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Originally Posted by mickoking
Looks nice and I bet it is but can you call a doublet a true apochromat?  |
The APO tag is an expression of a scopes performance, not how many lens it has. The Takahash FS series were all doublets and had absolutely no colour. The rear lens was ED glass like the ED80 but the front lens was pure flourite crystal, not crown glass. The performance of the Tak is in another league altogether. I say "was" because they are not made anymore. Japanese manufacturers are not allowed to make flourite lenses anymore because of environmental reasons. The FS series has been replaced with the TOA which is a traditional triplet arrangement.
Manufacturers in Taiwan (like Willian Optics) are still allowed to make flourite lenses. William are the OEM for the Express80.