Converting Part of an Image to B&W Using Masks

Topics Covered in This Lightroom Tutorial:

Master the Auto Mask Feature, Create Selective Black & White Effects in Foregrounds, Transform Backgrounds with Precision Color Removal

Exercise Preview

Exercise Overview

In this exercise, we'll harness the precision of Lightroom's Adjustment Brush tool to create sophisticated selective color effects. You'll learn to isolate specific areas of your image—leaving some elements in vibrant color while converting others to striking black and white. This technique remains one of the most powerful ways to direct viewer attention and create dramatic visual impact in your photography.

The selective desaturation approach we'll explore here gives you far more control than global adjustments, allowing you to make nuanced creative decisions that can transform an ordinary photograph into a compelling artistic statement.

Making the Tree Black & White

1. Navigate to the Library module to begin organizing your workspace.

2. Expand the Catalog panel on the left sidebar if it's currently collapsed—this gives you quick access to your entire photo collection.

3. Click on All Photographs to view your complete image library.

4. Select the photo of the tree branch (20110831_YourName_039). If this image isn't visible in your catalog, you'll need to complete Exercise 1A: The Library Module first to properly import your practice files.

5. Press D to seamlessly transition into the Develop module, where all the creative magic happens.

6. Locate and click the Adjustment Brush tool in the tool strip on the right panel. This powerful tool allows for precise, localized adjustments.

7. In the tool options panel below the Adjustment Brush (scroll up if necessary), double-click the word Effect to reset all sliders to their neutral zero position. This ensures you're starting with a clean slate for your adjustments.

8. Now we'll create our selective effect by painting negative saturation directly onto the tree branch, leaving the surrounding elements untouched. Drag the Saturation slider all the way to the left to -100. This extreme setting will completely remove color from any area you paint.

9. Expand the Brush panel (located under the Effect panel) if it's not already visible—this gives you access to crucial brush behavior settings.

10. Ensure that Auto Mask is checked. This intelligent feature is game-changing—it automatically detects edges and similar tonal areas, preventing your effect from bleeding into adjacent areas. Think of it as having a built-in edge detection system that keeps your adjustments precisely where you want them.

11. Before you begin painting, optimize your brush size using these essential keyboard shortcuts:

    Left bracket ( [ ):	Reduces brush size for detailed work
    Right bracket ( ] ):	Increases brush size for broader coverage

12. Begin painting over the tree trunk with deliberate strokes. The key to success with Auto Mask is keeping the crosshair (+) symbol well within the boundaries of your target area—in this case, the trunk itself. As long as you keep that crosshair inside the trunk's edge, Auto Mask will prevent the desaturation from spilling into the sky background. If you accidentally desaturate some background areas, don't worry—we'll refine the mask in the next steps.

13. Press O to toggle the mask overlay, which displays your painted area as a red tint. This visual feedback is invaluable for seeing exactly what you've affected.

14. With the mask visible, identify any areas of the tree branch you may have missed and paint over them to complete the effect.

15. If you've accidentally painted beyond your intended area, use these refinement techniques to perfect your mask:
    • Navigate to the Adjustment Brush options panel on the right side.
    • In the Brush section, click the Erase option to switch to removal mode.
    • Carefully paint over any background areas to remove the unintended black and white effect.

    If your correction work accidentally removes the effect from parts of the tree trunk you want to keep desaturated:

    • Return to the Adjustment Brush panel and select Brush A to switch back to application mode.
    • Re-apply the mask to the affected tree areas.
    • Pro tip: Hold down Opt (Mac) or ALT (Windows) while painting to instantly access the erase function without switching tools.
    • Use the bracket keys to fine-tune brush size—smaller brushes give you surgical precision for edge work.
    • Work with a smaller brush size when refining edges for the most professional results.

16. Press O again to hide the mask overlay and reveal your finished selective color effect. The contrast between the monochrome tree and colorful background creates immediate visual drama.

Now that you've mastered the fundamental technique, let's explore the inverse approach for an entirely different aesthetic impact.

Making the Background Black & White

This alternative approach creates an equally compelling but distinctly different mood—keeping your main subject in vivid color while rendering the background in elegant monochrome. This technique is particularly effective for isolating subjects and creating a more contemporary, editorial look.

1. Navigate to the History panel on the left and click on the original import state (the bottom entry beginning with Import). This resets your image to its unedited state while preserving your previous work in the history stack.

2. Reselect the Adjustment Brush tool from the right panel if it's not already active.

3. Verify that your Saturation slider is positioned at -100 (all the way left). If the setting has reset, drag it back to the extreme left position.

4. Press the right bracket ( ] ) multiple times to increase your brush size substantially—you'll be covering much larger areas than in the previous exercise.

5. Press O to activate the mask overlay before you begin painting. This preview mode helps you see your progress as you work.

6. Begin painting over the background areas, working systematically around the tree. The Auto Mask feature continues to work in your favor—as long as you keep the crosshair symbol away from the tree's edges, the intelligent masking will automatically detect and preserve the boundary between subject and background.

7. Fine-tune your mask using these professional techniques:
   • To remove any unwanted mask areas, hold Opt (Mac) or ALT (Windows) and paint over the sections you want to restore to full color.
   • For intricate detail work around complex edges, reduce your brush size and consider zooming in for pixel-level precision.

8. Press O to hide the mask overlay and evaluate your selective color effect. The vibrant tree against the monochrome background creates a completely different emotional impact than the previous version.

9. At the bottom of the Adjustment Brush options panel, locate the Switch icon (positioned to the left of Reset | Close). Click this to toggle between your before and after views—an essential step for evaluating the strength and effectiveness of your adjustments.

10. Click the Done button to finalize your adjustment and return to the standard Develop interface.

11. For a final comparison of your work, click the Before & After icon to display both versions side by side. This split view showcases the dramatic transformation you've achieved using nothing but selective saturation adjustments.