XnView Software

For those interested :
To avoid the above mentionned problem, you must modify the PS gray workspace : from "dot grain 15%" (default value) to "gray gamma 2.2"

I've continued to investigate towards PS (thank to MaxSt for the idea!) and I noticed that the problem is only for the greyscale pictures resulted from a RGB to greyscale conversion done with PS. If the picture is originally a greyscale picture, PS and XnView read the picture in the same way ...

I forgot to mention that XnView is running under Windows XP SP3
Sorry

The Greyscale B&W pictures (8 bits) read by XnView are darker than those read by PhotoShop.
I tried to know why. My diagnosis is the following : XnView does'nt read properly Greyscale pictures.
Indeed, if I compare un greyscale chart read by PS and by XnView, I notice the following results :
read by ...