Sigma 50 1.4 shift focus

<p>Hello!<br />I bought sigma 50 1.4 lens for my Canon 5d MKII.<br />It's have shift focus. I calibrated lens in 3 different services and they didn't fix it.<br />I sold this lens and bought new copy on b&h.<br />Same problem. I just bring the lens from authorized service center and they told me they can't fix it again.<br />I live in Russia, Moscow.<br /><em>Maybe I have any problems with my camera?</em><br />I used Canon 50 1.4 before and there were not any problems with autofocus.</p>

<p>Hi, search some threads on this lens and you will see you are not alone. This apparently is part and parcel of life with this lens, with many having the problem and some not. After seeing the optical quality and hearing about the mechanical quality I would have purchased it in a minute but I don't have the patience for evaluating, sending back, evaluating another copy, sending back, etc. My life is too busy. </p>

<p>My suggestion: send it back to B&H and use the Canon 1.4 or spring for the 1.2 if bokeh and build quality are worth a lot to you. I'm going to borrow the Canon 1.2 in the near future but you can read about it in many threads and on B&H now, my additional comments can't add anything meaningful, so much has been written. </p>

<p>Focus shift can be frustrating, but is not limited to the Sigma. I have been fine shooting wide open with it, and the problem distances are under twenty feet, but using aperture of 5.6 or so helps. Focus confirmation stopped down is a good tool too. There are some really good articles out there on focus shift, and they generally identify the large aperture 50mm as the worst offender regardless of brand, but getting much better with 85mm options. The Canon 50mm models have this problem too, and a search will show that people have made controlled side by side comparisons proving this. The Sigma is a great lens, I just got bored with the weight of it.</p>

<p>I agree with the post above about stopping down and focus shift being an issue with such fast lenses. I have the Sigmalux and its by far my most stunning lens but it does require careful handling. I generally try to stop it down to at least F4 when I can to minimize focus issues as well as depth of field issues. When used carefully though its a pretty awesome piece of glass.</p>

<p>Just as an illustration this shot was at f4 which is about as low as I go when up close.<br>

<img src="https://lh3.googleusercontent.com/-OdhLCYL7A7o/TO6rKaiP4bI/AAAAAAAA9Fw/CWu0FwHRF5M/s600/IMG_7184.jpg" alt="" /><br>

5dc and Sigma 50 @f4</p>

<p>Well, I guess you should go back to the EF50/1.4 - not nearly as good WO, but hopefully you'll be able to hit the focus w/ that lens -- until the AF freezes solid ;-)</p>

<p>Does your camera body support MFA? I found that adjusting on this lens was an absolute must for close in work. In fact, I've found that ALL my fast primes have yielded an improvement as a result of MFA, but for the Sigma, it was really apparent. Of course stopping down does make things easier too... </p>

<p>I have this lens and haven't had any issues with it. When taking landscape pictures I often visually check the focus after the camera has focus (I do this for all my lenses, not just the 50mm). I also have a split prisim focus screen installed to make visuall verification easier. If I am using a tripod the focus is always correct. When using the camera hand held I have more focus misses due to the narrow depth of field, camera shake, and user error.</p>

 

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<p>Focus shift can be frustrating, but is not limited to the Sigma. I have been fine shooting wide open with it, and the problem distances are under twenty feet, but using aperture of 5.6 or so helps.</p>

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<p>Note the phase detect autofocus system always focuses with the lens wide open. The aperture only stops down when the shutter is opening for the picture. So setting the aperture to 5.6 will have no effect on the focus. It will however increase the depth of field. The camera will only focus with with the aperture stopped down when live view and contrast detect is enabled. However there are several live view focusing options and not all will focus with the aperture stopped down. You will have to consult your manual to figure out which one (my camera is an older model without live view. </p>

<p>Question, how does the aperture effect the focus? It isn't attached to any lenses so when it moves the lenses elements don't . I have never seen a lens with a noticable focus shift. However the aperture, distance between the camera and subject do effect the depth of field. Furthermore depth of field is not always 50% in front and 50%behind the focus point . The depth of field behind and in front of the focus point will change dramatically with camera to subject focus distance. A lot of people may be thinking they have a focus shift when in reality they it is a change in depth of field that they were not expecting.</p>

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<p>f4 which is about as low as I go when up close.</p>

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<p>Well, I have to say it sounds pretty disappointing having to stop down to f4 in order to hit focus with an f1.4 lens. I find the Canon 50/1.4 pretty good myself.</p><div></div>

<p>Robin and Stephen:</p>

<p>http://diglloyd.com/articles/Focus/FocusShift.html</p>

<p>http://toothwalker.org/optics/spherical.html</p>

<p> </p>

<p>It looks like I shot at either 1.4/6.3/7.1 for my keepers with the Sigma lens versus 1.4/4.0/5.6 with the Canon 50 1.4. Not much difference in the images either, but I am always struck at how shallow the depth of field is within ten feet even at f/6.3. Handheld example of mine taken outdoors using AF and strobes, manual exposure, and the Sigma at 6.3 on a Canon, with crops from the original edited a few years ago:<br /> <img src="http://d6d2h4gfvy8t8.cloudfront.net/14302832-lg.jpg" border="0" alt="sigma 50 6.3.JPG" width="618" height="780" /><br /> <img src="http://d6d2h4gfvy8t8.cloudfront.net/14302834-lg.jpg" border="0" alt="sigma 50 crop sharp.JPG" width="561" height="561" /><br /> <img src="http://d6d2h4gfvy8t8.cloudfront.net/14302833-lg.jpg" border="0" alt="sigma 50 crop oof.JPG" width="561" height="561" /></p>

<p>I just did a quick test of some lenses (Sigma 50/1.4, Canon EF 35/2.0, EF 85/1.8, EF 135/2.0L, EF 24-105L and Sigma 180/3.5 macro). Focusing distance ca. 50 cm and ca. 100 cm. focussed once (lens on manual focus) and took shots between full opening and f/16. Subject was a ruler. All abovementioned lenses showed some focus shift. 50/1.4 was the worst in this respect, the 180 macro the best, together perhaps with the 24-105 and the 35/2.0.</p>