, or in a blacked out room.

The camera is positioned directly in front of the painting on a tripod. I measure the distance from the centre of the painting to the floor, and then make sure the centre of the camera lens is at the same height, to help get the painting framed as squarely as possible (although it’s very easy to straighten things up later in Lightroom if it’s not perfectly aligned). With the main room lights still switched on, I set the camera focus manually (since the filter messes with auto-focus), then switch the room lights off, leaving only the polarized lights switched on, and I’m ready to take the photo. I won’t go into camera settings here, maybe in another post.

The Magic

If you look at your camera screen when the polarizing filter is in the same orientation as the polarization film on the lights (e.g. all vertical), you’ll likely see a lot of glare from the lights. But if you just turn the filter 90º so it’s horizontal (there’s a little line on the filter to indicate the orientation), you will see all that glare magically vanish before your eyes, leaving only the true colours of every brushstroke on your painting.

Here’s a quick clip of me turning the filter on the camera so you can see the magic in action:

And here’s how the image looks, with and without cross-polarization:

Amazing, isn’t it?

Here’s another example, showing a photo of a skull study I took before I learnt about this, using the techniques mentioned previously to minimize glare, and the same painting photographed with cross-polarization.

What do you think? Is this something you’d like to try with your own artwork? Or if you’ve already tried it, do you have any other tips I haven’t mentioned here?

Leave a comment if you have any questions and I’ll be happy to answer them if I can.

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