Tamron is a third party manufacturer that makes a range of lenses to fit the main manufacturers' cameras. The 28-75mm Tamron lens comes with a Canon, Nikon, Pentax, or Sony mount, and it is equivalent to a 45-120mm lens on a full frame camera (if using on a crop frame camera). However, the lens is designed to work on both full and crop frame cameras. Regardless of the format, it covers the focal lengths suitable for portraits.
Pros
- Quick and sharp autofocus
- Fixed f2.8 aperture throughout zoom range
Cons
- Some reports of inconsistency between individual lenses
- Notable softness in the corners
Tamron SP AF 28-75mm f2.8 XR Di LD Aspherical (IF) Lens Review
No lens is perfect, but the Tamron lens does offer a lot for its price tag. It's a good all-purpose lens which will suit camera users without a massive budget ... and its autofocus takes some beating!
Build Quality
The lens is made of plastic, with a metal mount and rubberized zoom control. It offers a sturdy quality, but feels very light weight and easy to hold. There's a nice feature that enables you to lock the lens into place at 28mm, so that it doesn't extend when being carried pointing downward.
The "Di" in the lens name stands for Digitally Integrated Design, which helps to reduce ghosting, flare, chromatic aberration, and peripheral light fall-off. It's a feature that works well!
Autofocus
I was hugely impressed with the autofocus on this lens. It wasn't the quietest in the world, but it was extremely quick -- quicker even than some of my pro-level Canon lenses. It also coped well with differing light conditions. The only slight annoyance is that the autofocus ring turns while focusing, and it can't be grabbed in mid-rotation for manual focusing. Care needs to be taken not to touch the ring at all during focusing.
Optics
Center sharpness on the Tamron is good at all focal lengths, even at f2.8. Stopping down to f4 produces pin-sharp images in the center. However, there is a tendency for slight softness in the corners of the images. This is more noticeable on full frame cameras, and users of crop frame cameras may well get away with it!
There is some barrel distortion between 28mm and 35mm, but this isn't unusual in a lens of this class. Chromatic aberration (CA) and flare are well controlled by the afore-mentioned "Di," with only a little CA noticeable at 28mm. The lens' contrast is excellent, and far better than many others!
Conclusion
You won't find a faster autofocus on many lenses in this focal length range. The excellent contrast and lack of artifacts in this lens make it a strong contender for those on a budget. It's certainly just as good as many of Canon's and Nikon's own lenses in this price range. However, I have heard a few reports of people noticing large discrepancies between individual lenses, so make sure you test one thoroughly in the shop before buying, as quality control appears to be a slight issue. Apart from that, it's a good buy!