Editing Autochrome Lumière (section)

== Viewing techniques ==
{{More citations needed section|date=February 2021}}
[[File:-Still Life of Flowers in a Stein- MET DP170766.jpg|thumb|''Still Life of Flowers in a Stein'', stereoscopic Autochrome photograph by the Lumières]]
[[File:Percy-MacKaye-Alwyn-Genthe-diascope.jpeg|thumb|Autochrome in an original diascope viewing case. [[Percy MacKaye]] photographed by [[Arnold Genthe]] ]]
Because the presence of the mosaic color screen made the finished Autochrome image very dark overall, bright light and special viewing arrangements were needed for satisfactory results.

[[Stereoscope|Stereoscopic]] Autochromes were especially popular, the combined color and depth proving to be a bewitching experience to early 20th-century eyes. Usually of a small size, they were most commonly viewed in a small hand-held box-type stereoscope. Larger, non-stereoscopic plates were most commonly displayed in a diascope, which was a folding case with the Autochrome image and a ground glass diffuser fitted into an opening on one side, and a mirror framed into the other side. The user would place the diascope near a window or other light source so that light passed through the diffuser and the Autochrome, and the resulting back-lit, dark-surrounded image would be viewed in the mirror. Slide projectors, then known as [[magic lantern]]s and [[stereopticon]]s, were a less common but especially effective display technique, more suitable for public exhibitions. Projection required an extremely bright and therefore hot light source (a [[arc lamp|carbon arc]] or a 500-watt [[incandescent light bulb|bulb]] were typical) and could visibly "fry" the plate if continued for more than two or three minutes, causing serious damage to the color.<ref>"Maximum Time Limit for Leaving Color Plates in the Stereopticon" (article subsection). ''American Annual of Photography, 1931'', '''45''':69</ref> Many surviving Autochromes suffer from such "tanning" and conventional projection is not a recommended means of displaying these irreplaceable images today.

However, a projector-like optical system (i.e., using condenser lenses for illumination, with a viewing lens in place of the projection lens), employing daylight (not direct sunlight) for the light source, can produce comparably excellent visual results—although for only one viewer at a time—without the hazards of actual projection.

The use of a "light box" or similar highly diffused artificial light source for viewing Autochromes, can damage the plates as the heavy scattering of light within and among the several layers of coatings on the plate degrades the color saturation. The slight pinkish tinge caused by colloidal scattering (the effect seen through a glass of water into which a couple of drops of milk have been mixed) is exacerbated, and the use of artificial light—especially fluorescent light—upsets the color rendition of a system which the Lumière Brothers carefully balanced for use with natural daylight.[[File:Mauretania in drydock 1928 autochrome process starboard side.jpg|thumb|[[RMS Mauretania (1906)|RMS ''Mauretania'']] photographed in 1928 using the Autochrome process.]]Making modern film or digital copies of Autochromes introduces other problems, because a color system based on red, green, and blue is used to copy an image that exists within the red-orange, green, and blue-violet system, providing further opportunities for color degradation. Vintage reproductions of Autochromes in old books and magazines have often been noticeably hand-adjusted by the photoengravers in an effort to compensate for some of the difficulties of reproduction, and as a result, they sometimes look more like hand-colored photographs than "natural color" ones. In short, it is very difficult to form an accurate impression of the appearance of any Autochrome image without seeing the original "in person" and correctly illuminated.

The lamination of the grains, varnish, and emulsion makes autochrome plates susceptible to deterioration with each layer being vulnerable to changes in environment such as moisture, oxidation, cracking, or flaking as well as physical damage from handling; solutions involve conservative lighting conditions, chemical-free materials, medium-range humidity control of between 63 and 68 degrees Fahrenheit in a well integrated preservation plan.<ref>Penichon, Sylvie. ''Twentieth-Century Colour Photographs.'' Los Angeles: The Getty Conservation Institute (2013), p 61, 78.</ref><ref>{{Cite web|url=https://rps.org/news/journal/2022/october/colour-mania-the-precious-world-of-the-autochrome/|title=Colour mania: the precious world of the autochrome|date=October 11, 2022|website=rps.org}}</ref>