[Chako]

I know there are a lot of people that are interested in this sort of a focal range for a zoom lens, and at a good price point. I was looking at either the Sigma 70-300mm (either the plain or APO version) or the Tamron 70-300mm lens in a Pentax mount for a K10D.

After trying both out, I ended up buying the Tamron lens simply because the local photo store had one in stock. The Sigma would have taken 14 days to get in (the one I tried out was for a Canon mount). So I bought on convenience and a little knowledge from internet research.

After using the Tamron for several outings this is what I have found.

The feel of the Tamron is very nice. It is made from polycarbonate, but does not feel cheap at all. The zoom has a nice feel to it, as does the focusing ring. The barrel style lens shade does feel cheap however, made from a fairly light plastic. On the upside, the Tamron lens cap is intelligently designed (I wonder why everyone doesn't make theirs the same way). It is of the center pinch variety that allows you to install and take off with the lens hood in place. Very convenient.

The Tamron has a macro mode down to 1:2. Basically this will allow you to capture things down to half life size. Not a true macro, and more of a close focusing mode, but very useful. In fact, I have found that this lens is perfect for larger bugs such as butterflies, wasps, and dragon flies. The macro mode is enabled around the 300mm range which will give you excellent stand off distances for shy subjects. To be fair, the Sigma has the same feature.

I have found the Tamron to be very competent in taking photos. The focus is fairly quick, and I have not seen any hunting yet, but I haven't taken the lens out in darker conditions either.

The one flaw that I can see, is CA. I knew of this from reading on the internet, and it is true. This lens, in certain conditions, will get a fairly bad case of purple fringe. For instance, here is a crop of a photo I took in bright daylight. The bird was up in the trees framed against a bright sunny background. Perfect CA conditions and the lens did not disappoint.

Note the beautiful purple fringe running along the lower side of the tree branch.


With some post processing you can eliminate CA, or like what I did, just convert it to black and white, and you can still get a keeper without fussing overly much in eliminating it.



Overall, I have found this lens to be a perfect nature photography companion. It is just long enough to be of some use for larger birds, and definitely useful for flowers and larger bugs. It is well built and light weight. The lens cap is of a smart design and is convenient to use. The photos are very sharp with good definition for a budget lens.

With a lens of this price range, compromises are a sure thing, and with this lens, you can expect CA to rear its ugly head. There are ways to deal with it however, and I think you will find that this lens is very good value for money spent.

[Entropy]

I have the Quantaray-rebadged version of this lens, and my experiences are about the same. I have hit the CA occasionally, but on other shots I basically have zero CA. There are many shots where I see CA but it is in a place that isn't too distracting, while the subject is CA-free.

If you add a Tamron 1.4x TC to this, its macro performance is quite respectable. Still not 1:1, but the working distance is really nice. (I need to post some example shots and a shot of my setup showing the working distance).

Unlike you, I have had some focus hunting issues. For the most part it happens in lower-light situations with close distances when the lens started out VERY far from the necessary focal length. In situations like that, I quickly flip to manual and twist the lens quickly in the correct direction before flipping back to AF. (Note that I'm NOT manually focusing, I'm just giving the lens a roughly improved initial condition for AF.)

I have some extension tubes coming, of the cheapo eBay variety. Since the Tamron has an aperture ring unlike most new lenses, it will work far better with such el cheapo extension tubes.

[Matthew Roberts]

moves this up to at least second on my "to buy" list (close to the DA 50-200).

Nice.

[Entropy]

Yeah, unless you need the reach go for the 50-200 first. The IQ is somewhat better, but more importantly the DA is a LOT lighter. The Tamron is very big and heavy compared to the DA 50-200.

I own both, I like both, I've actually been using the Tamron more than the DA lately just due to the extra reach. The close focusing capabilities of the Tamron are quite nice too.

[Bramela]

I have been using this lens for a couple of months now and am quite satisfied with the results.
I agree, and have found myself, that purple fringing is a bit of a problem in certain conditions (bright and contrasty.) Against bright water background and the sky most obvious.
Have found that the macro capabilities are very satisfactory, rather than stunning
e.g.