1. Understanding the Basics:
* Focal Length: The most important factor. Focal length affects perspective, compression, and how much background blur you get.
* Aperture (f-stop): Determines the depth of field (how much of the image is in focus) and the lens's ability to gather light. A wider aperture (lower f-number like f/1.4, f/1.8, f/2.8) creates shallower depth of field, beautiful background blur (bokeh), and performs better in low light.
* Image Quality: Sharpness, contrast, color rendering, distortion, and vignetting are all crucial for portraits.
* Autofocus (AF) Speed and Accuracy: Fast and accurate autofocus is essential, especially when shooting portraits of moving subjects or using shallow depth of field.
* Build Quality: A robust and weather-sealed lens is more durable and can withstand various shooting conditions.
* Price: Lens prices vary drastically. Set a budget and stick to it.
2. Focal Length Considerations:
* 35mm:
* Pros: Wide enough to capture the environment, good for environmental portraits (telling a story about the subject's surroundings). More forgiving of movement.
* Cons: Can distort facial features if you get too close. Not as much background blur as longer lenses. Requires you to be closer to the subject.
* Good For: Candid portraits, environmental portraits, street photography with a subject focus.
* 50mm:
* Pros: Versatile "standard" focal length, relatively inexpensive (especially the f/1.8 versions), good for both full-body and head-and-shoulder portraits, natural perspective.
* Cons: May not provide enough background blur for some. Still requires you to be relatively close to the subject.
* Good For: A great starting point for portrait photography, all-around use.
* 85mm:
* Pros: A classic portrait focal length, flattering perspective (minimizes distortion), excellent background blur (bokeh), ideal for headshots and upper-body portraits. Allows you to be further from the subject for a more relaxed feel.
* Cons: Can be a bit tight for full-body shots in small spaces. More expensive than 50mm lenses.
* Good For: Headshots, upper-body portraits, isolating the subject, creamy background blur.
* 100mm - 135mm:
* Pros: Even more compression than 85mm, excellent for isolating the subject, beautiful bokeh, flattering perspective. Comfortable working distance.
* Cons: Can be expensive and bulky, requires more space to work, potentially slower autofocus on some models.
* Good For: Similar to 85mm but with even more reach, detailed close-ups. Great for outdoor portraits where you have space.
* 70-200mm Zoom Lenses:
* Pros: Versatile zoom range, allows you to quickly adjust focal length, often have image stabilization, can be used for other types of photography.
* Cons: Typically more expensive and heavier than prime lenses, maximum aperture is often smaller (e.g., f/2.8 or f/4), may not be as sharp as prime lenses at their widest aperture.
* Good For: Events, weddings, situations where you need flexibility, outdoor portraits.
* Longer Focal Lengths (200mm+):
* Pros: Extreme compression, very shallow depth of field (for maximum background blur), allow you to photograph subjects from a significant distance (e.g., wildlife, candid shots).
* Cons: Very heavy and expensive, require a lot of space to work, require a very steady hand or tripod.
* Good For: Candid portraits from a distance, isolating small details, wildlife portraits.
3. Aperture Considerations:
* f/1.2 - f/1.8: Excellent for very shallow depth of field, creating creamy bokeh, and shooting in low light. More expensive and require very precise focusing.
* f/2 - f/2.8: Still provides good background blur, easier to achieve focus, often sharper than wider apertures, and less expensive.
* f/4 - f/5.6: Greater depth of field, useful for environmental portraits or group shots where you want more of the scene in focus. More forgiving of focus errors.
* f/8 and smaller: Maximum depth of field, used when you want almost everything in focus.
4. Camera Sensor Size (Crop Factor):
* Full Frame: The listed focal lengths are what you get.
* APS-C (Crop Sensor): You need to multiply the focal length by the crop factor (typically 1.5x or 1.6x). So, a 50mm lens on an APS-C camera behaves like a 75mm or 80mm lens on a full-frame camera. This means you need a shorter lens to get the same field of view. A 35mm lens is a great starting point for APS-C.
5. Budget Considerations:
* Entry-Level: A "nifty fifty" (50mm f/1.8) is an excellent and affordable starting point for any system. Consider a 35mm f/2 or f/1.8 for APS-C.
* Mid-Range: An 85mm f/1.8 or f/2 lens offers excellent image quality and beautiful bokeh without breaking the bank.
* High-End: An 85mm f/1.4, 70-200mm f/2.8, or specialized portrait lenses offer the ultimate in image quality, build, and features.
6. Lens Features to Consider:
* Image Stabilization (IS/VR): Helpful for handheld shooting, especially in low light or with longer focal lengths.
* Weather Sealing: Protects the lens from dust and moisture.
* Focus Motor Type: Ultrasonic motors (USM, HSM, etc.) are generally faster and quieter than traditional motors.
* Minimum Focusing Distance: Important if you want to take close-up portraits.
7. Trying Before You Buy:
* Rent lenses: This is the best way to test out different focal lengths and apertures before investing in a lens. Services like LensRentals.com or BorrowLenses.com are great options.
* Visit a camera store: Handle the lenses, try them out on your camera, and see how they feel.
* Borrow from a friend: If you have friends with different lenses, ask if you can borrow them for a test shoot.
8. Your Personal Style:
* Think about the type of portraits you want to create: Do you prefer tight headshots, full-body portraits, environmental portraits, or something else?
* Consider your shooting environment: Will you be shooting mostly indoors, outdoors, in a studio, or on location?
* Evaluate your existing equipment: Do you need a lens that complements your current lenses, or are you starting from scratch?
Example Scenarios and Lens Recommendations:
* Budget-conscious beginner (Full-frame): 50mm f/1.8
* Budget-conscious beginner (APS-C): 35mm f/1.8
* Professional portrait photographer: 85mm f/1.4 or 70-200mm f/2.8
* Wedding photographer: 24-70mm f/2.8 and 70-200mm f/2.8
* Environmental portraits: 35mm f/1.4 or 50mm f/1.4
* Studio headshots: 85mm f/1.8 or 100mm f/2.8 macro (also great for detail)
In summary, there is no "perfect" portrait lens for everyone. The best lens for you will depend on your budget, shooting style, camera system, and personal preferences. Experiment, try different lenses, and find what works best for you and the kind of portraits you want to create.