Achromatic doublet lenses consist of two optical components cemented together to form an achromatic doublet which is optimized to correct for on-axis spherical and chromatic aberrations. Achromatic doublet lenses are far superior to simple lenses for multi-color ("white light") imaging. The two elements composing an achromatic doublet lens (literally, "a lens with no color") are paired together for their ability to correct the color separation inherent in glass. Negative achromatic lenses have a negative focal length and are used for image reduction or to spread light. They are most often used as Barlow lenses to extend focal lengths.
Experimental Quality Negative Achromatic Lenses are offered in several experimental grade options. Grade 1 is standard optical glass, edged, free of visible scratches, chips, stains, or oxidation. Grade 2 is unedged, non-optical glass, small chips, slight stains, or other defects. They may have slight edge cement separation.
Note: Specifications for experimental grade optics may vary as much as 10% from those listed. Also, no additional information is available other than what is provided.