Here are three black & white images derived from a single Adobe RGB color file. Each monochrome shot was created using a different b/w conversion method.

 
B/W done with HSL/G in Camera RAW

 
 
B/W done with Channel Mixer (same results as "Black and White") adjustment.

 

Conversion done in Camera RAW, blended with Smart Object layers (3 layers)

 
Original Color Image