Originally Posted by
ridax
Funny enough, those are most probably the early (and new and exotic those days) specimens of MODERN yellow glass filters. The filter I described above was much older, coming from the pre-Protar "Zeiss Anastigmat" era. As your 1931 catalog states, the modern sharp-cut filters are superior in their smaller filter factors for the same degree of spectral correction. The difference in the filter factors / exposure compensation needed is still negligible for panchromatic films but is pretty noticeable for orthochromatic emulsions widely used a century ago.
But the modern red, orange, yellow and the majority of UV-absorbing glasses introduce additional flare into the optical system, while the old amberish Zeiss filter, as well as the modern Wrattens, Tiffens and the yellow-green glass filters do not.
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