1 Introduction to Medical Photography
This chapter introduces the discipline of medical photography, a specialized genre requiring meticulous control of camera settings and environment to obtain optimum quality images which accurately depict the human body. Fundamental principles of photography including exposure, ISO, aperture, shutter speed, focus, focal length, and composition are discussed. Understanding these is a prerequisite to creating high-quality medical images.
aperture, composition, depth of field, exposure, focal length, focus, introduction, ISO, medical photography, shutter speed
Almost everyone in the current era is a photographer to some degree, or at least takes several pictures. Yet very few people, even serious photographers, have any formal training in the specific demands of medical photography. As a result, the quality of medical images is highly variable and often substandard. With proper implementation of the principles and techniques described in this book, the reader will be equipped to create outstanding medical images to accurately document the human face and neck in almost any conceivable clinical situation.
Medical photographs are significantly different from snapshots or even artistic portraits (Fig. 1.1). They are taken using standardized views under tightly controlled conditions to accurately display the real state of the patient at that point in time. Unlike artistic photographs, the goal of medical photographs is not beauty, or to show the patient’s best features while hiding their flaws, but to serve as a medical record. For many diseases or clinical situations such as cosmetic surgery, photography has long been recognized as mandatory, but this is far from universal. However, within the head and neck, there is far more need for photography than with other regions of the body, and the ability to create quality images is increasingly important in today’s practice environment. A good photograph can be the difference between a paid and an unpaid insurance claim, a settled and a dismissed malpractice suit, or most importantly, a happy and an unhappy patient.
It is beneficial for all physicians who use medical photographs to also learn how to take them. Many physicians are fortunate enough to work with dedicated medical photographers, majority of who are excellent, but even an outstanding photographer may not know the specific needs of the referring physician or the clinical situation in question. Even a superficial understanding of the photographic principles in this book will allow the physician to communicate with the photographer to achieve optimum results. For medical photographers, this book can be used not only as a reference standard but also as a help to communicate with referring physicians to produce the best quality product.
Fig. 1.1 Comparison of (a) a snapshot, (b) artistic portrait (c) medical photograph
The human face is one of the most commonly photographed subjects, yet it is remarkably difficult to portray it accurately. This book will address each of the difficulties in this process in a stepwise manner, beginning with the basics of photography, then progressing to more advanced topics specific to photography of the head and neck, before ending with an atlas of standardized photographs. With careful study, the right equipment, and a modicum of practice, the reader should have no problem in reliably producing the images found in this volume.
To create great images, the entire photographic process must be controlled carefully, beginning with acquisition of the image under ideal conditions. Modern cameras allow the user a very large degree of control over several settings which must be optimized. While every camera is different in terms of the exact controls and specifications, there are certain standardized functions which must be understood. The most critical of these are ISO, shutter speed, and lens aperture. The interaction between these three is often referred to as the “exposure triangle.” Other critical basics to understand are depth of field, focal length, focusing modes, the fundamentals of image composition, and standard hand-holding techniques.
Exposure is the most critical element of photography. Artistic photographers use exposure techniques to create elements in their images such as blurred backgrounds, sharply frozen action, or blurred motion. Medical photographers must show their subjects in clear, consistent detail, and their exposure choices should reflect that aim.
Digital sensors are limited to certain amounts of light at which they will show details; too much light, and the resulting image will show large white regions with no detail at all; too little, and the resulting image will show large black regions similarly lacking detail. A correct exposure renders highlights, shadows, and midtones with proper detail (Fig. 1.2). Exposure can be assessed subjectively by looking at the image and determining if it looks too dark or too bright, or quantitatively by using the histogram feature. A full discussion of histograms is beyond the scope of this book, but in short it allows a graphical display of the tones present in an image. Underexposure creates a left-biased histogram, and overexposure creates a right-biased histogram. Extremes of either type result in “clipping,” where detail is lost in the highlights or shadows. For medical purposes, the ideal histogram is roughly a bell-shaped curve biased slightly to the right of center, with a large midtone peak that correlates with the uniform background. Exposure is controlled by adjusting ISO, shutter speed, and aperture, which also affect the appearance of the image in ways discussed later.