1. Focal Length:
* 35mm:
* Pros: Excellent for environmental portraits, capturing more of the scene and telling a story. Also good for group shots and indoor portraits where space is limited.
* Cons: Can distort facial features if you get too close. Not ideal for isolating the subject.
* Use Case: Lifestyle photography, documentary portraiture, urban settings, family gatherings.
* 50mm:
* Pros: A classic, versatile choice. Offers a natural perspective, similar to human vision. Good for both headshots and wider shots. Relatively affordable, especially the f/1.8 versions.
* Cons: May not provide enough background compression for some portrait styles. Might require you to move around to frame your subject effectively.
* Use Case: Everyday portraits, general purpose, beginners looking for an affordable option.
* 85mm:
* Pros: Considered a prime portrait lens. Creates beautiful background blur (bokeh) and flattering compression of facial features. Excellent for isolating the subject and minimizing distractions.
* Cons: Can be more expensive than 50mm lenses. Requires more space to work with, potentially limiting its use in smaller studios or indoor settings.
* Use Case: Classic portraiture, headshots, minimizing background distractions, achieving a creamy bokeh.
* 100mm - 135mm:
* Pros: Excellent compression and bokeh. Allows you to maintain a comfortable distance from your subject. Great for detailed close-ups and isolating specific features.
* Cons: Can be bulky and expensive. Requires even more space to work with than 85mm lenses. May require a tripod for sharp images.
* Use Case: Professional portrait work, capturing fine details, creating a very shallow depth of field.
* 70-200mm (Zoom):
* Pros: Versatile zoom range allows you to switch between focal lengths (e.g., 85mm to 135mm) without changing lenses. Good for events where you can't easily move.
* Cons: Generally more expensive and heavier than prime lenses. Image quality might be slightly inferior to prime lenses at the same focal length and aperture.
* Use Case: Events, weddings, sports portraits, situations where versatility is key.
2. Aperture (f-stop):
* Wider Aperture (e.g., f/1.2, f/1.4, f/1.8, f/2.8):
* Pros: Creates a very shallow depth of field, blurring the background beautifully (bokeh). Allows more light to enter the lens, enabling shooting in low-light conditions and faster shutter speeds.
* Cons: More expensive. Requires precise focusing, as the depth of field is very narrow. May exhibit softer image quality at the widest apertures.
* Narrower Aperture (e.g., f/4, f/5.6, f/8):
* Pros: Greater depth of field, ensuring more of the subject is in focus. Generally sharper image quality across the frame. More forgiving when focusing.
* Cons: Less background blur. Requires more light, potentially needing a higher ISO or slower shutter speed.
3. Image Quality:
* Sharpness: How well the lens resolves details.
* Contrast: The difference between the brightest and darkest areas of the image.
* Distortion: The tendency of the lens to warp straight lines. Important for portraits, as it can affect facial features.
* Chromatic Aberration (Color Fringing): Unwanted color fringes around high-contrast edges.
* Vignetting: Darkening of the corners of the image.
4. Budget:
* Lens prices can vary greatly depending on the brand, focal length, aperture, and image quality.
* Consider starting with an affordable option (e.g., a 50mm f/1.8) and upgrading later as your skills and budget allow.
* Used lenses can be a great way to save money.
5. Your Camera System:
* Make sure the lens mount is compatible with your camera (e.g., Canon EF, Nikon F, Sony E, etc.).
* Consider whether you have a full-frame or crop sensor camera. Crop sensor cameras effectively "zoom in" on the image, so you'll need to adjust your focal length choices accordingly (e.g., a 50mm lens on a crop sensor camera will have a similar field of view to an 85mm lens on a full-frame camera).
6. Autofocus:
* Consider the autofocus speed and accuracy of the lens, especially if you're shooting portraits of moving subjects (e.g., children, pets).
* Some lenses have more advanced autofocus features, such as eye-detection AF.
7. Features:
* Image Stabilization (IS/VR): Helpful for shooting in low-light conditions or when using longer focal lengths.
* Weather Sealing: Protects the lens from dust and moisture.
* Aperture Ring: Allows you to control the aperture manually.
* Focus Limiter: Limits the range of the autofocus, speeding up focusing in certain situations.
How to Choose - A Step-by-Step Guide:
1. Define Your Style: What kind of portraits do you want to take? Environmental portraits, headshots, full-body shots? Do you prefer a lot of background blur or a more natural look?
2. Consider Your Shooting Environment: Where will you be shooting? Indoors, outdoors, in a studio? How much space will you have?
3. Set a Budget: How much are you willing to spend?
4. Read Reviews and Research: Look at sample images taken with different lenses. Read reviews from other photographers.
5. Rent or Borrow: If possible, rent or borrow a few different lenses to try them out before you buy.
6. Consider Prime vs. Zoom: Prime lenses generally offer better image quality and wider apertures, while zoom lenses offer greater versatility.
7. Prioritize Based on Your Needs: Consider what's most important to you: image quality, versatility, affordability, etc.
In summary: There is no "perfect" portrait lens for everyone. The best lens for you will depend on your individual needs and preferences. By carefully considering the factors outlined above, you can narrow down your choices and find a lens that will help you create beautiful and compelling portraits. Good luck!