Re: [APML] Pushing Provia 400F - Actual Speed Gain?

[Wei-Hao Wang <whwang@gmail.com>]

Hi Wade,

Please come to this directory:
http://www.ifa.hawaii.edu/~wang/chinese/articles/wide_field_astrophoto/tone_control.files
There are five JPG files.  The file names explain themselves.  

These images were taken at the same night with the same lens, on Provia
400F of course.  The sky condition was not too perfect and there might be 
some background brightness and transparency variations.  Nevertheless, I 
believe it is fair to say that 20min nopush and 10min push+1 give very 
similar densities.  In other words, Provia 400 push+1 does have EI=800, 
which is what Fuji tells us.

As I understand, in terms of film speed, the effect of pushing has nothing to 
do with long exposures.  I believe here you are talking about
reciprocity failure.
Reciprocity failure controls how fast latent image forms on the unprocessed
film.  Processing controls how the latent image is transformed into density.
These two are pretty much independent.  You can do some pushing tests
under short exposure times (no reciprocity failure), as the film company does.
The result should apply to long exposure times (with reciprocity failure).

Cheers,

Wei-Hao

-- 
________________________________________________________________
Wei-Hao Wang  :)

Institute for Astronomy at University of Hawaii

Address:                       
2680 Woodlawn Drive         Personal Website:
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