Cheap, lightweight, and decently sharp. Autofocus not ideal for wildlife

This is the THIRD time I have submitted this review to Epinions. My first review somehow vanished, only to reappear under, of all places, the Epinions listing for a SanDisk flash drive. I never reviewed that drive, and have no idea how my lens review got there. A second review mysteriously disappeared from the Epinions search results, though I can still access it from within my own account.

So ... I'm resubmitting a revised version of my original review. Please, Epinions, don't lose it again!

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I have used this lens on both Canon and Minolta/Sony digital SLRs. It is a good lens for the price, but falls short of greatness, due to slow autofocus, and on the Minolta, a marked tendency to front-focus. To some degree, these issues can be worked around, and its other features are quite good, notably its light weight (1237g, or 2.6 pounds) and good optical sharpness. To give you an idea how remarkably light the lens is, there is no other 500mm lens on the market that is under 4 pounds! As someone who likes wildlife photography but hates carrying heavy gear, this lens is almost the perfect solution, but as you'll see, the autofocus presents some serious limitations.

Nonetheless, this lens offers a lot of value for the money. It's pretty sharp for a zoom, and resolves details on par with top-notch zooms like the Canon 100-400L costing almost twice as much. The Tamron's contrast is lower than the Canon, and purple fringing is worse, but fortunately contrast is easy to fix in Photoshop, and purple fringing can be greatly reduced with the following free Photoshop plugin:

http://www.sd3.info/pf828/CAfree/CAfree0-1.html

Like many good telephoto zooms, the Tamron 200-500 is usable wide open, but improves one stop down. To see how well performance improves when stopped down, I've posted some 100% cropped images on my website to demonstrate:

http://www.geocities.com/tom_jhou/tamron_200_500.html

Optically, the Canon and Minolta/Sony versions of this lens perform identically, as you'd expect. However, Minolta/Sony DSLRs have anti-shake in the camera, and with a long lens like this, it is a godsend. It has saved my butt time after time, allowing me to get clean shots in poor lighting at around 1/200 shutter speed using my Minolta 5D. Combined with the lens' exceptionally light weight (compared to other 500mm zooms), antishake makes this lens makes an ideal handheld setup.

With Canon SLRs, I have to be much more careful when handholding. I need to keep the shutter speeds above 1/800 at full zoom, which requires subjects in full sunshine, or high ISO (800 or 1600).

With Minolta/Sony SLRs, the in-camera antishake makes this lens the cheapest way to get a long stabilized zoom. It's about half the cost of Canon's 100-400L, and still about $150-$200 cheaper than the new optically stabilized Sigma 150-500mm zoom, as well as being a pound and a half lighter. However, the tradeoff is the poor autofocus, which I'll detail in the next section:

Autofocus
The main downside of this lens is its slow autofocus, lack of autofocus limiter, and (in the Minolta/Sony version) tendency to front-focus. With the Canon version, focus is accurate, but too slow for flying objects like birds. Unfortunately, manual focus is difficult, as the focus ring is very close to the camera body, whereas one's hand naturally wants to support the lens near the end, far from the body. Depth of field at 500mm is also very thin, and I have to rock the focus ring back-and-forth repeatedly to get it right.

On the Minolta 5D, I found myself using manual focus even for stationary objects, as the autofocus consistently focuses in front of the point of interest, even under ideal lighting. I was surprised to see the misfocusing, as Tamron has a good working relationship with Minolta/Sony, and several Minolta/Sony lenses are actually rebadged Tamrons. Third party lenses often have electronic compatibility problems, but I'd expected the Tamron/Minolta combo to be better due to the close association between the companies. Guess not.

Interestingly, the focus plane is adjustable in Minolta (and Sony) cameras via a set of 3 hex screws under the sticker that surrounds the tripod mount. If you're willing to muck with your camera, you can make the Tamron focus perfectly as follows: Peel away the sticker around the tripod mount; you'll see 3 holes with a hex screw in each. Scrape away the glue holding each hex screw in place. Get a 1/16 inch hex wrench, turn counterclockwise about a quarter-turn. That makes the Tamron spot-on, but of course, it will make all your other Minolta/Sony lenses back-focus!

In the end, I gave up trying to fix the autofocus, and simply used manual focus with this lens. Either way, the focus issues make this lens frustrating for photographing animals that move quickly and unpredictably. It's OK in zoos, where animals will practically pose for you, but in the great outdoors, this lens' limitations are quite apparent.

Improvised push-pull action
Having used Canon's push-pull 100-400L lens, I like its ability to rapidly zoom in and out. It makes it easy to find a target at low zoom then quickly zoom in to shoot.

The Tamron is not marketed as a push-pull zoom, but it has that capability anyway. Simply grab the front of the lens, and apply force. The lens barrel will extend smoothly, turning the zoom ring as it goes. The motion is smooth, easy, and unforced.

Real-world example
The page I linked to above also has a handheld 100% crop of a cardinal taken under horrible conditions. It was cloudy and dark, and I had to use ISO 1600, but I was amazed this lens gave me anything at all - handheld! Here is the link again:

http://www.geocities.com/tom_jhou/tamron_200_500.html

Of course, I had to apply NeatImage and some sharpening, but the result isn't bad, considering.

Summary
If you're interested in telephoto lenses you will either pay a lot, or live with limitations, or both! This lens comes agonizingly close to the ideal handheld long zoom, especially on a camera with built-in antishake, due to its sharpness, low weight, and low price. Its achilles heel is that the autofocus is slow, lacks an autofocus limiter, and is not accurate on my Minolta DSLR (though the Canon version is accurate). If you have a Minolta/Sony DSLR, you'll really appreciate the in-camera antishake, but you may have autofocus frustrations unless you are willing to adjust the camera body specifically for this lens. Despite these issues, I have used this lens quite a bit, as it will deliver good images if you can manage the (difficult) manual focusing. To get much better optical quality, or focus performance, you'd have to pay a lot more, and deal with much heavier lenses that are harder to hike around with.