On 7/13/2017 4:51 PM, Mike Gordon via olympus wrote:
Appreciate the filtered and unfiltered opinions as well as the skillful Moose
roll-over. I am not overly concerned about perfect WB as shooting raw
Raw would be no help, if the camera (and lenses?) didn't provide UV filtering
but it may be more of an issue with film.
Yes, big trouble. The problem is that the blue layer responds to both visible blue and to UV. It's then impossible to
remove the spurious UV exposure without affecting the legitimate blue. I went to a lot of effort to fix a sample or two
from ~11,000' that Wayne Culbertson took on the Bolivian Altiplano; a lot of work for what was was only partial success.
The solution I came to is to use an 81C filter. That pretty much does away with the UV. However, it also affects the
blue end of the visible spectrum. But that's correctable, whereas the excess UV isn't. As I recall, I made an ICC
profile through an 81C filter, here at sea level. Apply that to a high altitude shot taken with 81C, and all is well,
even if the 81C was more than was needed for the particular situation. This gets away from endless fretting about which
filter to use, never knowing until later.
Plan to bring at least a bit of the delayed digital capture stuff. Moose's
analysis shows that the change in WB was quite subtle at altitude with at
sensor and lenses. With some Panny lenses on Oly
a bit more digging shows that a UV filter will attenuate the purple fringe at
high contrast edges especially in OOF elements. One might presume the purple
blobbies in specular highlights and the fringing might be worse at altitude,
but that is conjecture.
Perhaps it is good to worry just a tad about this.
What MF lenses are you bringing? I have a B+W 55 mm and Vivitar 62 mm 81C filters. I also have a B+W 49 mm KR1.5, which
is, depending on where you look, similar to an 81A or 81B. Also, a 72 mm B+W 010 filter, which has a much sharper
cut-off than the others, although not starting until about 400 nm.
Characteristic curves are here.
<http://www.moosemystic.net/Gallery/tech/UV/Filter%20Curves/>
Kaleidoscopic Moose
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