1. Focal Length:
* 35mm: (Not strictly a "portrait" lens, but popular for environmental portraits)
* Pros: Wide field of view, good for capturing the subject in their surroundings, allows for storytelling.
* Cons: Can distort facial features if you get too close, not ideal for tight headshots. You need to be close to your subject, which can make some people uncomfortable.
* Best for: Environmental portraits, showing context, documentary-style portraits, candid shots.
* 50mm: (The "nifty fifty" and a very versatile choice)
* Pros: Relatively inexpensive, lightweight, good for full-body and half-body portraits, minimal distortion, more separation than wider lenses.
* Cons: May require cropping for headshots, might need more space for full-body shots.
* Best for: General purpose portraits, both indoor and outdoor, all body types. A great starting point.
* 85mm: (A classic portrait lens)
* Pros: Excellent subject isolation, flattering compression (reduces distortion and makes features appear more balanced), pleasing bokeh, good for headshots and upper body shots.
* Cons: Requires more distance from the subject, can feel limiting in tight spaces, more expensive than 50mm.
* Best for: Headshots, upper body shots, creating a soft and dreamy background, professional-looking results.
* 100mm - 135mm: (Telephoto portrait lenses)
* Pros: Stronger compression for more flattering results, beautiful bokeh, excellent for isolating the subject.
* Cons: Requires even more distance, can be challenging in small studios, more expensive and often heavier.
* Best for: Outdoor portraits, situations where you need distance, isolating your subject against busy backgrounds. Great for close-ups without having to get in the person's face.
* 70-200mm Zoom: (A very versatile option if you want multiple focal lengths)
* Pros: Flexible focal length range, can be used for a variety of portrait styles, good image quality in the high-end versions.
* Cons: Typically more expensive, heavier and bulkier than prime lenses, may not be as sharp as a dedicated prime.
* Best for: Weddings, events, situations where you need to quickly change focal lengths, capturing candid moments from a distance.
2. Aperture (f-stop):
* Wider Aperture (e.g., f/1.4, f/1.8, f/2.8):
* Pros: Creates shallow depth of field for blurry backgrounds (bokeh), allows more light in for low-light shooting, isolates the subject effectively.
* Cons: Shallower depth of field requires more precise focusing, expensive to manufacture.
* Narrower Aperture (e.g., f/4, f/5.6, f/8):
* Pros: Greater depth of field, more of the image is in focus, easier to achieve sharp focus, less expensive lenses.
* Cons: Less background blur, requires more light.
General Rule: A wider aperture is generally preferred for portraiture to create a shallow depth of field and isolate the subject. However, consider how much of your subject you want in focus. For group portraits, a narrower aperture will be necessary to ensure everyone is sharp.
3. Image Quality:
* Sharpness: Look for a lens that delivers sharp images, especially in the center of the frame. Read reviews and compare test shots.
* Contrast: The lens should produce good contrast, giving your images a sense of depth.
* Color Rendition: The lens should render colors accurately and pleasingly.
* Distortion: Minimize distortion, especially with wider lenses, to avoid unnatural-looking portraits. 85mm and longer typically have very little distortion.
* Aberrations: Chromatic aberration (color fringing) and other aberrations can degrade image quality. Look for lenses with good aberration control.
4. Autofocus Performance:
* Speed and Accuracy: A fast and accurate autofocus system is crucial for capturing sharp portraits, especially with moving subjects.
* Quietness: A quiet autofocus motor is beneficial, particularly for video recording.
* Eye Autofocus: Many modern cameras offer eye autofocus, which can significantly improve the accuracy of your portrait shots. Choose a lens that works well with your camera's autofocus system.
5. Build Quality and Durability:
* Robust Construction: A well-built lens will withstand the rigors of regular use.
* Weather Sealing: If you shoot outdoors, weather sealing can protect your lens from dust and moisture.
* Ergonomics: Consider how the lens feels in your hand and how easy it is to operate.
6. Budget:
* Portrait lenses range in price from a few hundred dollars to several thousand. Determine your budget and look for the best lens you can afford within that range.
* Consider buying used lenses to save money.
7. Crop Sensor vs. Full Frame:
* Crop Factor: If you're shooting with a crop sensor camera (APS-C), you need to account for the crop factor (typically 1.5x or 1.6x). A 50mm lens on a crop sensor camera will have a field of view equivalent to a 75mm or 80mm lens on a full frame camera.
* Dedicated Crop Sensor Lenses: Some manufacturers offer lenses specifically designed for crop sensor cameras. These lenses may be smaller, lighter, and less expensive than full frame lenses.
8. Consider your Subject:
* Adults vs. Children: Working with children often requires a faster autofocus and sometimes a bit of distance (telephoto lens) to not intrude on their space.
* Individuals vs. Groups: Groups need a wider aperture to get everyone in focus.
* Location: Indoor vs. Outdoor. Outdoor locations often allow for longer focal lengths.
9. Rent Before You Buy:
* The best way to find the perfect portrait lens is to try out a few different options. Rent lenses from a local camera store or online rental service. This will allow you to experiment with different focal lengths and apertures and see which one best suits your needs.
In summary, here's a suggested decision-making process:
1. Budget: How much are you willing to spend?
2. Camera Type: Crop sensor or full frame?
3. Shooting Style: Environmental portraits, headshots, full-body shots, candid shots?
4. Location: Indoor, outdoor, or both?
5. Aperture Requirements: How shallow a depth of field do you want?
6. Autofocus Needs: How fast and accurate does your autofocus need to be?
7. Rental/Testing: Rent or borrow different lenses to try them out.
By carefully considering these factors, you can choose the perfect portrait lens that will help you capture stunning and memorable images.