1. Understanding Key Concepts
* Focal Length: This is the distance (in millimeters) between the lens and the image sensor when the lens is focused at infinity. It affects the perspective and magnification.
* Aperture (f-stop): This controls the amount of light entering the lens. A wider aperture (smaller f-number like f/1.8) lets in more light, creates a shallower depth of field, and blurs the background.
* Depth of Field (DOF): The area of the image that appears acceptably sharp. A shallow DOF isolates the subject, while a deep DOF keeps more of the scene in focus.
* Compression: Longer focal lengths compress the background, making it appear closer to the subject. Shorter focal lengths expand the perspective.
* Distortion: Certain lenses can introduce distortion. Wide-angle lenses often have barrel distortion (straight lines bowing outwards), while some telephoto lenses can have pincushion distortion (straight lines bowing inwards).
2. Ideal Focal Lengths for Portraits
The "classic" portrait range is generally considered to be 50mm to 135mm (full-frame equivalent). Let's break down some common choices:
* 50mm (The Versatile Option):
* *Pros:* Relatively inexpensive, lightweight, close to human perspective, good in various situations, often has a wide aperture (e.g., f/1.8).
* *Cons:* Can sometimes feel a bit wide for close-up portraits, requires you to get closer to your subject.
* *Best For:* Environmental portraits (showing the subject in their surroundings), candid shots, when space is limited. Good for beginners.
* 85mm (The Portrait Staple):
* *Pros:* Excellent subject isolation, flattering perspective, good compression, generally sharp, beautiful bokeh (background blur).
* *Cons:* Can be more expensive than 50mm, requires more space.
* *Best For:* Classic headshots, shoulder-up portraits, portraits where you want to blur the background significantly. This is often considered the *ideal* portrait focal length by many.
* 100mm - 135mm (Tight Shots and Compression):
* *Pros:* More background compression than 85mm, very flattering perspective, good for tight headshots, allows you to maintain distance from the subject.
* *Cons:* Requires even more space, can feel isolating if you're too far from your subject, potentially more expensive.
* *Best For:* Headshots, beauty shots, portraits where you want a very blurred background and compressed perspective.
* 70-200mm Zoom (Versatility in a Zoom):
* *Pros:* Very versatile, covers a wide range of portrait focal lengths, allows you to zoom in and out without moving, great for candid shots and events.
* *Cons:* Can be heavy and expensive, may not have as wide of an aperture as prime lenses. The image quality often isn't *quite* as good as a comparable prime lens at the same focal length.
* *Best For:* Events, weddings, situations where you need flexibility in focal length, photographing moving subjects.
* Wider than 50mm (Environmental, Creative):
* *Pros:* Captures more of the environment, creates a more dynamic perspective, good for storytelling.
* *Cons:* Can distort facial features if used too close, may not be as flattering for traditional portraits.
* *Best For:* Environmental portraits, editorial portraits, creative shots where you want to include the surroundings. Requires careful composition to avoid distortion.
Important Notes Regarding Crop Sensors (APS-C, Micro Four Thirds):
If you have a crop-sensor camera (APS-C or Micro Four Thirds), you need to consider the crop factor. This will change the effective focal length of the lens. To find the equivalent focal length, multiply the lens's focal length by the crop factor:
* APS-C (Canon): Crop factor is 1.6x (e.g., a 50mm lens acts like an 80mm lens)
* APS-C (Nikon, Sony, Fuji): Crop factor is 1.5x (e.g., a 50mm lens acts like a 75mm lens)
* Micro Four Thirds: Crop factor is 2x (e.g., a 25mm lens acts like a 50mm lens)
Example for Crop Sensors: If you want an 85mm equivalent on an APS-C (1.5x crop), you'd need a lens around 56mm (85 / 1.5 = 56.66). A 50mm lens would be a close, and common, alternative.
3. Aperture Considerations
* Wide Apertures (f/1.2 - f/2.8):
* *Pros:* Shallow depth of field, excellent subject isolation, beautiful bokeh, great in low light.
* *Cons:* Can be expensive, more difficult to nail focus precisely (especially at wider apertures), may have softer corners.
* Moderate Apertures (f/2.8 - f/4):
* *Pros:* Good balance between shallow depth of field and sharpness, easier to focus, often more affordable.
* *Cons:* Background blur may not be as pronounced as with wider apertures.
* Smaller Apertures (f/5.6 and beyond):
* *Pros:* Greater depth of field, useful for group portraits or environmental portraits where you want more in focus, less expensive.
* *Cons:* Less subject isolation, not ideal for low-light situations.
4. Other Important Factors
* Build Quality: A well-built lens will last longer and be more durable. Consider the materials used (metal vs. plastic) and the overall construction.
* Autofocus: Fast and accurate autofocus is crucial, especially for photographing moving subjects. Look for lenses with good autofocus systems. Consider if you need image stabilization (IS/VR/OS) to help with handheld shooting, especially in low light.
* Image Stabilization (IS/VR/OS): Helps reduce camera shake, allowing you to shoot at slower shutter speeds. This is very helpful in low light or when using longer focal lengths.
* Lens Aberrations: Look for reviews that discuss chromatic aberration (color fringing), vignetting (darkening of the corners), and distortion.
* Bokeh Quality: The quality of the background blur is important. Look for lenses that produce smooth, creamy bokeh. Sample images are your friend here.
* Budget: Lenses can range from a few hundred dollars to several thousand. Determine your budget and find the best lens within your price range.
* Used vs. New: Consider buying a used lens to save money. Check its condition carefully before purchasing.
* Lens Reviews: Read reviews from reputable sources (e.g., DPReview, LensRentals, Ken Rockwell) to get an idea of a lens's performance.
5. Trial and Error is Key
* Rent Lenses: Before buying a lens, rent it for a few days to see if you like it. LensRentals.com and BorrowLenses.com are popular options.
* Borrow from Friends: If you have friends who own different lenses, ask if you can borrow them to try them out.
* Test in a Store: Visit a camera store and try out different lenses on your camera.
6. Summary of Recommendations (General Guide):
* Beginner: 50mm f/1.8 (affordable, versatile, good learning lens)
* Classic Portraits: 85mm f/1.8 or f/1.4 (excellent subject isolation and bokeh)
* Versatile Zoom: 70-200mm f/2.8 (covers a wide range of focal lengths)
* Tight Headshots: 100mm or 135mm (great compression)
* Environmental Portraits: 35mm or 50mm (includes more of the surroundings)
* Budget Option: Used lenses can often offer excellent value.
7. Ask Yourself These Questions:
* What is my budget?
* What type of portraits do I shoot most often (headshots, full body, environmental)?
* What kind of look do I want to achieve (shallow depth of field, compressed perspective)?
* What are the lighting conditions I typically shoot in?
* Do I need a zoom or is a prime lens sufficient?
* Do I have a crop sensor or full-frame camera?
By carefully considering these factors and doing your research, you can find the perfect portrait lens to capture stunning images of your subjects. Good luck!