The Tamron AF 24-70mm f/2.8 SP Di USD VC is quite a complex design with three low dispersion (LD) elements, two high refractive index (XR) elements, three glass molded aspheric elements and one hybrid aspheric element. In addition, the iris is 9 bladed and the blades are shaped to produce a circular aperture when the lens is stopped down for smoother out of focus areas (better “bokeh”). Clearly Tamron intend this to be a high quality lens.
While not inexpensive at a price of around $1300, the Tamron lens is nevertheless less expensive then either the Nikon 24-70/2.8 ($1800) or the new Canon 24-70/2.8L II USM ($2300). So with the lower cost and optical stabilization, the Tamron lens has a lot going for it.
Lens Construction (Groups/Elements)
Angle of View (diagonal)
84°04 -34°21 (for full frame 35mm format cameras)
60°20 -22°33 (for APS-C format cameras)
Diaphragm Blade Number
9 (rounded diaphragm)
Minimum Focus Distance
0.38m (15.0 in)
Macro Magnification Ratio
1:5 (at f=70mm: MFD 0.38m)
825g (29.1 oz)
108.5mm (4.3 in)
116.9mm (4.6 in)
88.2mm (3.5 in)
Flower-shaped Lens hood
Sony (no VC)
The Tamron 24-70/2.8 VC USD uses an Ultrasonic Drive AF motor which provides fast and silent autofocus and also allows full time manual focus, so even in AF mode the focus can be manually adjusted without having to switch from AF to MF. Stabilization (or VC – Vibration Compensation in Tamron terminology) can be manually switched on or off.
The lens is finished in the usual black matte color of Tamron lenses and has the gold “SP” stripe. There’s a wide rubberized zoom ring towards the front of the lens, with a zoom lock feature at the 24mm setting, and a narrower rubberized ring towards the back of the lens for manual focus. Ther is a distance scale, but no IR focus indication of DOF markings. Neither the focusing ring nor the filter threads rotate during autofocus. Zoom action is smooth and the lens extends by about 30mm when zoomed from 24mm to 70mm.
Tamron supply a bayonet mounting “petal” shaped hood with the 24-70/2.8 VC. The lens also comes with Tamron’s 6 year warranty.
Focus is fast and virtually silent. I measured the time to go from one focus extreme to the other at around 0.3 seconds. When mounted on an EOS 7D I could see no difference between AF and MF using live view with 10x magnification which indicates that focus was accurate. Actual images confirmed this observation.
The Tamron 24-70/2.8 VC shows significant distortion at the 24mm setting. I measured it at about -3.5% (barrel distortion) This is quite noticeable if the subject of the image fills the frame and has horizontal and/or vertical lines at the edges. However, distortion at 24mm seems to be typical of the 24-70/2.8 lenses and both the Nikon and Canon versions show visible distortion (but slightly less than the Tamron). The Tamron distortion is lower than that of the Canon EF24-105/4L.
As the lens is zoomed out distortion quickly drops. It’s hardly noticeable at 35mm and 50mm. By 70mm the character of the distortion has reversed and there is a moderate (~1%) amount of pincushion distortion.
Distortion is fairly easy to correct (or at least minimize) in post exposure processing.
As with distortion, vignetting is also most noticeable at the 24mm setting. With the lens at f2.8, the corners of the full frame image are a little over 2 stops darker than the center. Again however, this is pretty typical behavior for a 24-70/2.8 lens used wide open and both the Nikon and Canon lenses show almost as much vignetting. As the lens is stopped down the vignetting becomes less, though even at f8 there is still a little visible vignetting on a full frame image at 24mm.
Wide open vignetting is visible at all focal lengths, though it’s smaller in magnitude once the lens is zoomed out from 24mm. between 35mm and 70mm it’s around 1.5 stops at f2.8, dropping to maybe 0.5 stop by f8.
Chromatic aberration is very well controlled in the Tamron 24-70/2.8 VC. Even at the corners of the frame at 24mm CA is barely visible. On a high contrast black stripe, a measured about 1 pixel width of red on the outside and 1 pixel width of cyan on the inside. This low level of CA was pretty consistent across the focal length and aperture range.
The Tamron 24-70/2.8 has internal optical stabilization. Sensors detect lens movement and automatically moves a small group of elements in such a manner as to keep the image projected onto the sensor steady. You can see the effect quite clearly in the viewfinder. It does take a small fraction of a second for the stabilization to lock in once the shutter is 1/2 pressed, so it’s best to make sure the lens has stabilized before fully releasing the shutter.
It’s always difficult testing the effectiveness of stabilization because you’re just looking at the probability of getting a sharp shot. Stabilization doesn’t mean you’ll always have a sharp image at a slow shutter speed and the lack of stabilization doesn’t mean you’ll never get a sharp image at that same slow shutter speed.
After shooting quite a lot of test images at various shutter speeds, I came to the conclusion that the stabilization is typically worth 2-3 stops. Tamron claim 4 stops and I’ve no doubt that on occasion 4 stops can be achieved, but I wouldn’t bet on any particular shot shot at 4 stops slower than the normal lowest speed for hand-holding being sharp. Take a few shots and you’ve a better chance that one of them might be!
Unless otherwise stated, all comments relate to the Tamron 24-70/2.8VC mounted on a Canon EOS 5D full frame DSLR.
The Tamron 24-70/2.8 VC is sharp in the center at all focal lengths and apertures. At 24mm and 35mm there’s virtually no increase in resolution if the lens is stopped down. At 50 and 70mm there’s a very slight resolution improvement if the lens is stopped down a stop or two. However as far as center sharpness, resolution and contrast go, there’s no concern about shooting this lens wide open.
On a full frame image the corners are visibly less sharp than the center and at all focal lengths the corner image quality improves as the lens is stopped down. The optimum aperture for the corners is around f8. Overall, considering both center and corner sharpness, the “sweet spot” for the Tamron 24-70/2.8 VC is in the f5.6-f8 region.
Compared with the Canon 24-105/4L the Tamron 24-70/2.8 VC showed sharper corners at equal apertures. It was also sharper in the corners at 24mm than a Nikon 24-70/2.8 that I tested on a Nikon D800.
Center sharpness, as measured with the Tamron lens on an EOS 7D was very similar to that of a Nikon 24-70/2.8 mounted on a Nikon D800, which is to say very good.
Given the relatively reasonable price of the Tamron 24-70/2.8 VC and the fact that it’s the only optically stabilized lens of its type, it represents very good value. I don’t think I’d use it for wideangle landscape photography at full aperture, but that’s not really the use to which this lens is likely to be put. A 24-70/2.8 is particularly useful for events like weddings and parties, where the fast aperture can nicely blur backgrounds and it can be used indoors in relatively low light levels. For this purpose theTamron SP 24-70mm Di VC USD, (buy from Amazon) is ideal since the optical stabilization allows the use of slower shutter speeds, meaning the images can be captured at lower ISO settings.
Tamron SP 24-70mm Di VC USD, (buy from Amazon). From the Tamron website: This lens is a high-quality, highly functional, high-speed standard zoom lens covering the 24â70mm focal range. It includes both Tamronâs proprietary VC (Vibration Compensation) image stabilization to reduce shake and its USD (Ultrasonic Silent Drive) motor, enabling speedy, silent autofocusing. This SP (Super Performance) series lens makes full use of specialized glass elements in its lens layout, designed with top priority on image quality, including three LD elements and two XR (Extra Refractive Index) glasses.