When diving into the world of third-party lenses for Sony cameras, especially for filmmakers using bodies like the FX30, understanding the nuances of lens performance is crucial. Today, we’re focusing on comparing Sigma lenses, specifically the popular Sigma 18-50mm f/2.8 DC DN Contemporary, against a strong competitor, the Tamron 17-70mm f/2.8 Di III-A VC RXD, in terms of focus breathing and image stabilization. These factors can significantly impact the quality and usability of your footage, especially when shooting video.
Focus Breathing: Sigma 18-50mm vs. Tamron 17-70mm
Focus breathing, the subtle change in a lens’s field of view as focus is adjusted from near to far, is a common consideration for videographers. Neither the Sigma nor the Tamron lens benefits from Sony’s in-camera lens breathing compensation, being third-party options. Examining the Sigma 18-50mm f/2.8, focus breathing is present but relatively minimal. At the wider 18mm end, it’s barely noticeable. Stepping up to 50mm, a slight shift in the frame becomes apparent as focus changes, but it remains within acceptable limits for most shooting scenarios.
The Tamron 17-70mm f/2.8 presents a similar profile in terms of focus breathing. At its 17mm widest angle, focus breathing is minimal to non-existent. However, as you zoom towards 70mm, the frame shift becomes more noticeable during focus adjustments. While both lenses exhibit focus breathing, in practical use, it’s unlikely to be a major distraction. For lenses in this price range, particularly third-party options, the levels of focus breathing are quite manageable and often go unnoticed, especially in fast-paced shooting.
Image Stabilization: A Tale of Two Approaches
Image stabilization is where the comparison takes an interesting turn. The Tamron 17-70mm f/2.8 comes equipped with built-in Vibration Compensation (VC), Tamron’s image stabilization technology. In contrast, the Sigma 18-50mm f/2.8 does not include optical stabilization. However, the performance on Sony cameras, specifically the FX30, introduces a layer of complexity.
Using the Tamron 17-70mm f/2.8 with the Sony FX30, some users have reported unusual frame jumps, particularly when using manual focus and internal stabilization simultaneously. This behavior has been observed with Tamron lenses that feature internal stabilization on Sony bodies. Consequently, while using the Tamron on the FX30, it’s often recommended to stick to standard stabilization mode and avoid active stabilization to prevent these frame jumps. On a tripod, stabilization should ideally be turned off entirely.
The Sigma 18-50mm f/2.8, lacking internal stabilization, circumvents this issue. With the Sigma lens, you can confidently leave the active stabilization mode engaged on cameras like the FX30 at all times. This can be advantageous for handheld shooting, as active stabilization offers enhanced steadiness. However, it’s important to note that for dynamic movement shots with either lens, especially while walking, a gimbal is highly recommended to achieve truly smooth and professional-looking footage.
Conclusion: Choosing Between Sigma and Tamron
Both the Sigma 18-50mm f/2.8 and the Tamron 17-70mm f/2.8 offer compelling features for filmmakers and photographers seeking versatile zoom lenses for Sony APS-C cameras.
If maximum sharpness and a wider zoom range are top priorities, the Tamron 17-70mm f/2.8 generally holds an edge, delivering slightly superior image quality, particularly at the wider end. However, this comes with the caveat of potentially needing to adjust stabilization settings on cameras like the Sony FX30 to avoid frame jumping issues.
Conversely, if a more compact and lightweight setup is desired, and seamless compatibility with Sony’s active stabilization is important, the Sigma 18-50mm f/2.8 is an excellent choice. While it may exhibit slightly more distortion and be a touch less sharp at the wider end compared to the Tamron, its smaller form factor and reliable stabilization performance make it a very attractive option, especially for run-and-gun shooting. The Sigma lens’s focus ring being flush with the lens body might be a minor ergonomic consideration for some users.
Ultimately, the “better” lens depends on individual needs and shooting preferences. For users prioritizing image quality and zoom versatility, the Tamron 17-70mm f/2.8 is a worthwhile investment. For those favoring portability and streamlined stabilization with active mode on Sony cameras, the Sigma 18-50mm f/2.8 stands out as a highly capable and cost-effective lens. Considering the slight price difference, the Tamron 17-70mm f/2.8 often justifies its higher cost with its enhanced image quality and extended zoom range.
