1. Aperture (f-number):
* The Lower the f-number, the Shallower the Depth of Field: This is the single most important factor. Use a wide aperture (e.g., f/1.4, f/1.8, f/2.8, f/4). These small f-numbers create a shallow depth of field, meaning only a small portion of the image will be in sharp focus, and the background will be blurred.
* Lenses: Lenses with wide maximum apertures (f/1.8, f/1.4, f/1.2) are specifically designed for creating shallow depth of field and are highly desirable for portrait photography. Faster lenses (lower f-numbers) tend to be more expensive.
2. Focal Length:
* Longer Focal Lengths Create More Blur: A longer focal length (e.g., 85mm, 135mm, 200mm) compresses the background and magnifies the blur. This is because longer lenses have a shallower depth of field *at the same aperture* compared to wider lenses.
* Portrait Lenses: Focal lengths in the 85mm to 135mm range are often considered ideal for portraiture, providing a flattering perspective and good background blur. 70-200mm zoom lenses are versatile and popular for portraits.
3. Distance to Subject and Background:
* Get Close to Your Subject: The closer you are to your subject, the shallower the depth of field, and the blurrier the background will be.
* Maximize Distance Between Subject and Background: The farther your subject is from the background, the more blurred the background will appear. Putting more space between your subject and the background gives the lens more room to render the background out of focus. Imagine your subject is standing right in front of a wall versus standing several yards away from the wall – the wall will appear much blurrier in the second scenario.
4. Sensor Size (Crop Factor):
* Larger Sensors Produce Shallower Depth of Field: Cameras with larger sensors (e.g., full-frame) generally create shallower depth of field than cameras with smaller sensors (e.g., APS-C, Micro Four Thirds) *at the same aperture and focal length*.
* Crop Factor Consideration: If you're using a camera with a crop sensor, you'll need to use a shorter focal length lens to achieve a similar field of view as a full-frame camera. For example, an 85mm lens on an APS-C camera with a 1.5x crop factor will have a field of view equivalent to a 127.5mm lens on a full-frame camera. To get a similar blur as a full frame 85mm you might select a 50mm or 35mm lens and adjust your distance to the subject to get a similar composition.
Putting it All Together - Steps to Achieve Blurred Backgrounds:
1. Choose a Lens with a Wide Aperture: Prioritize lenses with a maximum aperture of f/2.8 or wider (lower f-number).
2. Select a Longer Focal Length: Lenses in the 85mm to 135mm range are ideal, but experiment with what you have. Zoom lenses in this range offer versatility.
3. Set Your Aperture: Dial in the widest aperture available on your lens (e.g., f/1.8, f/2.8). Be mindful of your subject's features, to ensure their eyes (or the features you want sharp) are within the depth of field.
4. Position Your Subject:
* Move closer to your subject.
* Position your subject as far away from the background as possible.
5. Focus Carefully: Use single-point autofocus (or manual focus) and focus precisely on your subject's eyes (usually the closest eye).
6. Compose and Shoot: Take your picture and review the result. Adjust your settings (aperture, distance to subject) and reposition your subject if necessary.
Additional Tips:
* Background Quality: The quality of the background is important. Points of light in the background (e.g., streetlights, sunlight filtering through trees) will turn into beautiful bokeh balls when blurred. Avoid backgrounds that are too cluttered or distracting, even when blurred.
* Lighting: Good lighting enhances any portrait. Soft, diffused light is generally flattering.
* Tripod (Optional): A tripod can be helpful, especially when using longer focal lengths or shooting in low light conditions.
* Practice: Experiment with different combinations of aperture, focal length, and distance to see how they affect the depth of field and background blur. The best way to learn is to practice!
* Manual Mode (M): Using manual mode gives you the most control over your settings, allowing you to precisely adjust aperture, shutter speed, and ISO to achieve the desired exposure and depth of field. Aperture Priority (Av or A) mode is also useful, allowing you to set the aperture and let the camera automatically choose the shutter speed.
* Check Sharpness: When shooting at wide apertures, depth of field is very shallow. Use your camera's zoom function to check the sharpness of your subject's eyes after taking a photo.
By understanding these principles and practicing regularly, you can consistently create portraits with beautifully blurred backgrounds that draw the viewer's attention to your subject.