Rollei Films Reciprocity Failure.

Hi,

 

does anybody know where I can find info on the reciprocity failure of the new Rollei's films?

 

Thanks for looking / helping,

 

Antonio

R3 is about the same as Tri-X. Double exposure at one second or more and pull just a little.

Indeed, which is correct. The Rollei Retro films are exactly following the APX 100/400 characteristics, not so strange because it's the same emulsion.

About PAN 25 the reprocity failure was never measured. It will follow approx. the OrWo NP15 measurement which was a theoretically measurement at that time.

 

The IR 820/400 will follow approx. the APX400 curve.

Thank you very much.

Next Week i'll do a trial and I let you know as soon as films will have been developped.

Thanks Again,

 

Antonio

"R3 is about the same as Tri-X. Double exposure at one second or more and pull just a little."

 

If this is true, then the general equation for reciprocity correction is:

 

Tc = Tm ^ 1.62 + Tm

Tm = value from exposure meter.

Tc = value corrected for reciprocity non-linearity.

It's better to use a known value of a longer exposure. Otherwise extrapolation errors from the small value can mess you up. If you know from valid experiment how much to add when metered exposure Ti is, say, 10 seconds, divide the amount to be added by Ti ^ 1.62 to get a value we'll call f. Then the amount to be added for any other value of Ti will be Ti ^ 1.62 * f.