Thursday 13 December 2012 by Tim Zoltie

The term 'conversational distance' is often used in personal injury and clinical negligence claims to describe the measurability of the prominance of a scar or deformity. It is deemed suitable for this purpose, yet in medico-legal photography it has no meaning.

It is clear that 'conversational distance' is not a descriptive measurement, so why is the term used so often? The term provides a suitable description of an injury in its context. A claimant's physical scarring may play a large role in the assessment of quantum, and a medico-legal report or a solicitor's notes must provide details on how it appears. For example: 'The claimant has a two-inch scar prominent at conversational distance on the left lateral of his right thigh.'

While conversational distance is worked out at an average distance of one metre, the need for accuracy is minimal. The statement is only aimed at pointing out the scar can be seen from a short distance away and as such is suitable for this purpose. As clinical photography is strictly about accuracy and measurements however, this term as currently applied in claims is too broad to provide any sense of standardisation, and this distance can not be identified or repeated. When an instruction states: 'Please photograph the left lateral of our claimant's right thigh from conversational distance,' the question becomes is this the distance from which to photograph the subject? Or is it how much of the claimant's body is in shot?

The key element of clinical photography is standardisation. It is key to providing the accurate portrayal of an any lesion or injury, using standard operating procedures to ensure all photographs are correctly scaled, colour balanced, and can be held in comparison to one another. A standard operating procedure in the case of clinical photography is developed through local and field specific protocols, involving specific distance measurements, flash and camera settings.

When photographing a lesion, a clinical photographer will photograph a 'locator' and a 'close-up'. While a close-up is defined by the size and scale of the lesion, the locator is defined at a set subject distance. The principle behind a locator is to identify the location of the lesion and view it in context to the rest of the body, thus having a similar purpose in principle to 'conversational distance'. The difference between them however, 'conversational distance', has no defining measurements, while in clinical photography a 'locator' has a set scaled subject distance which is measured by the use of a SLR's fixed focal length lens.

Subject distance, lens choice and camera settings all play a major part in photographic reproduction and can have a large effect on how an injury is portrayed. Subject distance in this case can be altered by simply including more of the body in frame, thus reducing the size and impact of the scar. For example, a scar on a wrist photographed at 'conversational distance' would look very different if the full arm was in shot, or just the hand and wrist. The distance therefore would need to be clarified. Alternatively taking the photograph at conversational distance would vary greatly depending on what lens was used. The brief is therefore decided by the photographer who is effectively deciding on how much of the body to include in the frame.

In clinical photography this is worked out by set protocols and standard operating procedures which are broadly defined by a locator and a close-up. The locator being pre-defined areas of the body which are shot dependent on which area the lesion is located. While these protocols may vary slightly between clinical photography departments, the overall result is the same: a standardised repeatable result is achieved. If all medico-legal photography were shot in this manner, standardisation could be more easily achieved.

A different perspective

So, the photography of a claimant's injuries for a personal injury or clinical negligence claim can vary greatly depending on the settings used to produce the final image. As each variable can substantially alter the final photograph, there is a high possibility that any photographic evidence submitted may be inaccurate or even misleading. Perspective distortion is one of these variables, and is also a prime example of how photographic images can be manipulated even before the images are captured in digital format.

The above two images were both shot on the same camera (Canon EOS 5D Mark II digital SLR), with the same lens (Canon 24-105mm f4 IS) at variable focal lengths. The left image was photographed at 35mm, and the right at 100mm. This is a prime example of perspective distortion. As you can imagine, in terms of expert witness evidence the difference between the two above images could be paramount. Say for example, the above image was taken to portray the physical features of the nose for a clinical negligence claim against a surgeon following a rhinoplasty operation.

The image on the left would suggest an extenuation of the nose and in context, appears substantially large in relation to the face. This is therefore quite misleading. To avoid this distortion, the photographer must increase the subject-to-camera distance, providing a more accurate result and avoiding distortion. This would then display the nose in its true context at the correct focal length.

Tim Zoltie is clinical photographer at Leeds Teaching Hospitals and proprietor of Clinical Photography UK