1. Aperture (f-stop):
* The Lower the Number, the Shallower the Depth of Field: Aperture is the size of the lens opening. It's measured in f-stops (e.g., f/1.4, f/2.8, f/4, f/5.6, f/8, f/11). The lower the f-stop number, the wider the aperture, and the shallower the depth of field (DOF). This means only a small area in front of and behind the focus point will be sharp, while the background will be blurred.
* Ideal Apertures for Portrait Blur: For significant background blur, aim for apertures like f/1.4, f/1.8, f/2, f/2.8, or f/4. The exact aperture you use will depend on the lens, the distance to your subject, and the desired level of blur.
2. Focal Length:
* Longer Focal Lengths Compress Depth: Longer focal lengths (e.g., 85mm, 135mm, 200mm) create a shallower depth of field and compress the background, making it appear even more blurred.
* Recommended Portrait Lenses: Popular portrait lenses are typically in the 50mm to 200mm range. An 85mm lens is a classic choice. Longer lenses are generally preferred if you have enough space to work with.
* Why it works: Longer focal lengths magnify the subject and background more, effectively magnifying any blur in the background.
3. Subject Distance:
* Get Closer to Your Subject: The closer you are to your subject, the shallower the depth of field will be. This means more background blur.
* Don't Get *Too* Close: Getting too close can distort facial features, especially with wider-angle lenses. Find a comfortable distance that suits your lens and composition.
4. Background Distance:
* Increase the Distance Between Your Subject and the Background: The further the background is from your subject, the more blurred it will appear. Put as much space as possible between your subject and the background.
* Strategic Background Placement: Look for backgrounds that are already naturally out of focus due to distance, such as foliage, lights, or textures far away.
5. Sensor Size (Camera Body):
* Larger Sensors, Shallower Depth of Field: Cameras with larger sensors (e.g., full-frame) generally produce shallower depth of field compared to cameras with smaller sensors (e.g., APS-C, Micro Four Thirds). This is because larger sensors allow for the use of lenses with wider apertures and create more opportunities for background compression.
* Crop Factor: If you are using a crop sensor camera (e.g., APS-C), you can still achieve background blur, but you may need to use wider apertures or longer focal lengths to compensate for the crop factor. You need to calculate the equivalent focal length. For example, if you use a 50mm lens on an APS-C sensor with a 1.5x crop factor, the equivalent focal length is 75mm (50mm x 1.5).
In Summary (The Magic Formula):
* Wide Aperture (low f-stop number)
* Longer Focal Length
* Close Subject Distance
* Far Background Distance
* (Bonus) Larger Sensor Size
Practical Tips and Techniques:
* Shoot in Aperture Priority Mode (Av or A): This mode allows you to set the aperture, and the camera will automatically choose the appropriate shutter speed.
* Manual Mode (M): Gives you full control over both aperture and shutter speed, allowing for precise exposure control.
* Focus Carefully: Accurate focus on your subject's eyes is crucial. Use single-point autofocus or eye-detection autofocus if your camera has it.
* Consider Your Composition: Think about how the blurred background complements your subject. Look for backgrounds with interesting shapes, colors, or light. Avoid distracting elements.
* Use a Fast Lens: A lens with a wide maximum aperture (e.g., f/1.8, f/1.4) is essential for achieving significant background blur. These are often called "fast" lenses.
* Experiment and Practice: The best way to master background blur is to experiment with different settings and compositions. Take lots of photos and review them to see what works best for you.
* Post-Processing (as a last resort): While it's always best to achieve the desired effect in-camera, you can use software like Photoshop or Lightroom to add artificial background blur. However, this often looks less natural than genuine bokeh.
Example Scenarios:
* Shooting indoors with limited space: Use a wide aperture (e.g., f/1.8) and get as close to your subject as possible while still maintaining a flattering composition. Position your subject so that the background is as far away as possible.
* Shooting outdoors in a park: Use a longer focal length lens (e.g., 85mm or 135mm), a wide aperture (e.g., f/2.8), and position your subject in front of foliage or trees that are far away.
* Shooting a close-up portrait: Use a macro lens or a lens with good close-focusing capabilities, a wide aperture, and focus carefully on the eyes.
By understanding these principles and practicing regularly, you can consistently create beautiful portraits with stunning blurred backgrounds.