Introduction

Tamron SP AF 17-50mm f/2.8 XR Di II LD ASPH (IF) is one of the first 3rd-party standard zoom lenses designed for the APS-C size bodies. Prices at about US$370 (as of October 2007) the lens is quite affordable for the mainstream consumers.

The optical construction of the lens consists of 13 elements in 16 groups with a single eXtral Refractive lens elements, which helps keep the lens smaller when compared to alternatives using traditional glass elements, a single Low Dispersion glass element and two aspherical glass elements. The build quality of the lens is decent but not spectacular, resembling the quality of other consumer grade lenses from Canon, Sigma and other manufactures. Both zoom and focusing rings are rubberized and feel pretty smooth.

The lens is pretty light and compact, at least when the inner cams are collapsed, weighing 430g (15.2oz) and measuring 74 x 81mm (2.9 x 3.2in). However, the overall length of the lens almost doubles during zooming towards the long end of the zoom range. The lens sports AF as well as full time manual focusing system controlled by an AF/MF switch on the side of the barrel. The minimum focusing distance is 27mm, giving the maximum magnification of 1:4.5 at 50mm, the minimum supported aperture is f/32 and the filter size if 67mm.

Image

The factory box includes Tamron SP AF 17-50mm f/2.8 XR Di II LD (IF) lens, front and rear lens caps, petal shaped lens hood and warranty card. As mentioned earlier, the lens is designed to fit APS-C type cameras with smaller image sensors and cannot be used on full-frame bodies. The lens tested in this review was designed for Canon EF-S mount, but Tamron manufactures Nikon and Sony variants.

 

Summary
Lens Composition 13 elements in 16 groups
Angular Field ~78-31 degrees
Minimum Focus 27cm/10.6in
Focusing Action AF/MF
f-stop Scale f/2.8-f/32, camera-controlled
Filter Size 67mm
Lens Hood Petal shaped (included)
Weight 430g/15.2oz
Dimensions 74x81mm/2.9x3.2"
Lens Case None

 

Field Tests

The lens showcased pretty good performance in the field, with decent image quality at wide aperture settings and outstanding results in middle of the tested aperture range. The lens was at its best at the ends of the zoom range, with results in the center being somewhat less consistent.

The lens felt comfortable to handle, thanks to the wide rubberized zoom ring. I would not recommend holding the lens around the focus ring though - Tamron did not decouple it from the AF system, so the ring rotates during focusing. One disappointment is the AF system. While reasonably accurate, it is quite noisy and pretty slow. I also discovered that AF tends to hunt pretty much in all lightning conditions, which adds to my overall disappointment with the AF system on this lens. As mentioned above, the overall build quality leaves room for improvement - this becomes especially noticeable when the plastic filter ring attached to the front side of the inner cam starts to wobble during zooming, making a rather unpleasant scratchy sounds. Don't know if this is going to be a common problem for all samples of this lens though.

 

 

Vignetting @ f/2.8 - 1.6x crop (17mm vs 50mm)
Vignetting @ f/2.8 - 1.6x crop (17mm vs 50mm)

The lens showed very mild vignetting on an APS-C camera at the widest aperture level, which pretty much disappears by f/4. To my surprise (and satisfaction), the color reproduction was quite good, with excellent contrast throughout the zoom range and no major color fringing in the center and light fringing around borders at the wide end of the zoom range. At 17mm the lens showed slight barrel distortion, which is noticeable even to a naked eye, but things improve towards longer zoom range and by 24mm distortion disappears.

 

ISO 100, 1/1250, f/2.8, 17mm
ISO 100, 1/1250, f/2.8, 17mm

 

Tamron SP AF 17-50mm f/2.8 XR Di II LD ASPH image gallery...

 

Lab Tests

Please note that MTF50 results for APS-C and Full-Frame cameras are not cross-comparable despite the same normalized [0:1] range used to report results for both types of cameras.

 

Canon APS-C: Performance was all over the map, with no particular trend noticeable across the zoom range or the tested aperture range. Center performance remains pretty solid from f/4 through f/11 throughout the the zoom range, however border quality is somewhat sporadic. 17mm seems to be the lens' Achilles hill - both center as well as border performance at 17mm is rather mediocre throughout the zoom. The lens achieves its best overall performance around f/5.6. Here the lens can deliver excellent 19in and decent 24in prints (under the right circumstances of course). Conclusion? Results are not the most consistent, but at its peak Tamron SP AF 17-50mm f/2.8 delivers results that would fall into the top quartile of EF-S type lenses.

 

MTF50 (Line Width/Inch on the Print) @ 17mm
MTF50 (Line Width/Inch on the Print) @ 17mm

 

Normalized raw MTF50 @ 17mm
Normalized raw MTF50 @ 17mm

 

MTF50 (Line Width/Inch on the Print) @ 24mm
MTF50 (Line Width/Inch on the Print) @ 24mm

 

Normalized raw MTF50 @ 24mm
Normalized raw MTF50 @ 24mm

 

MTF50 (Line Width/Inch on the Print) @ 35mm
MTF50 (Line Width/Inch on the Print) @ 35mm

 

Normalized raw MTF50 @ 35mm
Normalized raw MTF50 @ 35mm

 

MTF50 (Line Width/Inch on the Print) @ 50mm
MTF50 (Line Width/Inch on the Print) @ 50mm

 

Normalized raw MTF50 @ 50mm
Normalized raw MTF50 @ 50mm

Chromatic aberration was relatively low in the center throughout the zoom range, never exceeding ~0.4px. CA around borders is a different story though. At f/2.8 CA around borders is highest, especially at closer end of the zoom range where it averages ~1.3px. CA is reduced with stopped down aperture, especially towards 50mm end, where it averages ~0.5px from f/4 through f/11.

 

Here are 100% crops, taken with APS-C type Canon Digital Rebel XTi, comparing image borders at f/2.8 and f/8

 

Image borders @ 17mm (100% crop): f/2.8 vs f/8
Image borders @ 17mm (100% crop): f/2.8 vs f/8

 

Image borders @ 24mm (100% crop): f/2.8 vs f/8
Image borders @ 24mm (100% crop): f/2.8 vs f/8

 

Image borders @ 35mm (100% crop): f/2.8 vs f/8
Image borders @ 35mm (100% crop): f/2.8 vs f/8

 

Image borders @ 50mm (100% crop): f/2.8 vs f/8
Image borders @ 50mm (100% crop): f/2.8 vs f/8

Alternatives

There's one ring, ughm, I mean lens to rule them all when it comes down to lenses designed for APS-C type cameras, and that's Canon EF-S 17-55mm f/2.8 IS USM. While almost three times more expensive then Tamron's 17-50mm f/2.8, Canon's alternative exhibits outstanding image performance, solid build quality and packs an image stabilizer along with an excellent (and silent) USM-type AF system. Outside of the APS-C camp, you might want to take a look at Canon's excellent EF 16-35mm f/2.8L II USM, which unfortunately costs even more, but also sports excellent image/build quality. Depending on the size of your budget, you might want to take a look at Canon EF 17-40mm f/4L USM and Sigma 17-70mm f/2.8-4.5 DC Macro HSM. Finally, for a super wide zoom, consider Canon EF-S 10-22mm f/3.5-4.5 USM as well as Sigma 10-20mm f/4-5.6 EX DC HSM.

 

Recommendation

Putting aside such glaring issues as build quality, noisy and slow AF, Tamron SP AF 17-50mm f/2.8 XR Di II LD ASPH IF is capable of producing pretty good results. Unfortunately, the performance is rather inconsistent across the zoom and aperture ranges. Hence if you're holding high hopes for the lens, you might get disappointed. Nevertheless, considering the relatively affordable price, Tamron 17-50mm f/2.8 can be an attractive choice for first timers and those of us on a budget.