Not so black and white

Museums of History NSW recently acquired a polarising lens, which has been used to digitise black and white photographs from the Rouse Hill Estate Collection. Taking advantage of the heritage conservation works at Rouse Hill Estate, Collections Care removed numerous photographs from inside the house and sent them offsite so they could be worked on by the Digital Assets team.

Black and white photographs can deteriorate and undergo chemical changes over time. One common issue they face is the development of ‘silver mirroring’ or ‘silvering’. This is a form of degradation where metallic silver on the surface reflects light, creating a glare or shine that obscures image details.

The most effective technique to eliminate the appearance of silvering on black and white photographs is ‘cross-polarisation’. This process involves polarising both the light source and the camera lens to cancel out reflective light and reveal the underlying image details that are otherwise lost with standard copy lighting techniques. The Rouse Hill Estate Photographic Collection Digitisation initiative has created more than 1,500 digital assets over the past six months, although these won’t be available on the online catalogue for some time.

Belinda Christie from the Digital Assets team demonstrated how the polarising lens is used in her photo shoots of these collection items. In the gallery below, you can see Belinda’s working space as she sets up for and carries out the cross-polarisation process. The technique first requires polarising both light sources using special filters. A cross-polarisation filter is then applied to the camera before the photo is taken. You can also compare an image digitised without the polarising filter and lens to the same image digitised with this process.