How to convert a colored image to black and white using Hue/Saturation layer in photoshop CS6 - (Non Destructive)

There are  various ways of converting an image from colored to Black and White.Here we shall discuss the method that is non destructive which means that the method does not make any changes to the image.Photoshop uses a separate Hue/Saturation layer to apply the adjustments.
                                       

                                                              Before                After
1) Opening the image in the Photoshop window

Open the colored image in Photoshop CS6 by using the menu File > Open or by using the keyboard shortcut Ctrl + O.This will open a dialog box.Select the image by clicking on its name and click on Open button.

This will open the image as a Background layer in the Layers Panel.
2) Selecting the Hue/Saturation... option

After we see the image in Photoshop window we need to open the Hue/Saturation  properties window.For this we need to select the  Hue/Saturation option.There are two ways of selecting the  Hue/Saturation option.

a) Select menu Layer > New Adjustment Layer >  Hue/Saturation... 

We can see a dialog box asking the name of the new adjustment layer.By default Photoshop names it  Hue/Saturation 1.If we want we can type in any other name or we can leave it as  Hue/Saturation 1. Click on OK button after naming the layer.

 b) The other way to get the  Hue/Saturation option is by clicking on the Create new fill or adjustment layer icon (half colored circle) in the bottom of the layers panel and selecting  Hue/Saturation... option.
                                                         
                                                
3) Hue/Saturation Properties panel

a)Setting saturation value to -100
Now we can see a  Hue/Saturation Properties panel with sliders for Hue,Saturation and Lightness.We need to drag the Saturation slider towards the leftmost corner till saturation value reaches -100.We can observe that the color of the image has become black and white.
                                                         

b)Exiting out of Hue/Saturation Properties panel
To hide the Hue/Saturation Properties panel click on the double pointing arrow on the top right of the properties panel.To exit out of the Hue/Saturation Properties panel click on the cross mark on the top right corner of the properties panel or click on the down pointing arrow at the top right corner of the properties panel and select close.

4)Layers Panel
We can see a new layer with a thumbnail (rectangle divided into two parts and the upper half of the rectangle divided into three parts)added just above the image layer in the layers panel on the right side of the photoshop window.
                                                                              

5)Saving the image

After we are satisfied with the adjustments we will save the image by selecting the menu File > Save or by using the keyboard shortcut Ctrl + S.This will open a dialog box where we can write the name of the image.After typing a name click on Save button.

The disadvantage of using this method is that we have no control over the adjustment.