Cross-Polarised Photography
Definition
A photographic technique using polarising filters on both the light source and the camera lens to eliminate surface glare and reveal subsurface bruising, particularly useful in patients with darker skin tones.
- Equipment
- Polarising filter on the light source and on the camera lens
- Filter orientation
- Source and lens filters set at 90 degrees to each other
- Effect removed
- Surface glare and specular reflection
- Clinical use
- Revealing subsurface bruising, especially on darker skin
Common questions
How is this different from ordinary flash photography of an injury?+
A standard flash bounces light straight off the skin surface, producing glare that can hide colour variation underneath. Crossing the polarisers blocks that reflected light while letting light that has scattered under the skin through, so subsurface bruising becomes more visible in the image.
Does cross-polarised photography replace standard clinical photography of an injury?+
No, it supplements it. Standard photographs document the visible appearance and scale, while the cross-polarised image is taken alongside to show detail that surface glare or skin pigmentation would otherwise obscure.
Related terms
- Bilirubin
- A yellow-orange breakdown product of biliverdin, seen as the yellow-brown phase of a resolving bruise. Its appearance indicates advancing haemoglobin degradation.
- Biliverdin
- A green breakdown product of haemoglobin, appearing as the blue-green phase of bruise colour change. Biliverdin is then converted to bilirubin.
- Haemoglobin
- The iron-containing oxygen-transport protein in red blood cells, composed of four polypeptide subunits each with a haem prosthetic group. Its pseudoperoxidase activity...
- Oxyhaemoglobin
- The form of haemoglobin in freshly shed arterial blood, where iron in the haem group is in the ferrous (Fe²⁺) state and...
- Tissue Laxity
- The looseness of subcutaneous tissue. High laxity (eyelids, scrotum, elderly skin) allows blood to spread widely from a relatively small vessel injury,...