Posted on 22 Comments

Polarized Light Photography for Art Documentation

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Polarized Light Photography eliminates surface reflections and it’s used by professional photographers for high quality documentation of art. The American Institute of Conservation guide to digital photography has in the chapter “Visible Light Photography” a short paragraph on “Polarized Illumination” [1]. This post adds my insights into this method.

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Light Polarization

A single particle of light can be imagined as a wave which propagates from its source into space. A beam of light from the sun, a halogen or an LED lamp, is composed of multiple light waves which vibrate in any directions.

Light from a bulb or an LED lamp is non-polarized. Light waves vibrate in any direction while propagating from the light source into space.

When we want to polarize this light source we put in front of it a polarizing filter which allows through just the light waves vibrating in one specific direction.

A Polarizing Filter allows through only the light waves vibrating in a specific direction.

A classical experiment with polarized light is that done with a calcite crystal and a polarizing filter.

 

Why Polarized light for Art Photography?

Our goal is to eliminate glare in our photos of paintings: in particular, those ugly reflections from varnished paintings. This is the trick: Light from the lamps can be Reflected or Diffused from a painting. Reflected light gives ugly glare while a diffused light is pleasant. When the light is reflected it keeps its polarization. When the light is diffused it loses any polarization. So, when we send a polarized light onto the painting, the glare is a polarized beam while diffused light vibrates in any direction.

Reflected light keeps its polarization while diffused light vibrate in any direction.

The final step is to add a polarizing filter on our camera and rotate it 90 degree so to extinguish all reflected light.

A polarizing Filter on the camera cuts off the reflected light, extinguishing  glare.

See it’s to believe

As usual, we want see some experiments. For this post I used a painting by Domenico Di Mauro, painter of colorful Sicilian traditional carts, currently 99 years young. He still works in his studio which happens to be beside my place. He’s one of the last practicing this craftsmanship.

This is the video:

 

Circular filter on camera at 0 degree (Up figure) and 90 degree (Down figure). The Polarized light photograph shows colors much more saturated and glare extinguished. See detail of coin (10 cents of Polish Zloty).

Equipment

Polarizing screens.  We used laminated polarizing sheets, width 17″ that we use for the Dowel DP 1000 W lamps.

Circular Polarizing filter for the camera. Don’t use a linear polarizing filter for the camera.

Linear Polarizing Filter VS Circular Polarizing Filter

If you do manual focus you can still use a linear polarizing filter. You need a circular polarizing filter when you work in auto focus. Indeed, the focusing system of the camera  gets hard time to focus when it receives polarized light. The circular polarizing filter resolves this problem. It is essentially a liner polarizing filter that diffuse the polarized light just before feeding it to the camera.

A video on linear polarizing filter and circular polarizing filter:

References

[1] The AIC guide to digital photography and conservation documentation – second edition, Jeffrey Warda editor, American Institute for Conservation, 2012.

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22 thoughts on “Polarized Light Photography for Art Documentation

  1. Hi,
    So, what is the best solution when having linear pol filters in front of flashes… with linear filter, or circular in front of lens ?

    1. Hi Dominique,
      The same logic is applied to flashes. They are the same as continuous lighting (such as halogen lamps) when it comes to polarizing filters. So, just set up your experiment as you would do with halogen lamp (linear polarizer on the lamp / flash) and circular polarizer on the camera.

  2. Thanks. My artist friend and I have been going nuts trying to get rid what he calls ‘sparkles’ in my photos of his artwork.

    1. great!, glad it helped!

  3. I think the diagram / explanation is a little misleading. Is it not the case that the diffused unpolarised light consists of lots of beams each of which originated at the source but which have bounced around the room (with a load of different paths for different beams), losing polarisation in the process, before eventually striking and reflecting off the painting at an angle that sends it into the camera lens? You make it look like the “diffuse beam” somehow goes directly from source to painting to camera.

  4. Good article. However, it may be a little misleading. Presumably the diffused light consists of multiple beams that have bounced around the room (taking all kings of paths) losing their polarisation in the process before striking and reflecting off the painting at an angle such that they finally travel into the camera lens. You’ve made it look like the diffuse light somehow goes straight from source to painting to lens.

    1. hi Ben, thanks for u comments. Sure, that is a diagram of a perfect world experiment. you should avoid as much as possible diffused light from the surrounding walls.though, the exp works pretty fine even in not 100% perfect condition.

  5. Hi. Can I clarify about your light set up? Are you using juts one light source, or two? I am shooting some art work in the new year and want them to be spot on. I was going to use two studio flashes with softboxes located in 45° angles. However now I have came across your great article that has opened up a lot of ideas for me, so thank you!

    1. Hi Anna, my first suggestion is to experimenting. This is the way you can master anything, hands-on! so you can figure out your own specific set-up, also based on what you have and your specific needs. you can use one, two, 3..more lamps, they just need to be polarized with the same polarization direction, which means to have the filter in the same orientation. Test,test, test and you will figure out 🙂

  6. What about the saturation added to the immage? I tried to shot with a color checker, but the calibration of the camera in post production didn’t work as it should and the saturation remains. The camera exposure values used to correctly espose the image gave the black patch near to the absolute black, and also the white one to the absolute white. So I tried to correct the rgb values of the gray patches manually, but the result was bad.
    How do you solve this problem to respect the chromatic correspondence of the artwork ?
    Thanks for your articles!

    1. hi, thanks for the question. When you do PL photography, you are viewing the object with different light and also your color standards. The painting looks more saturated because you are removing the relfected light which is a natural property of the painting. So, bottom line you are not expected to get the same image as you look at it with naked eye, because in PL photography you are looking at the painting with light that is now polarized and interact differently with the object.

  7. Will this also work for 3-dimensional art work such as sculptures?

    1. yes, it will.

  8. I use a prophoto pack with two lamps. Each is fronted with a diffuser then a sheet of polariser. remember you lose up to four stops of light by passing the light through the polariser on the camera and the lamps themselves. As for the reflected light from ceilings and suchlike, I sometimes use a large black voile material draped over light stands. Though this is only really needed for dark high varnish paintings.

    Purists don’t like using polarisers, because you can’t achieve a good Delta ae result…. https://deltae.picturae.com I use them most of the time with thousands of paintings photographed.

  9. For paintings with texture, doesn’t the polarized light flatten them out? You lose the apparent 3D qualities of the impasto and the image looks flat. Is there a way to fix that?
    Thanks for the great information!

    Ken

    1. Hi Ken, you can change the lamps angle to make them more raking, so to increase as you need the surface details

  10. Hello from Bucharest, Romania!

    I lately found out about the linear pollarization solution from someone who uses really valuable gear also to reproduce artworks. The photographer particularly had problems with my works – very textured oil painting, satin varnished (but eve so, troublesome).

    I do photo reproductions also, myself. I don’t own top gear, neither have I everything I need, but I am on my way, in developpment. However, until now, I’ve photographed and post produced hundreds of art works and exhibition photos, mainly from passion and for my personal archive, until now.

    Would you please tell me which polarising filter might best apply for photographing art works, and especially painting and drawing (drawing framed under glass also). I saw that there are several types, like HN32, HN38, HN42. Here is the website where I found the info:
    https://www.knightoptical.com/stock/default/catalog/product/view/id/2097/s/hn32-equivalent-sheet-polariser-914x558mmx0-38mmthk/
    Or maybe there are also other better types… I don’t know.

    If I understood well, the combination also works for video, the only thing is to fave the circular poll. filter on the video cam, right?

    Thanks a lot, already, for this initiative to share this knolledge and experience!

    Looking forward,

    Constantin

    1. Hi Costantin, nice to hear from you. My suggestion is to start with cheap filters that you can find easily. Practise and once you master the method you can see if you need more expansive tools, or you are already satisfied with the results.

      1. Thank you for the reply.

        I would choose cheaper filters, but actually I am not sure what to choose, as there are different types, with different features, allowing the light pass through in different ways. Some just allow one frequency, some allow also other frequencies. And I don’t understand how these features of each filter would concretely influence the light I use, in order to get best results for art work reproduction.

        I would be most grateful if you could give me a hint, or recommend me an article, or some documentation on how to use the filters for this kind of photography, that I can access in order to get an idea – but some sumarized information, that I could understand as a non-profesional în optic physics.

        Thank you!

        1. the only way is to practice, practice, practice!!!!! That post has all you need, just read it carefully!

  11. Hello!
    I just found this post and found it very informative. I do have a question.
    Can this work on an LED light panel?
    (It has 100 individual leds.)
    I have CPF but not the sheets.
    Thanks!

    1. sure,it will work also on leds

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