Tamron SP 24-70mm f/2.8 Di VC USD review – Introduction

A popular lens choice for full-frame camera users is the 24-70mm f/2.8 optic, because its range covers general use and the fast aperture is constant throughout the entire focal range. Indeed, most camera retailers recommend it as the lens to buy with a full-frame camera as part of a kit. We usually identify third-party lenses as more affordable alternatives to brand-name optics, and any such products stir up a lot of interest. In the case of the Sigma 24-70mm f/2.8 EX DG HSM lens, for example, it is at least half the price of some proprietary models at around £600. Somewhat surprisingly, though, this is not the case with the Tamron SP 24-70mm f/2.8 Di VC USD.

Available in Canon, Nikon and Sony mounts, with the Canon version tested here, the Tamron SP 24-70mm f/2.8 Di VC USD costs around £1,000 (street price). Equivalent brand-name lenses are priced around £1,200 for Nikon, £1,000 for the Canon (Mark I), £2,300 for the new Canon Mark II and £1,450 for the Sony Carl Zeiss. While the Tamron optic is less expensive, it is not significantly so. On that basis, we would expect the optical quality and handling of the Tamron lens to be first rate.

Features

Image: The 17 elements in 12 groups includes three LD (yellow), three aspherical (red), one hybrid aspherical (orange) and two extra refractive elements (green) 

As with most lenses these days, there are several letters used to describe the Tamron 24-70mm optic, each of which denotes a feature. SP (Super Performance) indicates that the lens is from Tamron’s professional range.

Indeed, the optical construction is impressive, comprising 17 elements in 12 groups and including three LD (low dispersion) elements, three glass-moulded aspherical elements, one hybrid aspherical element and two XR (extra refractive index) elements. The nine diaphragm blades are rounded to give a pleasing circular shape to out-of-focus areas (bokeh).

Di shows that the lens is fully compatible with both full-frame and APS-C-format cameras (giving the latter a 35mm equivalent focal range of 36-105mm). However, the optic is really targeted at
full-frame users.

VC denotes Vibration Compensation, which is a unique selling point for this lens among its competitors. Offering image stabilisation is an advantage because it enables the use of slower shutter speeds of anything up to 5EV while maintaining shake-free results. Tamron does not specify how much extra shake-protection VC gives, but I found it to be up to 4EV while testing the lens. The inclusion of image stabilisation is no doubt a factor that adds to the price of the lens.

Finally, USD stands for Ultrasonic Silent Drive, a motor that provides fast and quiet autofocus.

Build and handling

At 825g, the Tamron lens is reassuringly weighty. This is not only due to the amount of glass packed into the lens, but also the inclusion of Vibration Compensation. However, because Sony includes image stabilisation in its camera bodies, Vibration Compensation is not included in the Sony-fit version of this lens. Although the Tamron lens is a similar length to other 24-70mm f/2.8 models, it is a little chunkier at 88.2mm in diameter and with an 82mm lens thread. The size and weight of the lens balance well with a camera like the Canon EOS 5D Mark III that was used in this test.

The lens body is built to a high standard, with a moisture-resistant and weather-sealed, high-quality plastic construction and, as one would expect, a metal lens mount with appropriate contacts for full auto control. I have used all the brand-name versions of this lens, and can say that this Tamron model features extra controls, including a switch to activate Vibration Compensation. A lock for the zoom is also included, which can be used at the 24mm setting when the lens is packed away to prevent the barrel from extending.

It took me some time to become acclimatised to the placement of the focus and zoom rings. Unusually, the focus ring is closer to the camera body with the zoom control at the far end. When focusing manually, I often had to search for the focus ring, so I would like to see it a little wider for a quicker find. However, both the zoom and focus rings are dampened for smooth control. Close focus is quoted at 38cm.

Optical quality

See large version of this resolution chart

The Canon lens has a slight edge over the Tamron optic at its widest aperture and at its sharpest f/5.6 aperture. However, the differences are minimal and both lenses are impressive.

We shot our resolution charts using the Canon EOS 5D Mark III, with both the Tamron lens and the similarly priced Canon 24-70mm f/2.8L USM, at 24mm, 50mm and 70mm settings. The charts indicate the sharpness of the lens in the centre of the frame. Detail produced by the two lenses at each of the three settings is fairly similar. It is also impressively similar to the Sigma 105mm f/2.8 Macro EX DG, which is our standard lens for shooting the charts, up to the 32 marker. As expected, there is a drop-off at f/2.8 and f/22, where image detail is softer. The Tamron lens is at its sharpest between f/5.6 and f/11.

Vignetting is obvious at f/2.8, with reduced brightness covering a large area of the corner portion of the frame. By f/5.6 the effect has all but gone, and by f/8 it has disappeared completely for consistent edge-to-edge brightness. This is not unusual for a lens of this type. Unprocessed raw files show chromatic aberrations in details like the edges of tree branches in the form of red and green fringing. This is more severe at wider focal lengths and towards the edges of the frame.

Images taken in our studio to test the level of distortion indicate that there is the expected barrel distortion at 24mm, but this is not drastic by any means. In real-world images, one can see the effect of barrel distortion in the corners of the frame where objects are stretched, but detail here is still crisp. At 50mm there is virtually no distortion across the entire frame, while at 70mm there is just a minor amount of pincushion distortion.

As a lens that will inevitably be used for portraits and shallow-depth-of-field work, I have looked at the quality of out-of-focus areas. Tamron claims that the nine diaphragm blades are rounded to give pleasing out-of-focus areas (bokeh), which mainly proves to be the case. In certain images shot at f/2.8, however, such as backlit gaps in between leaves in a tree, out-of-focus areas have a strange orb-like appearance.

We spoke to a representative of Tamron Japan, who states that this ‘onion’ effect is not unusual or specific to Tamron, but I took the same image on Canon’s equivalent lens and it does not show the same effect. Other than this specific scenario and exposure, though, I am pleased with the bokeh.

Image: The Tamron lens has pleasant bokeh, although in this situation, at f/2.8, the out-of-focus areas have an orb-like appearance

Our verdict

Image stabilisation is deemed surplus by many in a lens like this, but I find it useful for low-light work as it increases the versatility of this high-quality, general-purpose optic. Build quality is good, although I would like to see a couple of tweaks to the handling, such as a wider focus ring.

Image sharpness virtually matches the Canon equivalent optic, and the Tamron model is capable of some impressive results. It is not without the usual distortions at wider focal lengths, however, and at f/2.8 watch out for certain out-of-focus areas.

The Tamron SP 24-70mm f/2.8 Di VC USD is not cheap, but with its sharp results, good build quality and image stabilisation, it is good value.