(e.g. from an artificial lamp) will decrease in brightness over a shorter distance than light falling on an object further away from its source (e.g. from a north facing window). This is known as falloff, and means that any artificial lighting used must be fairly powerful and positioned a long distance away from the subject in order to accurately imitate north light. In Photography Photographers use north light for similar reasons as painters but have access to electric lights as well. The use of softboxes and bouncing speedlights against umbrella-shaped diffusers strives to recreate the soft shadows that north light produces. These processes are popular in portrait photography. The Dutch Golden Age of painting has also left a legacy – since the early 20th century, photographers and filmmakers have used Rembrandt lighting to return some dramatic effect to diffused light, both in portraits and cinema. This entails a key light illuminating the subject (such as a north-facing window) and a reflector facing the other side of the subject. While this lighting was not formally named in Rembrandt's time, it appears in some of his paintings. Like painters, photographers can modify south light or use artificial lighting as a replacement for north light if needed. However, they can also employ post production software such as Adobe Lightroom and Photoshop to correct exposure and temperature. In addition, dedicated software such as Robin Myers Imaging EquaLight can adjust for lens and lighting falloff, which is especially useful for fine art photographers. Effect of Art Appreciation Before artificial lighting, both the artist and their audience would both see art under natural light (either coming from the north or scattered in some way to reduce glare). However, since the 1980s museums and galleries have become reliant on some degree of electric lighting. This means that the audience may see art differently to how it was intended and may also miss out on observing subtle changes in shadows and highlights as light moves throughout the day. Studies into art perception have found that the colour correlated temperature (CCT) of north light (~6000K) may be too cool for optimum appreciation of most art. For example, a 2004 study found 3600K to be the preferred temperature – a warm CCT which is commonly used in museums. A 2008 study by the Optical Society of America used different methodology to suggest 5100K as the optimal temperature – although this