3) Focus Performance and Accuracy
As a professional wildlife photographer, autofocus is one of the most important things that I look for in a lens/camera combination. These days, even the most basic lenses are capable of a solid focusing performance, primarily when used in good light. Where the top-of-the-line lenses come into their own (along with the better camera bodies) is in being able to focus accurately under challenging conditions. Conditions such as low light, fast-moving subjects, and complex backgrounds require lenses that make the most of the cameras tracking capabilities, and I am rarely satisfied with the performance of prosumer telephoto lenses in this regard.
Coming into this review, I was interested to find out how well the Tamron 100-400mm f/4.5-6.3 Di VC USD can keep up in demanding autofocus situations. Third-party lenses are not often able to keep up with the focus tracking performance of first-party lenses, and the Tamron also has a somewhat dim max aperture of f/6.3 at the telephoto end working against it. I have had good experiences with Tamron’s Ultrasonic Silent Drive (USD) autofocus motor in recent years, and after getting the chance to test the Tamron 100-400mm f/4.5-6.3 Di VC USD in the field, I can report that the overall performance is pretty good and a solid percentage of my shots were in good focus.
When shooting in One-Shot AF (AF-S), the lens focuses quickly in all but low light shooting situations and with good accuracy. However, things change when the light gets dim, and in such situations, the focus behavior is somewhat sluggish and you can expect quite a bit of hunting. This behavior is not unexpected for a slow telephoto zoom lens.
When shooting in AI-Servo (AF-C continuous) focus, the lens turns in a pleasing performance with fast focus acquisition speeds and pretty good focus accuracy. It has no problems keeping up with many subjects, and in most cases I got a good percentage of my shots in relatively sharp focus. The performance isn’t quite on the same level as Canon’s 100-400mm f/4.5-5.6L USM IS II, which is especially noticeable when the light gets dim, but Tamron lens is more consistent than the rival Sigma 100-400mm C lens in AF-C mode.
The below sequence highlights how well the Tamron lens deals with a typical bird in flight scenario.
4) Image Quality
The versatility of the 100-400mm focal length makes it highly adaptable for a range of photographic applications, but designing a lens with high image quality throughout the focal length range is a genuine challenge. Based on its highly attractive price and the success of the Sigma 100-400mm C lens before it, I was keen to find out just how well the Tamron 100-400mm f/4.5-6.3 Di VC USD performed when it came to its sharpness characteristics. I was especially intrigued to see how well it would hold up at the all-important 400mm focal length. In short, the Tamron lens is a very good performer in the center of the frame, while coming up short in the image corners.
At 100mm, sharpness centrally is excellent from f/4.5 to f/11, with a slight decline due to diffraction starting to show at f/11. The story is different in the periphery of the frame, where the lens is fairly soft. The corners of the frame only gain a very small amount of extra sharpness when stopping down, and you actually increase the level of lateral chromatic aberration as you stop the lens down at this focal length. At f/11 and beyond, diffraction starts to be a noticeable factor that limits sharpness.
At 200mm and f/5.6, sharpness remains excellent in the center of the frame. You gain very little if any extra sharpness in the center of the frame when stopping down. The quality in the periphery of the frame is a different story, and here we find fairly soft corners at f/5.6. Things do improve by f/8, but you really need to get down to f/11 for the corners to reach very good levels of sharpness. At that aperture, you get nice, even performance across the entirety of the frame.
At 300mm and f/6.3, the lens continues to perform well in the center of the frame with good to very good levels of sharpness. You gain a small but noticeable increase in sharpness in the center of the frame when stopping down to f/8. At this setting, the lens is capable of very high levels of sharpness indeed. On the other hand, the quality in the periphery of the frame leaves a lot to be desired, with soft corners at f/6.3. Things do improve a bit at f/8, but the lens never manages to get to good sharpness in the corners at the 300mm setting.
Where many 100-400mm lenses falter is at the 400mm focal length, but here the Tamron lens continues quite nicely with good central sharpness even at f/6.3. You gain a negligible increase in sharpness in the center of the frame as you stop down to f/8, where the lens continues to show good levels of detail. By f/11, we already see a decrease in the levels of sharpness due to diffraction. Image sharpness in the periphery of the frame is soft at f/6.3. Things do improve a little by f/8 and quite a bit more at f/11, where the corners are now on a decent level of sharpness.
Sharpness wise, the Tamron 100-400mm f/4.5-6.3 Di VC USD turns in a strong performance in the center of the frame while coming up short in the image corners. The high degree of sharpness at the center of the frame at the 100-300mm setting is especially impressive. The lens is also capable of good levels of sharpness at 400mm and f/6.3, though things don’t improve centrally as you stop down. Unfortunately, compromises had to be made, and the lens struggles to maintain a strong performance in the periphery of the frame, where it is fairly soft at all but the 200mm focal length setting. If this were a more expensive optic, I would place greater emphasis on this shortcoming, but given the Tamron’s bargain pricing, I feel that emphasizing sharpness in the center of the frame over that of the periphery makes sense.
The below unedited images show an example of the sort of sharpness that you can expect at the 400mm focal length.
5) Vibration Reduction
The Tamron 100-400mm f/4.5-6.3 Di VC USD comes with Tamron’s VC (Vibration Compensation) system. Tamron states that the VC system used on this lens gives about 4 stops worth of compensation. Shooting at 100mm, I was able to get a decent keeper rate at around 1/10 of a second. At 400mm, I made it to around 1/50 second. This performance seems to indicate around 3.5-4 stops of image stabilization, which while not class-leading, is quite good. There are two stabilization mode settings to be found on the lens, accessed via the VC switch. Mode 1 is your default stabilization while Mode 2 is for panning.
Zoom lenses of this type are not usually known for the quality of their bokeh, and the Tamron 100-400mm f/4.5-6.3 Di VC USD is no different. Variable aperture telephoto-zoom lenses tend to suffer from busy highlight discs with a pronounced “onion ring” effect, and the Tamron shows quite strong concentric rings in foreground specular highlights, with the effect less pronounced in the background. When it comes to the smoothness of the blur in areas of focus transition, the lens does a nice enough job of delivering a relatively smooth effect – though it can get quite nervous in certain high-contrast situations.
The lens exhibits a moderate amount of vignetting of around 1.5 to 2 stops at the extreme ends of the range, using the largest aperture. Stopping the lens to f/8 resolves most of the corner darkening, and by f/11 it is negligible.
Due to its complex optical design, the Tamron 100-400mm f/4.5-6.3 Di VC USD struggles a tad when it comes to its handling of lens flare, which is quite normal for a lens of this type. Tamron emphasizes their eBAND (Extended Bandwidth & Angular-Dependency) and BBAR (Broad-Band Anti-Reflection) technologies, which are said to improve handling of flare and ghosting. However, I noticed a very typical-for-telephoto-zoom performance against intense lights, with the usual flaring artifacts. On the bright side, contrast levels remained quite high.
Below is a crop from the center of the frame:
9) Chromatic Aberration
Modern lenses have become increasingly good at mitigating chromatic aberration, and the Tamron lens turns in a reasonable performance in this regard. Lateral chromatic aberration is well-controlled in the frame center, where it is virtually nonexistent. The corners of the frame show a higher degree of chromatic aberration (with moderate amounts popping up at 100mm and 400mm), but even at its worst, the performance is quite reasonable and easily corrected in Photoshop.