Ilford reciprocity departure Graphs

[WAn]

The mentioned graphs, published in Ilford film data sheets, seem to

be pretty much the same (see attached graph). I wonder do the old

type films (HP5+, PanF+, FP4+) and films of the new type (Deltas)

really have so similar, not to say identical reciprocity

characteristics?

 

 

Thanks

Andrey

[tom_westbrook]

I think you have to take their word that reciprocity is as they say it is. Test & adjust if you don't like the results. I'd personally rather have uniform reciprocity characteristics than have to remember them for each film I use.

[richard_ilomaki]

Andrey

 

The graph is only an approximation. I shot some HP5 yesterday and the meter said 16 secs., so I shot 2 sheets-one at 32 secs and the second at 60 secs. The second one was overexposed quite a bit. What likely happened was that it was cold outside- minus 5 C. and the lower temp may have affected the recip failure. Just one example of what can vary, and why I usually shoot two sheets.

 

Astronomers have known for a long time that cooling the film lessens the recip failure. Some astro cameras use dry ice behind the film to cool it.

 

Cheers