Spectral transmission graphs
I’ve updated the Spectral Transmission Graphs page with 7 new filters, courtesy of Coastal Optics (I sent them seven of my own personal filters for testing). See also the main review page of the Coastal 60/4 UV-VIS-IR APO macro.
The new spectral transmission charts confirm a nagging annoyance that several years ago caused me to give up Hoya HMC Super UV filters—they attenuate the blue end of the spectrum all the way to 500nm, yielding a non-neutral color balance. These days, my lenses nearly always image the world free of filters, but in dusty or salt-spray environs I do use a UV filter, always a B+W MRC.
Compare the Hoya transmission to the B+W UV 010 MRC; the Hoya rounds off the dark blue end of the spectrum. While this might be an advantage at high altitudes, a completely neutral filter is a better choice for most purposes—who wants neutered blues for sky, water, eyes, etc? Color rendition is frequently ignored when assessing optical quality, but it is one good reason the Zeiss ZF Lenses are so stunning by comparison to most lenses.
B+W UV 010 — almost perfect transmission in the visible band
Hoya HMC Super UV (0) — blue light is attenuated
By the way, did you ever wonder if “neutral density” filters are actually neutral? When I was researching The Sharpest Image I used a neutral density filter with the Nikon 200mm f/2. I observed that it imparted an odd color cast, which should be clear from the spectral transmission graph, this one for a B+W 3-stop filter:
B+W 103 ND 0.9 3-stop neutral density filter
