Sigma 35mm f/1.4 DG focus issue on D800E

<p>I received my new Sigma 35mm f/1.4 lens last week. I am pretty happy with the image quality, but I am having issues with the Auto Focus on my camera.<br>

At close distances (a few feet) it requires no AF fine tune, but at infinity it requires -11. Essentially I can't get it to focus correctly at all distances.<br>

Has anyone else seen this issue? Any solutions? Should I send it back to B&H for an exchange (where it's back ordered), or send it to Sigma? If other's have had this issue and had it resolved I would love to here from you.<br>

I wrote this up with some examples at http://www.trippingthroughthedark.com/sigma-35mm-f1-4-dg/</p>

<p>I have the same lens but have not had any of the problem that you are showing. Now granted I am only using a D4 but I have found this lens to be very sharp with accurate focus. I am just wondering about the sign image. Did you focus and then recompose the shot? If so that may explain the apparent back focus.</p>

<p>I guess if I really thought this was a problem I would contact Sigma and see what they have to say. You also have the option of waiting till they release the USB dock for this lens and then you will be able to adjust the lens parameters yourself.</p>

<p>I'm glad to here that all lenses don't have this issue. I'm sure the D4 would show the same issue. Things are still not sharp down sized to 9MP. Knowing that I will probably contact Sigma regarding the issue. I just fear getting stuck with a lens that can't be fixed. But that's probably an unrealistic concern.<br>

Regarding the sign image, no I didn't focus and recompose. I also took many pictures to verify this, so it's not just a one off issue. I just didn't post every shot. I should have mentioned that. Thanks.</p>

I would return it, wait at least three months and get another one. Let other pioneers test the early samples.

<p>That does sound like a lens issue to me.</p>

<p>Nikon (as far as I'm aware) doesn't post the maximum aperture their camera's can autofocus but Canon does. Canons can autofocus from F2.8 - F5.6 (some to F8) which means, with Canon if you have a faster lens than F2.8 the autofocus system isn't sensitive enough and will autofocus it as if it were F2.8 which will show up as some looseness particularly shooting at F1.2. I would suspect Nikons autofocus is similar, the autofocus is only good to F2.8 and on the D800E in particular will show up as being a little loose shooting at F1.4.</p>

<p>Knowing the autofocus is only as tight as F2.8 I would do the testing at that aperture. What happens if you aim it at the sign at F2.8 is the background still sharper than the sign itself? If you find the same result at F2.8 I would say it's the lens. If it doesn't occur at F2.8, then it's the autofocus is a bit loose when the lens is set to F1.4 and the effect being exaggerated by the amount of detail the D800E captures.</p>

<p>Hmm. I have exactly that problem with my 80-200 AF-D, though that's so far off that I can't fix the focus at all at close distances; I've heard this is a normal part of the optical design (something to do with telecentricity), but maybe it's just an assembly glitch in your lens. Sounds like Nikon could do with introducing more than one adjustment value (one for up close, one for infinity). Canon have a zoom-dependent correction, but I've not heard of a distance-dependent one. Presumably the problem goes away in live view focus, but I appreciate that telling every DSLR owner that they should use their lenses without phase-detect focus isn't really an acceptable solution.</p>

<p>I have a similar shot taken at f/4, and the same thing happened - the background is sharper than the sign.</p>

<p>Interesting thing about the AF having a maximum aperture. I've never seen this number published for Nikon cameras, only the minimum of f/8 for the D800E. In this case i don't think that's the issue since it seems to nail the focus consistently at close distances (or far if I set the Fine Focus adjustment).</p>

 

<p>Matt: I don't believe Nikon's autofocus (or Canon's) is only "good to f/2.8". There are sensors on Nikon cameras and Canons which are enabled at f/2.8 (the centre few on the autofocus sensors with large autofocus point counts, in addition to those that work at f/5.6), and these rely, I believe, on light leaving the exit aperture of the lens at a wider angle than the slower lenses. This allows a more appreciable difference in focus, increasing the speed and accuracy of focus with faster lenses. That's not the same thing as saying that the autofocus mechanism can't position the lens accurately enough to get pixel-accurate depth of field placed correctly with a fast lens. Nikon would have much more problem with it's f/1.4 lenses, and Canon with its f/1.2 ones, if the focal plane was only guaranteed to fall in the depth of field of f/2.8 (even with "depth of field" defined as "resolution limited by the sensor pixel size" as opposed to a perceptual measure).</p>

<p>Oops: I owe Matt an apology. I was mistaking the cross sensors on the Multi-CAM 3500FX for ones which work at f/2.8 (since that's often been a distinction in Canon cameras). It may be that Nikon feels there's no benefit to explicit f/2.8 support, or maybe there's a sliding scale (since f/2.8 lenses do seem to focus faster). Still, I don't believe there's a direct correlation between the angle of the light leaving the exit aperture and the ability to achieve focus at a given depth of field - I think you can look at the f/5.6 output of a lens in a split-prism rangefinder and still get the focal plane accurate to better than f/5.6's depth of field at the sensor.</p>

It doesn't sound like the problem is slack in the camera's AF, because it sounds like the problem is consistent - one AF

tuning is needed close and another far. Maybe a test for AF slack would be to shoot a subject at medium distance many

times, first by focusing at minimum distance then autofocusing on the subject, then going from infinity focus to the subject,

and seeing if there are consistent results and if the two batches are different? Also, it probably wouldn't hurt to try the lens

on more than one camera, but it does sound like your sample has a very slight misalignment of an element.

<p>I'll have that very same lens in hand tomorrow, and will try some tests myself. Very topical for me!</p>

<p>Good thread. I am looking to purchase this lens for my Nikon outfit. I'm interested in what you discover, Matt. Thank you, in advance, for sharing your findings.</p>

<p>I called Sigma and tech advised this lens does not focus accurately with side AF points on the D800. Known issue. That a hardware fix will come and the lens can be updated by user or sent back to Sigma. <br>

I think the less price of the Nikon 35mm f/1.4 this month might warrant me to reconsider. IMO resale value of the Nikon will be better (%). And know that it will fire on all cylinders. <br>

FWIW, for AF fine tuning, I do not use it. Too many Nikon pros/techs advised against it for use at various apertures and other variables. I find the focus to vary from my D800 to D4 w same lens. Not to mention, it is then not applicable to zooms. Though 1DX has it now for various focal lengths. <br>

I like Sigma, have the 15mm fisheye, and real cool lens, but got it since Nikon did not have same or current v.</p>

<blockquote>I find the focus to vary from my D800 to D4 w same lens.</blockquote>

 

<p>Well, yes, the AF-fine tune is dependent both on the camera and the lens. Otherwise the manufacturers could just tell you how to make the adjustment... You've really not seen any of your lenses needing fine tuning on the D800E? I never bothered with my D700, but I wonder how many pros advising against it were trying to get diffraction-limited accuracy at 36MP. Each to his own, but I'd not necessarily expect the Nikkor 35mm to have perfect AF out of the box. I don't judge so much by brand - I have Sigma's 150mm OS macro (epic lens), 8mm fish-eye (decent), 150-500 OS (disappointing) and 28-300 in a Canon fit (paperweight). Nikon have their share of horrors too. Good luck with the fix!</p>

<p>Van, I also called Sigma and had a nice talk with the tech. As soon as I mentioned the camera and lens combination he assumed I was calling about the side AF points. I hadn't even noticed that they have problems, but a quick and dirty test confirms they are off from the central on close up objects.<br>

He said I could send the camera and lens in and they could tune the lens to match my camera. The turn around time would be quick. But I'm not sure if this would fix the side AF points. At this point the lens is going back to B&H and I'll decide if I want to get another in a few months, or just buy the Nikon.</p>

<p>Andrew, I have checked most of my lenses and surprisingly they all do better with AF fine tune turned off. This is in sharp contrast to the D7000 where every lens required some adjusting. But once they were adjusted they focused consistently well, so I'm certainly not opposed to using the fix if it's needed. I am using many of the same lenses on the D800E, so the need for an adjustment is certainly not based just on the lens. In fact it really seems mostly camera driven.</p>

<p>If I buy the Nikon I will certainly test it, and if it can be brought into focus at all ranges I will be happy. Same if I decide to order another copy of the Sigma.</p>

<p>Re the Sigma 35mm you commented on in your test, I would also return it. You should feel confident with your equip. I for one stay with Nikkor lenses. I tried the fisheye from Sigma and like it. I would have bought a Nikon version automatically if there was one current. But, I thought about the 35mm Sigma cause of the price. I have too many lenses now, but a sucker for a good prime lens deal. Might still try it. Not keen on the issue the Sigma tech advised, so probably will not try it Probably will try the Nikon 35mm. </p>

<p>Re the AF fine tuning. I have been told too many times, to stay away from it. And these are guys that work at Nikon and pros that earn money with their lenses. I don't know, maybe I am missing something, but sharpness from the lens is not an issue with mine. More so tracking the image, DOF settings, knowing the camera and settings available. I would recommend, instead of AF fine tuning, to really delve into the submenus, create various banks and better your AF settings right, especially if you shoot AF-C, which I do 90% of the time, I've found a big difference with tweaking the settings. There's a lot of settings for AF that will vastly improve the capture. Each lens has its issues, distortion, more or less sharp at certain apertures, etc. I have yet to find a perfect lens. Even Zeiss has some that are not great at certain settings or on particular cameras. Hate manual focusing now. Anyway, my 70-200 VRII is the sharpest of the bunch, can you believe, and I have the 200 f/2 and 200-400, and all the others. Go figure. But guess what, any image will be sharper with a tripod over any AF fine tuning you do, I say. Side note, I stay above f/8 for the D800 I have. Not an issue. But not more DOF with the D4 with any lens is a- ok. </p>

<p> </p>

<p>matt, what body will you be using your sigma 35 on? please post shots when it arrives. v. interested in this lens (for use on D3s, mainly).</p>

<p>Wow! Did <em>everyone</em> just buy this lens? I'll be getting mine in a few days. Will check and report results with my D800E.</p>

<p>Eric<br>

My copy of this lens works just fine on my D4. No problems with the side focus points.</p>

<p>

<p>This was focused using the far right focus point. Granted it is at minimum focus distance but the focus point does work. </p>

<p>Eric: Will try out the 35/1.4 on a D300, D3200, and (most interesting to me) the D600. Not only that, I'll take dog pictures with all three (this is <em>me</em> we're dealing with, here). </p>

<p>I use my D800E with the new Sigma 35 f/1.4 and the AF works perfectly at all distances. The left and right AF points focus accurately too. The lens is extremely sharp at f/1.4 in the centre and pretty good on the edges. It's razor sharp at f/4 to f/8. It's superior to my Zeiss 35/2, which I'm currently in the process of selling and that lens is better optically than the Nikon 35 f/1.4 I used to own. In fact, my Sigma 35 f/1.4 is almost on par with my Nikon 200 f/2 VR II at f/4.</p>

<p>Tech advised me, it was with the D800, not D4. I am going to get the lens and try for myself. </p>

<p>Well mine is heading back to B&H today. A local store will have one for me to check out early next week. Hopefully the new lens will focus correctly and I can get it. I really do like how the lens draws an image when it focuses correctly.</p>

<p>Does anyone understand how the Auto Focus system really works? It seems odd that the lens can play such a role in it. I would think that the camera would move the lens into focus and then stop when focus is achieved. But it's obviously much more complex than that, given that they can adjust the lens at different ranges. What seems really odd is how the LiveView focus with the lens was dead on every time I tried it. I know one uses Phase Detect and one is Contrast Detect, but both should just be moving the lens to the correct position. Since it can work in one system, why not in both?</p>

<p>LG, I don't understand, if the lens is sharp in live view, why did you return it? The AF system's side sensors fix only on vertical lines and the center sensors on horizontal and vertical lines. And if you are to close to the subject or the camera cannot differentiate you may also have a AF problem. I am not concerned about AF fine tuning. If that is your concern, maybe someone else can assist you. Since many have not experienced D800 issues w this lens, I don't know if the tech at Sigma mentioning D800 issues with the lens as I mentioned is isolated issues or not at this point. (side note I did not know a lens can be firmware upgraded via a USB download, he mentioned is in the works for this lens, kinda cool, I did it to my speed lights but not to lenses before) IMO, it sounds like you may need to set up the AF system custom settings. It may not be an issue on your other lenses, but on this one, or brand it may be. Meanwhile, I don't know why everyone is so bent on razor cutting sharpness. There's more to a quality lens, ie. color rendition, weather proofing, warranty, resale, CA, Bokeh, speed of focus, filter size, etc etc. Please let me know your results with another of the same. I am getting a Nikon and Sigma version myself to test. </p>