1. Understanding Focal Length and its Impact:
* Focal Length Defined: The focal length (measured in mm) determines the angle of view and the compression (or flattening) of perspective.
* Common Portrait Focal Lengths:
* 35mm: (Wider Angle) Excellent for environmental portraits. Captures the subject in context with their surroundings. Can sometimes distort facial features if too close.
* 50mm: Considered a "normal" lens, offering a natural perspective similar to human vision. Versatile and good for a range of portrait styles, from headshots to half-body shots. Often affordable and sharp.
* 85mm: A classic portrait lens. Offers good compression, blurring backgrounds beautifully. Flattering for facial features. Requires more working distance (space between you and the subject).
* 100mm - 135mm: Stronger compression than 85mm, further isolating the subject. Excellent for headshots and tight portraits. Requires even more working distance.
* 70-200mm: (Zoom Lens) Highly versatile. Allows you to adjust the focal length for different framing options without physically moving. Excellent compression at the telephoto end (around 200mm). Often more expensive and heavier.
* Compression Explained: Telephoto lenses (longer focal lengths) compress perspective, making the background appear closer and more blurred, thus emphasizing the subject. Wide-angle lenses exaggerate perspective, making the background appear farther away.
2. Considering Aperture (f-stop):
* Aperture Defined: The size of the lens opening. Lower f-numbers (e.g., f/1.4, f/1.8, f/2.8) indicate a wider aperture, allowing more light in and creating a shallower depth of field (more background blur). Higher f-numbers (e.g., f/8, f/11) indicate a smaller aperture, letting in less light and resulting in a deeper depth of field (more in focus).
* Aperture for Portraits:
* Wide Aperture (f/1.4 - f/2.8): Ideal for isolating the subject with a very blurry background ("bokeh"). Excellent in low light. Requires precise focusing as the depth of field is very shallow.
* Moderate Aperture (f/2.8 - f/5.6): A good balance of background blur and sharpness. Suitable for group portraits or when you want some of the background details to be visible.
* Smaller Aperture (f/8 and higher): Used when you want everything in focus (e.g., environmental portraits where the background is important).
3. Factors to Consider:
* Your Style:
* Environmental Portraits: Consider wider focal lengths (35mm - 50mm).
* Classic Portraits (headshots, half-body): 85mm, 100mm, or 135mm are excellent choices.
* Candid/Street Style Portraits: 50mm or a zoom lens can be very useful.
* Your Subject:
* Individuals: 85mm or longer are generally flattering.
* Couples/Groups: You might need a slightly wider lens (50mm or 35mm) to fit everyone in the frame.
* Your Shooting Environment:
* Studio: Any focal length can work, but 85mm and longer are common.
* Outdoors: The environment will influence your choice. Wide apertures are useful in bright sunlight to help control the exposure and maintain shallow depth of field using faster shutter speeds.
* Indoors (smaller spaces): Wider focal lengths might be necessary due to limited space.
* Your Camera System (Sensor Size):
* Full-Frame: Focal lengths are as listed above.
* Crop Sensor (APS-C, Micro Four Thirds): You'll need to consider the "crop factor." Multiply the lens's focal length by the crop factor (typically 1.5 or 1.6 for APS-C, and 2.0 for Micro Four Thirds) to determine the equivalent focal length on a full-frame camera.
* Example: A 50mm lens on an APS-C camera with a crop factor of 1.5 will have an equivalent focal length of 75mm (50mm * 1.5 = 75mm).
* Budget: Lens prices vary significantly. Consider your budget and prioritize features that are most important to you (e.g., image quality, maximum aperture, build quality).
* Autofocus vs. Manual Focus: Autofocus is generally preferred for portraits, especially when shooting with wide apertures. However, some photographers prefer the control of manual focus. Test both options to see what works best for you.
* Image Stabilization (IS/VR): Helpful, especially in low light, as it allows you to use slower shutter speeds without camera shake. Less crucial if you primarily shoot in well-lit conditions or with a tripod.
* Build Quality: A well-built lens will be more durable and withstand wear and tear.
4. Recommendations and Considerations by Price Point (General):
* Budget-Friendly:
* 50mm f/1.8: Often called the "nifty fifty," this lens is incredibly affordable and offers excellent image quality and shallow depth of field. A great starting point.
* Manual Focus Lenses: Brands like Rokinon/Samyang offer fast aperture lenses at more accessible price points, but require manual focus skills.
* Mid-Range:
* 85mm f/1.8: A popular choice for portraits. Sharp, produces beautiful bokeh, and is generally lighter and more affordable than the f/1.4 versions.
* 50mm f/1.4: A step up in light gathering ability and bokeh from the f/1.8.
* Entry-Level 70-200mm f/4: Provides versatility and good image quality at a more reasonable price.
* High-End:
* 85mm f/1.4: The ultimate portrait lens for many photographers. Exceptional image quality, incredibly shallow depth of field, and beautiful bokeh.
* 135mm f/2: Another excellent choice for headshots and portraits with strong compression and background blur.
* 70-200mm f/2.8: A professional-grade zoom lens offering exceptional versatility and image quality. Often a workhorse lens for many photographers.
* Specialty Lenses: Consider lenses with Tilt-Shift capabilities for creative portraiture.
5. Try Before You Buy (If Possible):
* Rent a Lens: Many camera stores and online services allow you to rent lenses for a day or weekend. This is an excellent way to try different focal lengths and apertures before making a purchase.
* Borrow from a Friend: If you have friends who are photographers, ask if you can borrow their lenses to try them out.
* Test in a Store: Visit a camera store and ask to test different lenses on your camera body.
In summary: There's no single "best" portrait lens. The ideal choice depends on your individual needs and preferences. Experiment, research, and find the lens that helps you create the images you envision. Good luck!