While we were at CP+ 2015 in Japan, we met with Tamron, and the company was kind enough to lend us their newly announced 15-30mm F2.8 Di VC USD. In Nikon mount, no less. Why the big deal about it being Nikon mount? Because that means we can attach it natively to the Nikon D810 - the highest-resolution DSLR currently on the market (until the Canon EOS 5DS and 5DSR show up in June). 

15-30mm is a wide range for a full-frame zoom, made more impressive by the inclusion of vibration compensation (VC). The wide F2.8 aperture and inclusion of VC do mean the lens is rather heavy and bulky, weighing 1100g, 100g heavier - and physically wider throughout the lens barrel - than the Nikon 14-24 F2.8, as you can see below. 

Front View	Side View

Both the Tamron 15-30mm F2.8 VC and Nikon 14-24mm F2.8 wide angle zooms have large, bulbous front elements that make attaching filters difficult, if not impossible. Although an option does exist for the Nikon 14-24, it requires rather large (not to mention expensive) 150mm wide filters. No such filter option exists (yet) for the Tamron, and neither lens offers support for rear-mounted gelatin filters.  

With a price tag of $1200, Tamron is taking the Nikon 14-24 head-on, and so we decided to do the same: pit the two against one another in a shootout. 

We shot a distant scene by mounting both lenses on the 36MP Nikon D810, focusing (in Live View) on the roof of the building just in front of the yellow crane near the center of the image. We shot Raw, and normalized the brightness across all images in ACR. We left sharpening and noise reduction at default, and applied no vignetting, chromatic aberration, or distortion corrections.

At F2.8, the Tamron edges out the Nikon a little in center sharpness, outperforms it significantly in left corner sharpness, and is of comparable sharpness at the right corner. Note that at slightly less extremes, the differences are hardly worth noting, with the Nikon even perhaps slightly outperforming the Tamron in the left and right less extreme corners. By the way, we have a suspicion the Tamron may be a tiny bit decentered, and that a better copy would've yielded even better performance for the Tamron on the right side of the frame.

By F5.6 the lenses perform very similarly in the left and right corners, while center sharpness goes to the Tamron, but for a subtle reason. We picked a focus method that yielded maximum sharpness across the field which, for the Nikon, meant a slight center sharpness cost (the Tamron showed no such tradeoff). Once we focused the Nikon using the center point at the shooting aperture, we got better center sharpness that matched the Tamron's, but at the cost of softer corners. In other words, with our copy of the Nikon, we couldn't optimize for both center and corner sharpness. For a more in-depth look at this behavior, visit our deeper dive on page 3.

The Tamron continues to outperform the Nikon wide open at even longer focal lengths, though the pattern of the lenses being largely indistinguishable by F5.6 holds. Play with the widget and have a look yourself, but suffice it to say: we're impressed.

Sharpness isn't the entire story though... read about how this lens performs with respect to other optical considerations - like how wide it gets compared to the Nikon - on page 2.