Reciprocity failure and Fuji 100C?

[winger]

If I were doing an exposure using Fuji100C that metered as f16 for 15 seconds, how much should I adjust if any? I'm getting shots that still look dark compared to the scene, but I don't want to go just by guessing. I've used 20 seconds and 25 seconds. My favorite, best-ever app for this has every film I've ever used, but not instant film.

 

[Lee L]

The attached should help.

Lee

 

[Lee L]

Ran the numbers from the Fuji datasheet. Schwarzschild exponent calculates consistently to 0.5 at all the given data points.

To calculate an adjusted exposure time (not aperture adjustment) it's:

corrected exposure time in seconds = (t+1)^(1/p)-1

where t is the metered exposure time in seconds and p is the Schwarzschild exponent

Chart attached. Have fun.

Lee

 

[winger]

Thanks, Lee!

 

[Lee L]

You're welcome. I look forward to seeing the results.
I revised the chart with a monotype font for a better reading table. Newly installed version of LibreOffice defaulted to Arial, horrible for this purpose, and looked worse in the .pdf. So you may want to download again.

Lee

 

[Lee Rust]

Yes, thanks for this very useful chart.

 

[winger]

I shot these before I had Lee's chart. The darker one (done first) was at f16 for 20 seconds. The lighter one was f8 for 20 seconds.