Card dating post
And of course any image that contain a regularly patterned series of dots is not a photograph at all but a ink printed image.Some halftone cards were printed on high gloss paper to resemble a photograph but their screen patterns will give them away if one is vigilant.Observing this shiny crust, no mater what the color, is a quick and sure way of telling if you are looking at a real photo.
A studio sometimes grew to the point where additional photographers were hired but all the photographs produced were published with the original photographers name.
At other times a studio might buy out the negative inventory of older photographers and reprinted their images under the current studio name.
Most old photo papers used silver in their emulsions.
As time passes this silver tends to migrate to the surface of the print creating tell-tale metallic patches.
Collotypes, which provide the finest detail of all printing methods are sometimes confused with real photo postcards.
But even collotypes will exhibit a discernible grain when magnified.The photosensitive solution used in this process soaks into the paper, so the original paper surface remains dominant in the final print.This gives these images a very matte look not normally associated with photography, and making some easy to confuse with collotypes.Light energy alone, usually from the sun, reacted with the light sensitive chemicals on the paper’s surface to produce an image.They only needed to be fixed to preserve the exposed image.- This process was invented in 1842, but its first known use for a postcard was in 1888.