600mm f/4 or 400mm f/2.8? Lens buying thoughts from a wildlife photographer

Product Comparison: 600mm f/4 vs. 400mm f/2.8

Steve has used Nikon 600mm f/4 lenses for about 10 years. He recently tested and bought a Sony 400mm f/2.8, considering whether its wider focal length and faster aperture better suit his wildlife photography.

Sony 400mm f/2.8: Features and Experience

• Wide and fast: At 400mm and f/2.8, the lens captures more of the surroundings, creates strong background separation, and allows twice the shutter speed of an f/4 lens in otherwise similar conditions.
• With a 1.4× teleconverter: The lens becomes a 560mm f/4. Steve found image quality excellent even wide open, with excellent autofocus speed and accuracy on the Sony A1. For his needs, 560mm is close enough to 600mm f/4.
• With a 2× teleconverter: The lens reaches 800mm f/5.6. The results are usable, but Steve prefers stopping down by a stop for sharpness. Image quality is not as strong as with the bare lens or the 1.4× combination.
• Steve found Sony’s teleconverters worked much better for him than Nikon’s, which he had used reluctantly.
• He borrowed a friend’s lens for a week in the Tetons before buying it, then continued using the combination for roughly six to eight weeks.

Advantages and Drawbacks Compared with 600mm f/4

Why the 400mm f/2.8 Suits Steve

• It performs better for low-light wildlife, including owls in dark forests.
• Its 400mm focal length is useful for large mammals such as bears, elk, moose, and bison.
• It offers more flexibility to shoot wider and include the environment.
• Teleconverters provide useful longer-reach options at 560mm and 800mm.

Why the 600mm f/4 May Suit Others Better

• Its longer native reach is valuable for small birds and dedicated bird photography.
• With a 2× teleconverter, it can reach 1200mm—beyond the reach of the 400mm setup.
• Steve’s concerns about image quality and autofocus with a teleconverter were resolved through testing, though the 2× converter remains a compromise.

Buying Advice and Verdict

The lenses were cited as costing about $12,000 and $13,000 new; Steve bought the 400mm used. The price difference—under 10%—was not a deciding factor for him. The intended use mattered more. He recommends renting or borrowing either lens, or both, before committing to such an expensive purchase.

Verdict: Steve’s early experience suggests the 400mm f/2.8 is the better fit for his mix of large mammals, low-light subjects, and wider environmental compositions. He plans to use it as his primary big prime while keeping both lenses until he can also test a Nikon Z9. The 600mm f/4 remains the stronger choice for photographers who prioritize maximum reach, especially dedicated bird photographers.

Speakers

• Steve Matthies: Provides the review and personal comparison.
• Joel: Not heard in the subtitles. Steve says Joel lent him the 400mm f/2.8 for a week and owns both lenses.