Murray Leshner wrote:
>I have seen a number of b/w films that have a base 10
>log response to long exposures:
>
>0 stop at 1 second; logten of 1 = 0
>1 stop at 10 seconds; logten of 10 = 1
>2 stops at 100 seconds; logten of 100 = 2
>
>Fuji Superia (cheapo 35 mm 4-packs 200 ISO) is 1/3
>stop for 4 seconds, 2/3 stop for 16 seconds, 1 stop
>for 64 seconds. I see a pattern here too; looks like
>0.5 scaling factor from above, with roundoff to
>fractional stops rather than 0.3, 0.6, 0.9 that come
>from log of 4, 16, 64).
>
>Interestingly, some charts say NO RF correction for
>Kodak C41 chromogenic B/W...hmmm.
>
>If you have no RF correction info at all for a given
>film, other than the C41 example above, I'd estimate
>adding a number of stops equal to somewhere between
>the 1/2 and 1 times the log-base10 of an exposure
>greater than 1 second.
>
>I've promised to share a spreadsheet (open source? for
>public enhancement) that pre-charts long exposures
>based on EV and Zone placement. It includes a RF
>correction scaled to a particular film based on one
>datum pair (correction at given exposure time) entered
>by the user. I don't know how ideal it is, or how
>precise it really needs to be for long exposures.
>
>
>I keep getting distracted and busy, but I'll work on
>it.
>
>I may be making it much more complicated than
>necessary, but that's my nature.
>
>Murray
>
Try David Balihar's Pinhole Designer:
http://www.pinhole.cz/en/pinholedesigner/
He already has a large collection of RF for different films
taco
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Received on Tue Mar 22 15:41:55 2005
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