Overexposing black and white

[Jarin Blaschke]

As standard practice, I usually rate color film lower than the factory setting to enrich contrast, reduce apparent grain and gain good, strong blacks. It's also a type of exposure safety. I will be shooting an upcoming black and white piece and I'm wondering if this is still good practice. I imagine I'll likely get good blacks, but I've heard that grain actually increases when 'over' exposing black and white. Is this true? What else might I expect?

 

Thanks.

[John Pytlak RIP]

With a B&W camera negative film, graininess does increase slightly with increasing exposure. Here is the granularity curve for 5222 (RMS granularity is the red curve):

 

http://www.kodak.com/US/plugins/acrobat/en...es/5222Diff.pdf

 

And 5231:

 

http://www.kodak.com/US/plugins/acrobat/en...es/5231Diff.pdf

 

Best to give a "normal" exposure at the rated EI. Underexposure will give lower density "smoky" blacks in the final print, where grain will be more visible. But gross overexposure will put scene information (especially highlights) on a grainier portion of the film's characteristic curve.

[Dominic Case]

But gross overexposure will put scene information (especially highlights) on a grainier portion of the film's characteristic curve.

John I know this is true - but can you explain _why_ the highlight part of the curve is grainier in b/w emulsions? It's different from the way colour emulsions work.