Sigma 723-306 135-400mm

A tank-built 400mm zoom for Nikon F that's sharp enough but shaky without stabilization. Buy it for the reach, not the image quality.

The aperture range of f/4.5-5.6 is solidly middle of the pack, and the 135-400mm focal range gives you real reach for wildlife or airshows. The 3 ED elements and 1 aspherical element should help with chromatic aberration and edge sharpness, but the optical score lands at the 52nd percentile, so don't expect modern prime-level clarity. The lack of stabilization is a real problem at 400mm. You'll need fast shutter speeds or a tripod, especially on older Nikon bodies without IBIS. The autofocus is also just average, which on an older screw-drive or early AF lens can feel sluggish by today's standards.

Against the Tamron 28-300mm f/4-7.1 Di III VC VXD, the Sigma gives you more reach but loses stabilization and modern optical coatings. The Sony E 18-135mm f/3.5-5.6 OSS is a completely different beast, wider and stabilized, but it won't mount on Nikon F without an adapter and tops out at 135mm. The Nikon Z 17-28mm f/2.8 is sharper and faster but covers a totally different focal range. If you're on Nikon F and want 400mm on a budget, the Sigma is one of the few options at this price, but the Tamron is the smarter all-rounder if you can adapt it.

At $600 USD, this is a tough sell unless you specifically need a budget 400mm for an old Nikon DSLR or film body. The build quality is genuinely great, but you're paying for reach and durability, not optical excellence. If you can live without the 400mm end, there are sharper, stabilized options in this price range.

The Sigma 723-306 is a weird one. It's a 135-400mm f/4.5-5.6 zoom for Nikon F mount that weighs just 104g, which is frankly absurd for a lens with this reach. That weight figure is almost certainly wrong or refers to something else, because a full-frame 400mm zoom made of glass and metal cannot weigh less than a candy bar. What we can say is this is an old-school APO Aspherical design with 3 ED elements, and it's built for Nikon SLRs, not mirrorless. The build quality ranks in the 95th percentile, which tracks for Sigma's older EX-era lenses. But the optical performance sits right around average, and the macro capability is one of the worst we've seen.

If you want a sharp, stabilized all-rounder for travel or street photography, this isn't it. The macro score is abysmal, the stabilization is missing, and the optical quality is just okay. Go grab a Tamron 28-300mm VC or a used Nikon 70-300mm VR instead. You'll lose a bit of reach but gain a lot of usability.

The Sigma 723-306 is a niche lens for a specific buyer: someone with an older Nikon F-mount body who wants 400mm reach without spending four figures. The build is fantastic, but the average optics, missing stabilization, and terrible macro score make it a one-trick pony. If that trick is your trick, go for it. Otherwise, keep looking.