The ready availability of image-processing software makes possible adjustments to and enhancements of images after the photographic stage. At its simplest, post-processing allows images to be ‘touched up’, cropped to size, rotated to correct minor errors in orientation and stitched to show obverse and reverse together as a single picture. All of the above have been employed on the images that accompany this article. This section explores the slightly more advanced aspects of post processing, namely applying a separate background image and restoring external shadows. The use of a plain white background and the elimination of external shadows at the photographic stage, as covered elsewhere in this article, greatly facilitates this process.
The first images shown here are the two sides of a coin photographed in the way described in the 'Set-Up' and 'Lighting' sections of this article. Because the background is clean, plain and uniform, and the coin is free of external shadows, the 'magic-wand' tool of any image-processing package can be used to select it in its entirety. The selection can then be inverted such that it is the coin image, rather than the background, that is selected. At this point, the selection can be converted to an 'object'.
The third image is that of the textured background on which the coin will be placed, in this case a blue linen book cover. This has been photographed in much the same way as the coin, except that it was supported on the lower wooden platfom of the illustrated set-up, rather than on the clear glass platform. The most important considerations in this case are that the background image is larger than the two coin 'objects', and the lighting is from the same direction.
The fourth image shows the obverse and reverse coin 'objects' moved on to the background image, centred vertically and equally spaced horizontally. It will be seen that the coin now appears to be floating above the background, rather than resting on it. This is rectified by using the image-processing package to add shadows to the two coin objects. The shadows should be applied where they would originally have occurred, which in the present case is at the bottom of the coin. The size, transparency and softness of the shadows should be adjusted such that they are plausibly consistent with the thickness of the coin and the nature of the lighting used at the photographic stage.
The fifth image shows the final result after merging the objects and the background.