Reciprocity Failure

I seem to shoot a lot of film these days (keeps me interested in photography when I’m not able to photograph the subject matter I’m actually interested in), hence all the film landscape shots!

Recently I discovered the Law of Reciprocity the hard way. Reciprocity failure – defined as the non-linear decrease in light sensitivity (speed) of a film at the extremes of very short and very long exposures times. In real terms this means for long exposures a correction factor must be added to the exposure time in order to correctly expose a scene.

I’ve been shooting a series of pictures of Wellington at night using Fuji Velvia 50. For Velvia 50, any exposures longer than 1 second need to have the exposure times corrected to reflect the Law of Reciprocity. So for a marina lit by a full-moon at f8 with a 30 second exposure, would need a correction of 1 stop. Exposures beyond 32 seconds are not recommended. Being a slide film, Velvia only has an exposure latitude of 1/2 stop meaning that if my exposure is off by more than half a stop, you end up with an image that looks very much like this:

Chaffers Marina, Wellington under a full moon. Velvia 50 (120 roll) with an exposure of around 30-45 seconds

 

I was so horrified after paying $50 or so for developing two 120-rolls of Fuji Velvia, I switched to Fuji Provia instead. Reciprocity failure occurs with Provia at exposures longer than 128 seconds. My second attempt at producing a moonlit shot of Chaffers Marina looks like this:

Chaffers Marina, Wellington under a full moon. Fuji Provia (120 roll) stitched panorama.

I will go back to playing with Velvia now I know what I’m doing!