[Rollei] H1 filter for Tessar and Xenar only, why?

[Carlos Manuel Freaza <cmfreaza]

I have found a Rollei catalogue dated 1961 promoting
the Rolleiflex cameras and accesories for color
photography.The following notice about the H1 in the
page on the ROLLEI FILTERS is strange for me:
"H1 (Not necessary for use with the 5-element Planar
Xenotar and Sonnar) UV filter, especially designed for
long distance colour photography...."etcetera. In
other words, the filter is necessary for color
photography for the Xenar, Tessar and Triotar only,
not for the Xenotar and Planar, why?. The Tessar and
Xenar have excellent color performance  using the
modern color film, maybe the problem existed using the
old color films with the Tessar and Xenar. I remember
again the sixth element added for the Planar and
Xenotar 3.5, maybe some problem with respect to these
old color films.-

All the best
Carlos

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