My earliest attempts at coin photography were made more than fifty years ago when I purchased a Pentax Spotmatic single lens reflex camera. It was clear from the start that a tripod would be essential for many of the reasons given in the 'Set-Up' section of this article, but lighting was an altogether more complex and challenging aspect. In order to assess the effects of many variable factors, it was necessary to take (and log the details of) multiple shots, but the limit of standard 35mm film was 36 exposures, after which a wait of several days was required for processing. Most of the experimentation was carried out using daylight as the source of illumination, as it quickly became apparent that household tungsten-filament bulbs did not produce satisfactory results. The findings, still relevant today, are summarised below.
Neither dull weather conditions nor bright sunlight produce satisfactory results. The former results in dull, flat images, and the latter in unacceptably contrasty images with ugly dark shadows cast on the background. The best results are achieved when the sun is lower in the sky, diffused by light cloud cover, but still clearly visible. Unfortunately, the nature of these conditions is such that the level of light is constantly changing, so producing two identically exposed images (obverse and reverse) depends on luck and how quickly you can complete the exercise.
Fortunately, the ideal conditions described above can now, to a large extent, be replicated artificially at very little cost. For just a few pounds a multi-LED lamp of the type shown on the accompanying illustration can be obtained. The lamp has a colour temperature approximating the value of the daylight described above (c.5500K), and opaque filters can be fitted to diffuse the light. It has advantages over sunlight in that the intensity is constant and the direction and angle of illumination can be adjusted by moving the lamp rather than reconfiguring the set-up.
Generally, I have found that illuminating the coin from an angle of about 45 degrees above its horizontal plane, and at a distance of about 400mm, produces a good result. The coin should normally be orientated such that the top of the design ('12 o'clock') faces towards the lamp's position. Slight variations to this 12 o'clock guideline are appropriate in a few cases. For coins that have a left- or right-facing bust, for example, it is often desirable to rotate them slightly such that the light falls on the ruler's face rather than on the top of the head. Similarly, the appearance of transverse scratches can be mitigated by ensuring that they are not highlighted by perpendicular illumination. Notwithstanding these exceptions, I would advise that 10 o'clock and 2 o'clock are the limits that should normally be observed, as beyond them the lighting looks increasingly unnatural.
In the Set-Up section I briefly mentioned the use of a clear glass platform to support the coin. The purpose of the glass is to eliminate the external shadow that would otherwise occur around its lower half. Instead, a 'drop-shadow' of the full coin is created on the background below. As the drop-shadow is displaced from the coin, it can be eliminated from the image altogether, or easily cropped during post-processing. Removal of external shadows greatly facilitates post-processing of images, and is often desirable in its own right for illustration purposes. Where required, external shadows can be reinstated artificially at the post-processing stage.