Rattling Sigma 17-50mm F2.8 EX DC OS HSM

[vikas_kohli]

<p>I got this from AbesOfMaine last week and have been using it with Nikon D7000. <a href="http://www.abesofmaine.com/item.do?item=SG1750OSAFN">http://www.abesofmaine.com/item.do?item=SG1750OSAFN</a><br>

Still haven't been able to say if I ike the results or not, as I see two issues :<br>

1. It seems to be focusing a little bit ahead (not behind) the subject. Like when I focused on my 2 yr old's eyes while he was doing something on laptop it focused on his arm as it was extended a bit and not on his eyes.. i was using it at f 2.8 sitting about 6 feet from him. I am using the manual focus point selection, then auto focus by using the AF-E/AF-L button.<br>

2. I hear an occasional rattling inside the lens body when I keep it vertical (lens up). Is this normal ?</p>

<p>Anyone has any suggestions ?</p>

<p>In the past I tried tamron's 17-50 VC but returned that as it was just not cutting it. This Sigma lens is definitely picking up colors much better as well seems sharper, but I don't want to loose on being able to focus where I want.</p>

[nishnishant]

<p>Like you, I have tried the Tamron 17-50 2.8 VC, but I returned 2 copies (both had issues - different ones). It's possible that I got 2 bad copies but that was too much of a coincidence. And now after reading your experience with the Sigma, I guess to be really safe you just need to wait for Nikon to add VR to their 17-55 lens. I wonder if it will ever happen!</p>

[vikas_kohli]

<p>I am going to Sigma due to the price differential, but at USD 670 a pop this is not that cheap either, so would expect Sigma to at least focus where I want. I love my Sigma 50 mm 1.4 and that was the only reason I tried it again at all !!<br>

When I did the cereal box focus test results were good, and I will be trying it out a bit more in next couple of days.<br>

I am hoping that out pn community will have some more hands on experience on this glass also and will be able to hear more about this lense </p>

[eric_arnold]

<p>hi vikas,<br>

i currently have the sigma 17-50 OS; previously i had the tamron 17-50 (non-VC). i'm liking the sigma more and more--initially i thought it was a bit warm in terms of colors compared to the tamron (which seems to be the opposite experience as you). it seems to be getting better with time, although i did have to turn down the in-camera saturation on the d90 (which is tweaked by nikon a bit more than the d300s is, straight out of the box). it is a very contrasty lens, and sharp in the center at 2.8 (although perhaps not quite as sharp as the 17-50).</p>

<p>on a d90 and d300s, focus accuracy has been for the most part dead-on. the d90 is not quite as good as the d300s in terms of AF, so i've kept this in mind. focusing on moving subjects is partially the camera, and if your sample is accurate on static subjects, but errs on moving ones, the lens may not be completely to blame. with the d7000, are you using one of the cross-type sensors?</p>

<p>with my copy, the AF is pretty snappy, and i've not detected any significant front or back focus -- which is also the case with my other sigmas (15-30/3.5-4.5; 15/2.8 fisheye, 50-150/2.8, 50/1.4, 30/1.4), which i'm using on a total of three bodies (2 DX, 1 FX). suffice to say i have confidence in sigma from personal experience, despite the Internet horror stories you hear. i don't doubt some people have had genuine issues but... i've bought many of these lenses sight unseen and two of them used. i'm actually on my second copies of both the 30 and the 50-150 (they were stolen) and had nary an issue with either.</p>

<p>one thing you have to watch out for with all cameras in terms of focus is contrast between foreground and background. if there's not enough, or not enough of an edge for the AF sensor to grab, the camera can misfocus or hunt. this happens more at 2.8 and other wide apertures b/c of narrow DoF.</p>

<p>if i were you, i'd do some more controlled tests with static subjects and then with moving subjects across an aperture range, making sure there's sufficient background contrast. it's always good to eliminate any possibility of user error before declaring a lens to be a dud. also,if i hold the 17-50 straight up and shake it, it rattles, but i don't make a habit of this.</p>

<p> </p>

[elliot1]

<p>Front and back focus can be a problem with the lens or camera, or both. You camera has the ability to correct for this. Look in the SETUP menu and select AF FINE TUNE and see if you can correct the problem. If you cannot, you may need to have the lens replaced.</p>

[vikas_kohli]

<p>Eric - thank you for your detailed reply.<br>

Yes, mine also rattles when I keep it lens vertical and have been so avoiding that now, but given that is the lense position in one of my bags I carry I guess I will need to change the bag ;)<br>

And I have been testing some more yesterday just as you said, to ensure picking upa high contrats point, and results have been looking better, and then I read your reply and I was all :)<br>

I wonder if it's a lens factor to be able to pick up contrasts differently ? as I don't see that as an issue with Nikon 35 1.8 and Sigma 50 1.4 but this one has it...</p>

[wogears]

<p>At the risk of being rude (who, me?), I must note that we have five previous posters in this thread. Four of these have no visible images, AFAICT, and the fifth has a page of test shots. First of all, how can we evaluate lens performance without pictures? I would humbly (riiight) suggest that the solution to all of the problems mentioned here is to go out and TAKE PICTURES. Stop swapping lenses in the vain belief that this will give you better pictures. If you have a SERIOUS concern about a lens, you have to subject it to a rigorous test procedure in which all variables besides the lens are removed (in so far as that is possible).</p>

[vikas_kohli]

<p>Les - as my pics are of family subjects I do not feel comfortable posting it here, but I totally understand where you are coming from. Eric's reply has been extremely helpful. I do not see any test shots at all..:) as I never posted any.<br>

I can actually post some pics of the static figurines. Any more details on "rigorous test procedure in which all variables besides the lens are removed" will be appreciated. </p>

[wogears]

<p>First of all...</p>

<blockquote>

<p>One thing you have to watch out for with all cameras in terms of focus is contrast between foreground and background. if there's not enough, or not enough of an edge for the AF sensor to grab, the camera can misfocus or hunt. this happens more at 2.8 and other wide apertures b/c of narrow DoF.</p>

</blockquote>

<p>This is flat wrong. ALL cameras and lenses will autofocus at maximum aperture--f2.8 in this case. They then stop down to the set aperture to shoot. There will be LESS hunting with a fast lens, because it is making more light available to the AF system.<br /> <br /> Test procedure: Shot a flat object with good contrast in diffuse (shade) light. Make sure the test object is vertical, and put the camera on a good tripod. Use Live View to focus for the first shots. This uses data directly from the sensor, bypassing the phase-detect (normal) AF which may be mis-aligned. Take three shots: maximum aperture; two stops down; four stops down. Now do the same thing using the camera's regular AF. If the first series of shots are sharp, then the lens itself is functioning correctly. If the second series is close to the first, then the camera's AF is working correctly <em>with this lens.</em> If the second series is softer than the first, then use your AF fine-tune to correct the problem.<br>

<br /> Most importantly: DO NOT OBSESS over this! Such obsession is dangerous to the craft of photography.</p>

[eric_arnold]

<blockquote>

<p>This is flat wrong. ALL cameras and lenses will autofocus at maximum aperture--f2.8 in this case. They then stop down to the set aperture to shoot. There will be LESS hunting with a fast lens, because it is making more light available to the AF system.</p>

</blockquote>

<p>les, we are talking about mis-focus, i.e. the lens or camera picking a focal point other than what the shooter intended. maybe you misread my answer, but at 2.8 and other shallow apertures, the plane of focus is not as deep as it would be at f/8. my experience is that <em>any</em> lens can hunt in low light or low-contrast situations, and i primarily use fast lenses--2.8 zooms, 1.4 primes, etc. if you combine low light, low contrast and shallow DoF, you can create a situation which induces mis-focus. that is all i was trying to say. i was not talking about brightness in viewfinder.</p>