Yes... I shot at night with HP5
David, the newly Ilford published correction factors are accurate, but only useful for very careful spot metering en each zone. The former graph in datasheets contains a safety factor of aprox 2/3 stop (for 15s base at least), and it is a good advice for an starting point.
The right correction factors are very sensitive to the way we meter, and to the other factors, so IMHO the old good graph recommends a good starting point.
For example, the graph says that 15s base has to be corrected to 50s, while the new factors say 35s for HP5 and 30s for FP4.
Principal problem with correction factors is that the shadows have more failure than mids and highlights, so one thing is correcting for the scene average illumination and another one is correcting for the shadows.
IMHO if we have a low contrast dull scene the new factors can be used, but with a contrasty scene (urban night) we should apply an additional correction if we want some shadow detail, and in this case the old graph included a lot of wisdom to get our starting point.
Lower correction factors were published by Howard Bond 5 years ago:
http://phototechmag.com/kodak-ilford...te-films-2013/
One has to be careful when comparing LIRF features of different film manufacturers, because ilford used a generous safety margin for good practical results.
Anyway, if one want to do the thng perfect one should calibrate LIRF, this is making contact prints of the Stouffer wedge with known lux, and using also long exposures (15, 30, 60s , 120 for example) and different N+/-. With that information one can guess very well what density he will obtain in the negative for each scene metered spot. I made some informal tests in this way, enough to see that full calibration it's interesting for night shots.
Let me repeat, IMHO new factors are useful for accurate metering, if one wants to use spot metering in the shadows to know in what density it will end a "zone" in the negative, but better make calibrations with the Stouffer. If it's not the case, better to start with the old graph, because that safety margin is benefical to conserve shadows.
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