🔍 Optical Design at a Glance

The lens structure is built around three key groups:

• G₁ (Front Group): A fixed positive-power group split into two subgroups with a strategic air gap, helping reduce size and weight while correcting aberrations.
• G₂ (Internal Focusing Unit): A lightweight movable group that delivers quick, quiet autofocus ideal for both stills and video.
• G₃ (Rear Group): Includes the image stabilization unit and rear optics. A smart optical power balance improves stabilization while keeping the system compact.

The result is a lightweight, stabilized telephoto zoom that can go from 250mm to 500mm with minimal compromise.

🎯 Who Is It For?

This lens is ideal for:

• Wildlife photographers who need handheld reach in remote areas
• Sports shooters looking to cover distant action without lugging giant primes
• Documentary and nature filmmakers using mirrorless cameras in the field

The internal focusing and stabilized optics make it especially compelling for hybrid shooters working in both video and stills.

🔧 Engineering Highlights

• Optimized spacing and lens power ratios reduce weight without sacrificing image quality
• All spherical lens elements keep manufacturing consistent and cost-effective
• Rear IS unit enables effective shake correction with minimal optical disturbance
• Designed to resolve high-res sensors up to 500mm with solid corner sharpness

📌 Final Thoughts

Sigma’s 250–500mm f/6 could mark the arrival of a new class of portable super-telephoto zooms: long-reach, pro-level optics in a mirrorless-friendly body. If and when it hits the market, this lens could become a go-to choice for those who want the reach—without the bulk.