[LargeFormat] Reciprocacy of Polaroid film (type 54)

[Clive Warren]

At 10:56 am +0000 4/12/01, mark.blackman1@btinternet.com wrote:
>There was a programme on TV this saturday about a 'haunted' castle 
>in England. I decided to demonstrate to my kids how easy it is to 
>take a photo of a 'ghost' using double exposure. I took a reading of 
>a suitably gloomy part of the house which indicated an exposure of 
>15 secs at f16 for 100 asa - I was using a polaroid back with 
>Polapan Pro 100 b&w film. I guessed a reciprocacy of around 4x, so 
>took two shots of 30secs each.
>
>Needless to say, all I got was nothing! What is the sort of factor I 
>should use for this film at longer exposures? For info, the camera 
>used was an Ebony RW45 III.

Mark,

Have not used this film at such long exposures but guess that it 
really suffers quite badly from reciprocity failure. Am surprised 
that you had nothing on the print though. Do you mean that the print 
was blank with no signs of exposure?  Are you sure the darkslide was 
pulled out? ;-)

Cheers,
        Clive