Hi, all.
>on 9/05/2005 07:32, Andrew Fildes at afildes@xxxxxxxxxxxxxx, wrote:
>> Never sure what the KR means but a KR3 is much 'warmer.'
Dear colleague ;-), I think that K stands for 'correction' (in German
spelling!) and R for 'red' -- there's another line of bluish KB filters.
The number is the correction strength in deca-MIREDs; a KR 1.5 then
corrects colour 'temperature' by +15 MIRED.
BTW, 'MIRED' means 'MIcro REciprocal Degrees' -- that's a more 'natural'
measure of colour 'temperature'. For instance, the typical 5600 K daylight
would equal to:
1000000 / 5600 = 180 MIRED (approx.)
But the typical 3200 K tungsten light would be:
1000000 / 3200 = 310 MIRED (approx.)
The odd thing of the Kelvin scale is that a *warmer* ('more' temp.) light
has a *lower* (?) temperature -- unlike MIRED, which results in a *higher*
figure.
>From: Fernando Gonzalez Gentile <fgnzalez@xxxxxxxxxxxxx>
>Just did a little googling and to my surprise, the KR 1.5 corrects
>temperature from 3400 to 3200 K,
3400 K => 295 MIRED. If we add +15 MIRED (the KR 1.5)... voilà! we've got
295+15 = 310 MIRED => 3200 K (remember previous paragraph?). MIRED makes
life so easy... :-)
>which would be a Sky 1A equivalent.
I don't think so... the 1A has a pinkish tone, instead of the pale brown of
the KR series -- but you already knew that!
>But the 81a seems to correct from 3400 to 3200 too !!
Then KR 1.5 <=> 81A.
>Looking at it, it looks quite brownish - and my Hoya Sky 1a looks rather
>pink, with green relections due to multicoating.
Sure...
>Looking through it, it seems to warm up much more noticeable than the Hoya.
That's right -- and the 1A needs *no* exposure compensation, not even the
slight x1.1 of the KR 1.5 / 81A (something like 1/6th of a stop, according
to my calculations)
>That's why I thought it was a 81a - but the table at the link above lists KR
>filters as different to the 81a & 81b.
I beg your pardon? If the same correction is made, that should be the very
same filter -- only danomination (B+W vs. Kodak Wratten) is different.
Abrazo / Hug,
...
Carlos J. Santisteban
<cjss@xxxxxxxxxxxxx>
<http://cjss.galeon.com>
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