To convert a color photograph to black-and-white, go to the Develop module, and do the following.
There are three "stops" on the way to a black-and-white photograph.
First . . .
1) Press Ctrl + '.
You'll convert the virtual copy to black-and-white.
Your color original is available for locating areas of color to be edited in the black-and-white version.
2) In the Basic panel, under Treatment, select Black & White.
By default, Lightroom applies an Auto setting in the HSL/Color/B&W panel.
In most cases, the photograph will need more work.
2) Go to the HSL/Color/B&W panel and click the B&W section.
The sliders will have been adjusted by Lightroom.
You can modify the grays by using the sliders.
For example, let's say you're editing a photograph with a blue sky.
Use the Blue slider to change how the blue sky looks in the black-and-white version.
You can also click the target icon in the upper-left corner of the section.
Position your cursor over a gray area that has a fairly uniform color in the original color photograph.
Click, hold, and move the cursor up and down.
Lightroom will select the color in that area, and will modify the sliders accordingly.
When you're finished, click the Done button located below the photograph on the right end.
Let's say you:
• Already have a black-and-white photograph.
• You didn't convert it to black-and-white from color.
The photograph's file may not have color information.
If so, you won't be able to modify the tones by modifying the colors, as described above.
3) Return to the Basic panel.
4) Use the tools to further adjust the tonal values of the photograph.
There are many presets for black-and-white photographs.
Go to the Presets panel on the left side of your screen in the develop module.
You can set Lightroom to not apply the Auto adjustment when you click Black & White in the Basic panel.
Go to Edit > Preferences (Windows) or Lightroom > Preferences (Mac).
Click the Presets tab.
Deselect Apply auto mix when first converting to black and white.