How to get a 180-630mm f/2.8-4 stabilized Dx lens?

<p>I've been thinking about how to get a faster long lens without breaking the bank. I have the Sigma 120-400 f/4.5-5.6 HSM OS ($899 US I paid over a year ago) with my D300s, that gives me the equivalent of 180-600mm f/4.5-5.6, but just today I looked at the Sigma 120-300 f2.8 HSM OS and thought if I coupled it with the Sigma AF 1.4 teleconverter, I would have a 180-630mm f2.8-4 lens; 180-450 at f/2.8 (no tc) and 252-630 at f/4 (with tc), all for about $3250 US.</p>

<p>When I look at the prices for a Nikon 180 f/2.8, 300 f/2.8, 400 f/4 and 600 f/4, or the 200-400 f/4, it really gets me thinking. I guess the question is how much negative effect will a teleconverter have on the image quality? I've read some user reviews and most are very positive, with some complaining of build quality.</p>

<p>Leaving aside the fact that focal length doesn't change as a result of sensor size, only the field of view, let me ask: what are you planning to photograph with this thing?</p>

<p>I have the Sigma 120-300 f2.8 HSM OS and both the Sigma 1.4X and the 2.0X teleconverters. Image guality with the 1.4X is very good wide open and with 2.0X very good at f/8. Only cons are the weight (3 kg) and the shortening of the focal length at short distances. I've managed to carry it with 1.4X, Nikon D7000 + battery grip several hours with a BlackRapid strap style shoulder strap without remarkable shoulder pain, but I'm planning a new type of carrying system. The focal length of this lens is merely 285 mm at short distances, but doesn't bother you if you shoot at longer distances. This phenomena is present with many modern zoom lenses like Nikon AF-S 70-200/2.8 VR II. Price vs. quality is very good with this lens.</p>

<p>"<em>Sigma 120-300 f2.8 HSM OS and thought if I coupled it with the Sigma AF 1.4 teleconverter, I would have a 180-630mm f2.8-4 lens; </em>"- you would not have the f2.8 this way.</p>

<p>The 70-200/2.8 VR II Nikkor will be only 134mm long at close focus and setting zoom to 200 mm.</p>

<p>IMHO 3 grand is a lot to pay for the level of optical performance you'd be getting, even allowing for the dubious extra stop of speed.</p>

<p>You'll probably find that the lens+converter combination needs to be stopped down a further stop to give acceptable quality. This would leave you with a 168-420mm f/4 lens that was probably only useable at f/5.6 or below and with very noticeable pincushion distortion.</p>

<p>Multiplying the focal length by the DX crop factor is a bit delusional. The fact is it'll still only be a 420mm combo max.</p>

<p>OR ......</p>

<p>You could invest £600 on a Nikon V1/FT-1 combo and have 324mm - 1080mm without the image destruction of the TC.<br>

You 60 frames per second while you're at it. :-)</p>

<p>Pekka, thanks for the firsthand feedback. Frank, I think you missed that the 180 length is without the tc, my idea is to use the lens with and without the tc, depending on how much reach I need at the time (nature or sports), so the lens on my D300s would be a field of view of a 180mm and f/2.8. Rodeo Joe, has that been your experience with teleconverters, having to drop down stops and pincushion?</p>

<p>I know that lenses are the same focal length on any body, and I do understand the crop factor/field of view. To say that adjusting for the field of view is delusional is rather harsh. I used my D300s with a Sigma 50-150 (75-225 field of view) next to a friend with an Fx body and 70-200 and when looking at the shots, they are for all intends and purposes the same size in the frame. In my observation, $3250 is a reasonable amount to spend on this kind of setup.</p>

<p>Michael,<br>

you stated that <br>

"<em>if I coupled it with the Sigma AF 1.4 teleconverter, I would have a 180-630mm f2.8-4 l" </em>- and that is pure nonsense.</p>

<p> </p>

<p>In my usage the pincushion distortion is negligible (around 1%). Notice also that a new version of this lens was announced at the Photokina 2012 as well as Sigma USD docking system which allows you to adjust the focusing areas as you like with a new software SIGMA Optimization Pro 1.0.<br>

<br />-Pekka Lilja</p>

<p>Frank, you're taking that statement out of context, adding the sentence that followed clarifies what I'm saying, but to word it differently; with the 120-300 on my D300s by itself would be a 180-450 field of view at f/2.8, adding the teleconverter would make the same lens a 252-630 field of view at f/4, so with the lens and teleconverter, I have the versatility of a lens that can go from 180 f/2.8 to 630 f/4 just by adding or removing the teleconverter, which seems that much better than the 120-400 field of view of 180 at f/4.5 to a 600 field of view at f/5.6.</p>

<p>Again, Pekka, thanks for the firsthand feedback, it certainly makes me think that such a combination can work for me. The new one is the one in which I'm interested, and has a $200 US instant rebate.</p>