How to convert a color image to black and white using Grayscale command -(Destructive method)

There are  various ways of converting an image from colored to Black and White.Here we shall discuss the method that is destructive which means that the method makes changes directly to the image.The advantage of using this method is that it is very quick.

                                                              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.

We can see the image opened as a Background layer in the Layers Panel.
2) Selecting the Grayscale option

After we see the image in Photoshop window we need to select the Grayscale option.

Select menu Image > Mode > Grayscale

3)Confirmation Dialog box
Now Photoshop will open a message dialog box asking us to confirm that we want to discard the color information of the image.It will also suggest that to control conversion we use menu Image > Adjustments > Black & White... Click on Discard button.

This will remove the color from the image instantly and turn it to black and white.
In case we are not satisfied with the change we can go back to the original image at this point by using the menu Edit > Undo Grayscale command or by using keyboard shortcut Ctrl + Z.
We can also use the menu Edit > Step Backward or the keyboard shortcut Alt+Ctrl+Z.

4)Saving the image

After we are satisfied with the adjustments we will save the image by selecting the menu File > Save or 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 once we save the image we cannot get the original colored image again.Also we have no control over the conversion.