I’m a big fan of the PKS plugin but one limitation for b/w photographers is that it only works on RGB images. You must convert from grayscale to RGB to apply the sharpening and convert back to grayscale.
To avoid introducing rounding or quantization errors that may degrade image quality during these roundtrip conversions you need to make sure that both the RGB and grayscale space share the same gamma value. This tutorial shows you how to do just that.
Custom Gamma tutorial

Hi Mister Diallo.
Nice job and interesting presentation of your web action. I would like to add a remark about it. I hope you 'll dont mind. When you select the batch process, you propose to rename the new jpegs files begining by "client spec" in the first file naming field. May I propose to all the readers to put a "_" character intead of a " " space because on the web server, the file named as client spec01.jpg has (to me) not a chance to get linked correctly (except if you link to spec%20client02.jpg in your page).
Hope you will not be upset by this pertinent remark.
Christophe from Paris-France

Christophe,
You make an excellent point about files destined for the web. Either an "_" as you suggest of simply closing up filenames (no spaces) are very good habits.