|Ultrafine/Kentmere 100 Reciprocity Test-Camera: Fuji G617, Film Ultrafine (E)Xtreme 100, ND-9+red @ f22 140 seconds|
If you are interested in long daylight exposures, you may have run in to the same problem I have. Say you have your camera all set up, the clouds are whisping by, and you want to get that long daylight blur thing going. You figure a 30 second exposure (approx.) would be ideal. Well how do I get there?
I've got a bunch of filters: a 4 stop ND, a 9 stop ND, as well as a red, yellow, and orange filter. It's mid day and my meter reading says 1/125th @ f16. I start counting with my fingers: -1 stop = 1/60th, -2 stop = 1/30th, and so on. So then I get down to 4 seconds with my darkest ND filter. If I stack both my ND filters, I get down to 30 seconds where I wanted to be. But wait! That's without reciprocity corrections. Great if I had Acros for film. But I don't and it's being retired soon, so I wont have access to it at all.
What I ended up making was this spreadsheet that accounts for reciprocity failure and spells out exposures using sunny 16 rules. So now I can look at my chart here (see below), look in the sunny category, find my desired time and apply the right filter. So, for example I can get to about 30 seconds by using my 9 stop ND + an orange filter to get to 28 seconds including reciprocity failure corrections. Look at the bottom of the chart for filter combinations.
This chart is specific to a given film: in this case I've used Kentmere/Ultrafine 100. I plan to add the entire Harman/Ilford film line to the list over time. If you want me to add a film, or if you want the table with the reciprocity correction formula just let me know!