[alt-photo] Re: Ultra Long Exposure Reciprocity Failure?

[Loris Medici]

Geoff, from now on I'll switch to your formula below; it gives
slightly more exposure than T^1.48 (negligible), but I would
definitely prefer to err towards overexposure than underexposure...

See some comparisons below:
30 secs., T^1.48 = 153 secs., T x sqrt(T) = 164 secs. (diff. in stops = 1 / 10)
60 secs., T^1.48 = 428 secs., T  x sqrt(T) = 465 secs. (diff. in stops
 ~= 1 / 10+)
120 secs., T^1.48 = 1195 secs., T  x sqrt(T) = 1315 secs. (diff. in
stops  ~= 1 / 7)

Thanks for sharing!


2012/1/20 Geoff Chaplin <geoff at geoffgallery.net>:
> If t is the metered time in seconds the t x root(t) works for FP4+ and Adox
> up to a couple of hours or so (t = 400 sec or so).