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Photographic grey, also known as works grey, was a paint scheme commonly applied to steam locomotives during the period before colour photography became commonplace. It was applied to allow sharper, more detailed images of the locomotive to be recorded. The first photographs of railways and their locomotives were made by private individuals, but by the 1860s the railway companies themselves were keen to create official photographs of the highest quality possible of their latest designs, which led to the adoption of photographic grey in railway photography. ==Usage== Railway companies wished to record their latest locomotives for use in publicity material and advertisements, and as a technical record of their work. This was especially the case in the United Kingdom, where all but the smallest of the 'pre-grouping' companies owned their own locomotive works and designed and built their own locomotives. For the numerous private locomotive builders it was especially important to have high-quality photographs of their latest builds to showcase to potential customers. Most companies used dark green or red liveries, with virtually all goods locomotives painted all-over black to reduce the need for regular and extensive cleaning. These dark colours provided poor levels of detail with the glass-plate camera technology of the time, especially when the camera was placed at a suitable distance to cover the entire locomotive in one shot. Early film emulsions were orthochromatic, insensitive to red light, and so the many red or reddish liveries would appear an indistinct black. The solution was to paint the entire locomotive a mid-grey (usually approximate to the modern shade of slate grey). This light colour reproduced well on the photographic plates and picked out the shadows and shading produced by the various components (such as the valve gear and wheel spokes) allowing them to be recorded in detail. Often a variant of the company's standard livery (such as the lining or company name and crest) would be applied in a darker shade of grey to complete the picture's use for publicity. To add to the detail recorded, once the negative had been processed the background behind the locomotive would often be inked out to provide a crisp view of the outline and shape. 'Works grey' also served the function of being a primary 'undercoat' of paint, allowing the locomotive to be used for test runs and checks to find any faults or required modifications before undergoing the expensive and often time-consuming process of being painted in a full livery. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Photographic grey」の詳細全文を読む スポンサード リンク
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