Review: APO 100-300mm f/4D EX HSM Sigma. Sharpness on a Shoestring

Summary:
I bought this lens to replace my AI-S 100-300 mm. f/5.6 Nikkor. Nikon currently does not offer any lens in this range, while the 200-400 f/4 zoom or the 300 and 400 mm. f/2.8D primes all cost from $ 4.000 up.
That kind of cash does not fit my budget, while such an investment could not be justified due to my infrequent use of this type of lenses. To my own surprise, however, I have used this lens much more often than my old 100-300 Nikkor.

I decided on this Sigma based on the user ratings and great review it had at photozone.de, and have not regretted it for a minute; in fact, my buying decisions from then on have always weighted in this site's ratings and I've never gone wrong.

This lens is SHARP, even wide open. Sweet spot comes very early on, f/5.6 - f/8 depending focal length, and on the right camera it is blistering fast.
Some people have said this lens is not that fast, but on my Nikon D1x, D200 it focuses instantaneously (as fast as my AF-S 17-35 f/2.8D Nikkor); and is still reasonable fast on my D40, on which I can use it thanks to the built-in HSM (Hyper Silent Motor) auto-focus motor. The image below was shot with this camera.

My only regret is that it has no focus range limiter, which can complicate re-acquisition when you lose track of fast or erratically moving objects.
Works flawlessly with the Sigma 1.4x EX tele-converter, with no noticeable impact on focusing speed or accuracy. You lose 1 stop (f/max becomes 5.6), and some contrast.

Strengths:
• Outstanding build quality & finish, speed and sharpness.
• Can be used on both full-frame (FX) and APS-C (DX) cameras.
• Internal focus, no rotating / extending of the front-end. You can use polarizers and grad filters, if you can find – and are willing to pay for – any to fit the huge 82 mm filter thread
• Of course it's HEAVY, but it's also quite well balanced on all my cameras except the D40 (for obvious reasons)
• The absence of image stabilization (VR, OS, OIS) can be an advantage for some in terms of weight and cost
• Works in AF mode with the Sigma EX 1.4x tele-converter. (Only in MF combined with the 2x TC)
• Cheap top performance when compared to similar pro lenses
• 11 cm, Petal shaped sun hood included (image below)

Weaknesses:
• Chromatic aberration and purple fringing on some occasions, especially wide open, but this can be easily corrected in post. On the Nikon D300 and D700 this can even be done in-camera (only with JPG, unfortunately)
• No focus range limiter.
• Tripod socket is by far the weakest design element of this lens. I would suggest anybody who is planning to use it regularly to get the better, longer TS-41 model, which includes a shoulder strap (Yes: a bit of an investment @ 135 US - but worth it, IMHO)
• No built in image stabilization can be an disadvantage for some users who need the 1-2 stop gain one typically gets with VR lenses.
However, with the clean High ISO performance of the Latest Nikons (D3X, D300, D700), you can get the same gain upping ISO…
• Minor, expected, quality loss when combined the Sigma EX 1.4x tele-converter; f/max goes from f/4 to f/5.6.
• Expensive compared to similar consumer lenses.

Conclusion:
Optical quality: 4.5* (compared to lenses in the same price-bracket)
Build quality: 5
Design: 4 (so-so tripod socket, no focus limiter).
Value for money: 5
* 1 = poor, 5 = excellent
Highly recommended

See also:
Sigma discontinues the 100-300 f/4. Time to call upon Nikon for an affordable 500.

Pro Reviews:
http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/369-sigma-af-100-300mm-f4-nikon
http://www.ephotozine.com/article/Sigma-100300mm-f4-EX-DG-HSM-4464
http://slrlensreview.com/content/view/184/74/

User Survey:
http://www.ww.photozone.de/active/survey/nikon
Score: 4.27 (Very Good). This is as good as the AI-S 50 mm. f/1.4 Nikkor, which gets the same rating.