For aspiring documentary filmmakers, understanding the tools to enhance storytelling is as important as the story itself. One such tool is the parfocal lens—a staple in professional filmmaking known for its reliability and precision.
This guide delves into what parfocal lenses are, their benefits and drawbacks, with various budget examples. We also answer common questions to help you determine if they’re right for your projects.
Cover photo by Atharva Dharmadhikari
What Is a Parfocal Lens and How Does It Work?
A parfocal lens is a type of zoom lens designed to keep a subject in sharp focus, even as you zoom in or out. This feature eliminates the need to refocus while changing the focal length. This can save valuable time and effort, especially in fast-paced shooting environments.
The magic of parfocal lenses lies in their internal mechanics. Unlike varifocal lenses, parfocal lenses use intricate optical designs to lock the focus on your subject. This characteristic is particularly valuable when you need to change your framing mid-shot. Such as live events, interviews, or dynamic scenes.
For instance, imagine filming a speaker at a community event. You start with a wide shot to capture the stage and audience, then zoom in for a close-up of the speaker’s face. With a parfocal lens, the focus remains crisp throughout this transition. They ensure your footage looks professional and seamless.
Why Are Parfocal Lenses Useful for Documentary Work?
Parfocal lenses are especially beneficial for documentary filmmakers. This is because they allow for smooth transitions and precise focus without interruption. When working in unpredictable environments—common in documentary filmmaking—these lenses can be a lifesaver.
For example, if you’re filming wildlife, you may need to zoom in quickly to capture an animal’s movement. A parfocal lens ensures the shot stays focused, saving you the hassle of constant adjustments. Similarly, during an interview, you might want to zoom in to emphasize facial expressions or zoom out to include hand gestures. With a parfocal lens, these adjustments are effortless and visually consistent.
What Are the Drawbacks of Parfocal Lenses?
While parfocal lenses offer undeniable benefits, they also come with some drawbacks. The most notable is their cost. Due to the complex engineering required to maintain focus during zooming, parfocal lenses are more expensive than alternatives.
Another consideration is weight. Parfocal lenses often have more components and larger glass elements, making them heavier and bulkier. This can be challenging for solo filmmakers or those working with handheld setups for extended periods.
Finally, parfocal lenses are less common in the consumer market. Advancements in autofocus technology have reduced the need for true parfocal designs. Many high-end varifocal lenses now perform well enough to satisfy most filmmakers, making the distinction less critical for beginners.
How Can You Tell If a Lens Is Parfocal?
Determining whether a lens is parfocal can be tricky, especially for beginners. The simplest method is to test it yourself. Mount the lens on your camera, focus on a subject, and zoom in and out. If the subject remains sharp throughout the zoom range, the lens is parfocal.
However, be cautious of autofocus systems, as they can mask whether a lens is truly parfocal. To get accurate results, switch to manual focus during your test. Additionally, manufacturers often label their lenses as parfocal in the product description. Researching specifications can save time.
Examples of Parfocal Lenses for Different Budgets
Budget Option: Sigma 18-50mm f/2.8 DC DN
For beginners or those on a tight budget, the Sigma 18-50mm f/2.8 DC DN offers a great starting point. While it’s not a true parfocal lens, its optical design provides performance close enough to meet the needs of many documentary projects.
This compact and lightweight lens is ideal for run-and-gun shooting, making it a versatile option for filmmakers on the go. Priced around $500, it’s an affordable choice for those looking to experiment with parfocal-like capabilities.
Mid-Range Option: Sony 24-70mm f/2.8 GM
Moving up the scale, the Sony 24-70mm f/2.8 GM is a workhorse lens for professionals who demand quality without overspending.
Known for its sharpness and reliability, it delivers excellent results. This is across various documentary and dynamic scenarios. Whether they are interviews or action shots. While heavier than budget lenses, its durability and performance justify the $2,000 price tag.
High-End Option: Canon CN-E 30-300mm T2.95-3.7 L SP
For those working on high-budget productions, the Canon CN-E 30-300mm T2.95-3.7 L SP is the ultimate choice. As a true parfocal lens, it offers incredible zoom range and impeccable image quality. It is ideal for cinematic documentaries.
With a price exceeding $40,000, this lens is primarily reserved for large-scale projects with substantial budgets.
FAQs About Parfocal Lenses
Are Parfocal Lenses Better for Video?
Yes, especially for video work where zooming mid-shot is common. Parfocal lenses maintain sharp focus throughout the zoom range. They allow for smooth transitions that enhance the professional quality of your footage. In documentary filmmaking, you may not have the chance of reshooting scenes. The reliability of a parfocal lens can make a significant difference.
What’s the Difference Between Parfocal and Varifocal Lenses?
The key distinction lies in focus. Parfocal lenses maintain focus when zooming. Varifocal lenses need refocusing after changing the focal length. For example, if you’re filming a subject and zoom in with a parfocal lens, the image stays sharp. With a varifocal lens, you’ll need to pause and adjust focus manually or rely on autofocus to compensate.
Do I Need a Parfocal Lens for Documentary Work?
It depends on your style and budget. If your projects involve a lot of dynamic zooming—such as wildlife, live events, or handheld interviews—a parfocal lens can save time and ensure your footage remains consistent. However, if your budget is limited, modern varifocal lenses with advanced autofocus systems can achieve similar results in many scenarios.
Can I Achieve Parfocal-Like Results with a Varifocal Lens?
Yes, by leveraging your camera’s autofocus capabilities or carefully refocusing after each zoom. While it isn’t as seamless as a true parfocal lens, many filmmakers achieve professional results with high-quality varifocal lenses. Practice and familiarity with your gear are key to maximizing performance.
Why Are Parfocal Lenses So Expensive?
The engineering required to maintain focus across the entire zoom range is complex. This involves precise optical alignment and additional components, which increase manufacturing costs. Parfocal lenses are also geared toward professional markets, where performance is prioritized over affordability.
Final Words: Are Parfocal Lenses Worth It?
Parfocal lenses are a powerful tool for documentary filmmakers. They offer precision and flexibility that can elevate your storytelling. While their cost and weight may be prohibitive for some, the ability to maintain focus during zooming can save time. It can also enhance your creative freedom.
Whether you’re just starting or producing high-budget films, there’s a parfocal lens to suit your needs. As you explore your options, remember that storytelling always comes first. Choose the tools that best align with your vision and workflow.
