Step 4 
With everything in your image but the balloons masked out, it’s time to reconvert your RAW file. Double click on the layer thumbnail with your new mask, and ACR will open up. Now reprocess your image with just the balloons in mind—don’t pay attention to the rest. Upping the exposure on the balloons brings out a lot of noise. Since you’re in ACR, you can tone down the noise using ACR’s noise-reduction tools, which work better than those in Photoshop. Click OK to go back to Photoshop.