Sigma AF 400mm F5.6

<p>I am considering this Sigma lens. I am not sure if it is an APO lens. Is there eny difference between the non APO and the APO?</p>

<p>In brief, the APO macro is a very good lens, the other iterations of the Sigma 400mm are not.</p>

<p>All versions for Nikon use the body's screw drive for autofocus. I found the lens (APO version) very slow to focus on a D90, and thus difficult to use for birds. May be suitable for other subjects or with a body that has a stronger focusing motor. Focus is slightly off in attached image.</p><div></div>

<p>Sigma produced this lens in both APO and "ordinary" versions. The Apo version was a light grey colour and the normal lens had a black finish, but the real giveaway is the word "Apo" printed on the barrel of the Apo version.</p>

<p>As stated above the Sigma Apo 400mm f/5.6 is a good lens<em> if you can find one in mint condition</em>. Check that the infinity focus is where it should be and that the lens hasn't gone misty inside since those are common faults with this lens.</p>

<p>There are 3 APO versions, the regular APO, the APO tele macro, and the rare APO HSM. There also is a non APO version. The non APO and the regular APO do not have a good reputation, the APO tele macro and the APO HSM are the same optically and quite good lenses. </p>

<p>I have the sigma 120-400 OS HSM last version and very happy with it. AF is a lot faster than my old Nikkor 80-400 (I sold) and it is sharper too.</p>