1. Focal Length:
* Why it Matters: Focal length drastically affects compression, perspective, and the distance you need to be from your subject.
* Popular Focal Lengths for Portraits:
* 35mm: (APS-C: ~24mm)
* Pros: Versatile, good for environmental portraits (showing the subject in their surroundings), wider field of view.
* Cons: Can distort facial features slightly if you get too close, not ideal for tight headshots.
* 50mm: (APS-C: ~35mm)
* Pros: Considered a "standard" focal length, close to human perspective, good for a variety of portrait styles. Often sharp and relatively inexpensive.
* Cons: Requires you to be moderately close to your subject, may not offer extreme background blur.
* 85mm: (APS-C: ~56mm)
* Pros: Considered by many the "classic" portrait focal length, excellent compression, flattering perspective, creates beautiful background blur (bokeh).
* Cons: Requires more distance from your subject, less versatile for other types of photography. Can be more expensive.
* 100mm/105mm: (APS-C: ~67-70mm)
* Pros: Similar to 85mm but with even more compression, great for isolating the subject, excellent background blur. Often favored for headshots.
* Cons: Requires even more distance, can feel isolating for both photographer and subject. Potentially larger and heavier.
* 135mm: (APS-C: ~90mm)
* Pros: Extreme compression, incredible bokeh, good for candid portraits from a distance.
* Cons: Requires significant distance, challenging to use in small spaces, can feel impersonal.
* 70-200mm (Zoom):
* Pros: Versatile, covers a wide range of portrait focal lengths, allows you to adjust your framing quickly without moving.
* Cons: Can be heavy and expensive, may not be as sharp as prime lenses at comparable focal lengths.
* Recommendations:
* Beginner: 50mm f/1.8 is an excellent, affordable starting point. Consider a kit lens to practice with if one came with your camera.
* Versatile: 50mm f/1.4, 35mm f/1.8 (for environmental) or 70-200mm f/2.8 (more expensive)
* Classic Portrait Look: 85mm f/1.8 or f/1.4
* Headshots: 100mm/105mm f/2.8 (often also have macro capabilities) or 85mm f/1.4
2. Aperture (f-stop):
* Why it Matters: Aperture controls the depth of field (the area in focus) and the amount of light entering the lens. Wide apertures (low f-numbers like f/1.4, f/1.8, f/2.8) create shallow depth of field, blurring the background and isolating the subject.
* Considerations:
* Wider Apertures (f/1.4 - f/2.8): Create beautiful bokeh, isolate the subject dramatically, and allow you to shoot in low light. More expensive.
* Moderate Apertures (f/4 - f/5.6): Provide a good balance between depth of field and light gathering, suitable for group portraits or when you want more of the scene in focus.
* Narrower Apertures (f/8 and above): Keep most of the scene in focus, generally not used for portraiture except for specific effects or when shooting in bright sunlight.
* Recommendations:
* Bokeh Lovers: Aim for f/1.4 or f/1.8 lenses.
* Versatility: f/2.8 lenses offer a good balance.
* Cost-Effective: f/1.8 primes are a great value. Stopping down to f/2.8 or f/4 can often yield very sharp results.
3. Image Quality (Sharpness, Contrast, Color Rendition):
* Why it Matters: A sharp lens captures fine details, while good contrast and color rendition produce lifelike and pleasing images.
* Considerations:
* Lens Reviews: Research lens reviews on reputable websites (e.g., DPReview, LensRentals, DXOMark) to assess sharpness, distortion, vignetting, and chromatic aberration (purple fringing).
* MTF Charts: These charts provide a technical assessment of a lens's sharpness across the frame.
* Sample Images: Look at sample images taken with the lens to see how it renders colors, skin tones, and overall image quality.
* Recommendations:
* Prioritize Sharpness: Especially important for headshots and detail-oriented portraits.
* Good Color Rendition: Accurate and pleasing skin tones are crucial.
* Consider Distortion: Some lenses can distort perspective, especially at wider focal lengths. Profile corrections in software can often fix this.
4. Autofocus Performance:
* Why it Matters: Fast and accurate autofocus is essential for capturing sharp portraits, especially when shooting moving subjects or in low light.
* Considerations:
* Autofocus Speed: Important for capturing fleeting moments.
* Autofocus Accuracy: Critical for tack-sharp focus on the subject's eyes.
* Autofocus System: Consider the type of autofocus system (e.g., phase detection, contrast detection, hybrid) and its compatibility with your camera.
* Motor Type: Modern lenses use ultrasonic or stepping motors for quieter and faster focusing.
* Recommendations:
* Modern Lenses: Generally have good autofocus performance.
* Test Autofocus: If possible, test the lens's autofocus performance before buying, especially in challenging lighting conditions.
5. Build Quality and Size/Weight:
* Why it Matters: A well-built lens is more durable and resistant to the elements. Size and weight affect portability and comfort during long shooting sessions.
* Considerations:
* Materials: Look for lenses with metal barrels and durable construction.
* Weather Sealing: Protects the lens from dust and moisture.
* Size and Weight: Consider your shooting style and how comfortable you are carrying a larger lens.
* Recommendations:
* Balance: Choose a lens that balances build quality with portability.
* Comfort: If you shoot for extended periods, prioritize a lighter lens.
6. Budget:
* Why it Matters: Lens prices can vary significantly, from affordable primes to high-end professional lenses.
* Considerations:
* Set a Budget: Determine how much you're willing to spend.
* Prioritize Features: Focus on the features that are most important to you.
* Consider Used Lenses: Buying used lenses can save you money.
* Recommendations:
* Start Affordable: Begin with a budget-friendly lens and upgrade later as your skills and needs evolve.
* Research Sales: Keep an eye out for deals and promotions.
7. Sensor Size (Full-Frame vs. APS-C/Crop Sensor):
* Why it Matters: Full-frame cameras have larger sensors that capture more light and produce shallower depth of field. Crop sensor cameras have smaller sensors that effectively "crop" the image, changing the field of view.
* Considerations:
* Crop Factor: APS-C cameras have a crop factor (typically 1.5x or 1.6x) that affects the effective focal length of the lens. For example, a 50mm lens on an APS-C camera will have an effective focal length of 75mm (50mm x 1.5).
* Lens Compatibility: Some lenses are designed specifically for full-frame cameras, while others are designed for crop sensor cameras. You can often use full-frame lenses on crop sensor cameras, but not the other way around (without adapters and potential limitations).
* Recommendations:
* Choose Lenses Designed for Your Sensor Size: Optimizes image quality and performance.
* Account for Crop Factor: When choosing focal lengths for APS-C cameras, factor in the crop factor to achieve the desired field of view.
8. Shooting Style and Subject:
* Why it Matters: Your shooting style and the type of portraits you want to create will influence your lens choice.
* Considerations:
* Environmental Portraits: 35mm or 50mm lenses are well-suited.
* Classic Headshots: 85mm, 100mm, or 105mm lenses are ideal.
* Candid Portraits: Longer focal lengths (135mm or 70-200mm) allow you to capture subjects from a distance.
* Studio Portraits: 85mm or 100mm lenses are commonly used.
* Outdoor Portraits: Consider the available space and lighting conditions.
In Summary:
1. Focal Length: 35mm, 50mm, 85mm, 100mm/105mm, or 70-200mm.
2. Aperture: f/1.4, f/1.8, or f/2.8 (wider apertures for shallower depth of field).
3. Image Quality: Look for sharpness, good contrast, and accurate color rendition.
4. Autofocus: Fast and accurate.
5. Build Quality: Durable and weather-sealed.
6. Budget: Set a realistic budget and prioritize features.
7. Sensor Size: Choose lenses compatible with your camera's sensor size.
8. Shooting Style: Consider the type of portraits you want to create.
The best way to find the perfect portrait lens is to experiment with different focal lengths and apertures to see what works best for you. Renting lenses before buying can be a great way to try them out without making a significant investment. Good luck!