As a general rule to portrait and macro photography, one needs to blur the background to eliminate distractions from the main subject whether a flower, a head shot, or an emphasised object. To accomplish this in camera you need to have a quick glass i.e. an aperture of f/4 or less and a subject far away from the background. Ideally a focal length of 85 mm will produce good results.
Whether you don’t have this glass in your arsenal or you want to eliminate further distracting elements in your photo, you can achieve this effect in post-processing. Adobe Lightroom comes equipped with three different tools in the Develop Module:
- The Brush Adjustment (LR v 3 and above)
- The Graduated Filter (LR v 3 and above)
- The Radial Filter (LR v 5 and above)
Basically use the adjustment brush or the graduated filter or the radial filter with the Sharpness slider reduced to between -50 and -100. If this is not enough blur, add another adjustment (brush or filter) and repeat the process until you achieve the effect you are looking for. Just click on New to start a new adjustment and paint or apply a filter one more time.
If you made an error during the process and you want to erase or reduce the effect just hold down the Alt key on Windows or Option key on Mac and brush the pixels you want to keep sharp.
The result is a shallower depth of field as if captured by the camera.