Many historic buildings and tourist sites have signboards explaining their history. Some such signboards and stone monuments have photos on metal placed on them. Some commercial signboards also have similar photos on metal, and these are a type of metal plate. In recent years, services for processing photos on metal plates have become available to individual customers. Many of these products use pigments to show dark parts of a photograph.

In certain cases, such special photographic emulsions are used. Pigments left outdoors wear out in several years, and can last up to less than 20 years. Photographic emulsions have specifications to last up to 20 years. It is easy to find stainless steel signboards outdoors with worn out black parts, leaving only shallow engraved marks.

Millennium Photo does not use pigments or plating to express colors; therefore, colors never wear out or peel off.

Moreover, in the same way as the below-mentioned three methods (photo impact printing, daguerreotype, and metal plate printing), images processed using these methods cannot be seen well depending on the angle. In general, this type of metal product uses coarse dots in creating images, in the same way as with laser engraving. These are similar to photos seen in newspapers, and these have totally different visual characteristics than those with Millennium Photos, which employ photographic engraving technology to express a three-dimensional feel by reproducing photos using lines. Please see here to read about engraving method.