D800 fine tune focus on Sigma

[photomarche]

<p>Hi,<br>

I just bought the sigma art 35mm f1.4 ART to use on D800, and noticed a front focus issue.<br>

I tested it at f1.4 on tripod.</p>

<p><br /> After fine tuning the focus for this lenses to +20, it now looks ok. <br>

The other lenses I have are all nikon and they focus without need to fine tune. <br>

The camera itself was serviced few weeks ago and had the AF system check thoroughly, no issues were found.</p>

<p>I feel unconfortable with fine tuning the lens to this amount, do you find +20 an accetable value or would you return the lens insetad?</p>

<p>Thanks</p>

<p>Regards,</p>

<p>Francesco</p>

 

[Matt Laur]

<p>I use the same lens and it appears to be right on as-shipped. But I've got a couple of Nikon lenses that require almost all the positive fine tuning the camera bodies can provide. <br /><br />The good news about the Sigma is that you can buy their USB dock and use it to adjust the lens directly, as well as to use it down the road for firmware updates, no trip back to Sigma involved. <br /><br />Hopefully that new lens looks better than "OK," as I find it to be stellar.</p>

[mike_earussi1]

<p>AF variation is inevitable given how it works. If you're unfamiliar with that here are a series of very good articles explaining where the variation comes from:<br>

http://www.lensrentals.com/blog/2012/07/autofocus-reality-part-1-center-point-single-shot-accuracy<br>

http://www.lensrentals.com/blog/2012/07/autofocus-reality-part-ii-1-vs-2-and-old-vs-new<br>

http://www.lensrentals.com/blog/2012/07/autofocus-reality-part-3a-canon-lenses<br>

http://www.lensrentals.com/blog/2012/08/autofocus-reality-part-3b-canon-cameras<br>

http://www.lensrentals.com/blog/2012/09/autofocus-reality-part-4-nikon-full-frame<br>

http://learn.usa.canon.com/resources/articles/2011/1dx_af_precision_crosstype_article.shtml</p>

[michael_bradtke]

<p>Buy the Sigma dock and be able to fine tune the lens to your camera.</p>

[Andrew Garrard]

<p>I found that using the AF fine tune on the 35 f/1.4 sorted out one focal distance, but not others. I believe I'm not alone in finding this. I'm told the dock fixes it - I have it, but still haven't found free time to use it. I need to re-do all my AF fine tuning, really - but the Sigma dock is more flexible than the single number that Nikon lets you set.<br />

<br />

I have several images shot with the 35mm which are hugely out of focus. I've been using live view with it until I get the chance to set it up properly - that obviously avoids the problem.</p>

[robert_bouknight1]

<p>I have the Sigma lens and dock. My lens came to me "pretty good" but not dead on for close f1.4-2 work. I wound up with a little overall fine tune in the camera after tuning the lens with the dock per the Sigma procedure.</p>

<p>The dock tune procedure is somewhat biased to close focus distances where AF errors would likely be most noticeable.</p>

<p>If I had a new lens that took 20, I would probably return it. I do agree with Mike above, seems like most of my lenses are better with a slight tweak.</p>

[mike_halliwell]

<p>I guess, take 5 frames in AF with zoomed-in LV, camera on tripod, contrasty target, self timer, mirror up, shutter delay etc... blah, blah</p>

<p>Repeat with conventional AF...</p>

<p>If the former 'set' are better than the later, send it back.....if you can't tell ANY difference, then the AF is performing to the MAX ability of the lens.</p>

<p>As you can imagine, IF you could go to +25, it might be even better..:-)</p>

[alan_bessler_sr]

<p>It's a Sigma!</p>

[michael_bradtke]

<p>Nice contribution Alan</p>

[elliot1]

<p>If the lens is in perfect focus with +20, I wouldn't worry about it. It should not change over time. I had a Nikon lens that I had to dial in that much for proper focus. </p>

<p>But if you feel uncomfortable, exchange it.</p>

[lwg]

<blockquote>

<p>I found that using the AF fine tune on the 35 f/1.4 sorted out one focal distance, but not others. I believe I'm not alone in finding this. I'm told the dock fixes it - I have it, but still haven't found free time to use it. I need to re-do all my AF fine tuning, really - but the Sigma dock is more flexible than the single number that Nikon lets you set.</p>

</blockquote>

<p>I found the same thing, and using the Sigma dock has the lens focusing correctly at all distances. Now none of my lenses on the D800E need fine tuning in the camera.</p>

<p>If the lens focuses correctly at +20 at all distances I wouldn't bother to exchange it. The one you get might be like mine and require the dock to get accurate near and far focus with the same tune.</p>

[Andrew Garrard]

<p>Mike: I don't think <i>any</i> of my lenses hit absolutely perfect focus on my D800e without adjustment. I'd have sent back the whole lot by now if I had your requirements! There's a different optical path for the AF module and the sensor - there's no surprise that there's a difference, and it tends to relate to the telecentricity of the lens (which I gather is why the 80-200 AF-D has such issues). Some of my lenses are nearer to "perfect" than others, of course. My D700 seemed to be much more forgiving, probably because of the resolution difference (and because of the strong low-pass filter throwing away some of the remaining resolution).<br />

<br />

It remains a mystery to me why the fine tuning needs any user interaction. There's perfectly good contrast-detect AF, so it should be possible to point the camera at a target and let it sort itself out while toggling between AF modes automatically. Another one for the BIOS to-do list...</p>

[mike_halliwell]

<blockquote>

<p>It remains a mystery to me why the fine tuning needs any user interaction</p>

 

</blockquote>

<p>Indeed! Seems odd that none of the DSLR makers, but especially Nikon or Canon, have gone into the AF self-calibrate route. It would seem simple enough to implement and be a good selling point.</p>

[ilkka_nissila]

<p>I don't think it's just the resolution. I have the D3X and it certainly records enough detail to see focus offsets clearly. It has a much smaller span of the focus fine tune settings than my D800. My guess is that whatever Nikon did to change the Multi-CAM 3500 to be more light sensitive, also made it more sensitive to differences in optical paths of fast lenses causing all kinds of funny (not really) fine tuning to be needed with f/2-f/1.4 lenses (and some with f/2.8, not a severe; slower lenses seem to be mostly ok). The standard deviation of the fine tune setting over all my AF(-S) lenses is about twice that of the D3X. The D700 seemed to be similar to the D3X in its requirements i.e. apart from the 24/1.4 and 200/2, I didn't think fine tuning was of much use. I hope the D4s with its recalibrated AF system improves the consistency of AF across lenses, and a possible upcoming D800s might then inherit these changes as well.</p>

<p>Fine tuning could certainly be made easier for the user. Some photographers simply take their cameras and lenses to Nikon service who will fine tune them within the camera's warranty (and they can fix distance dependent errors, reportedly, as well). When I mentioned that my DC Nikkors have this type of problem using the D800 to a local authorized service center (i.e. 20 points of difference between infinity and close focus on the fine tune scale), they said they can probably fix it, asking me to bring them in but the problem is that I can never find the time where I don't need the equipment and I prefer the idea of user-configurability (but it has its limitations).</p>

[mike_halliwell]

<p>The Sigma USB Dock method of talking to and calibrating the lens's 'chip' seems to work well enough, but Nikon and Canon haven't followed on....yet.</p>

<p>I guess all Nikon and Canon 'old' lenses would all need re-chipping, where-as Sigma makes new, innovative lenses for all sorts of lens mounts and incorporated the things from the get-go.</p>

[Andrew Garrard]

<p>Ilkka - you may be right. I've certainly had more trouble with AF on my D800E than the D700 ever gave me - if you tell me it's likely to be more than the resolution and the per-pixel detail, I'm not going to argue. Though it's certainly a pain. I do notice some other weird issues - particularly, I believe (without an optical bench) that I have quite extreme field curvature out of my 14-24, and the 135 f/2 that I used to own was extremely difficult to focus and had heavy LoCA issues - more so than others seem to report. I'd wondered for a while whether my D800's flange distance was off (as someone once reported in these fora), but it's been repeatedly checked out (and then checked out again after I explained to Nikon UK that "field curvature" did not mean "barrel distortion"). When it works, it's an amazing bit of kit. Fortunately, I can usually get it to work well enough, although I seem to be fighting more than just the "perfect technique" required for 36MP...<br />

<br />

I believe the DC lenses are known to be a problem for the AF system. I don't think it's a telecentricity issue like the 80-200 - I suspect it's more to do with the residual LoCA; the manual does say something about not trusting autofocus with the DC setting at non-neutral. Good luck - I get the impression that most customers are happier than I was with mine.<br />

<br />

Mike: I believe Canon at least let you set a different AF offset at different zoom settings, which Nikon don't. Sigma have a full grid of values, which seems sensible, though I admit that I run out of knowledge before understanding how the lens could have more settings than the camera (or maybe the camera just assumes it can get everything from the lens - I really must read the AF-D documentation some time). The more flexible this is, the more of a pain for the user setting it is - which is why I wish someone would get around to automating it.</p>

[photomarche]

<p>Thank you all for the contribution. In addition to front focus issues, I randomly had blur shot at infinite under day light.... I eventually lost confidence in the product (this copy of the product) and returned it.<br>

Thanks again</p>

<p> </p>

[ilkka_nissila]

<p>At long distances / infinity, autofocus can be inaccurate (this is even in the manual!) ;-). Whenever possible, at long distances, use live view to focus.</p>

<p>Andrew, I don't know if my theory about the different versions of the AF module are correct. I now have a second f/8 capable Multi-CAM 3500 camera (the D7100) so I could do some additional testing to see if the characteristics of the AF system are similar to my D800's. In practice, even with the AF fuss, the D800 yields great image quality.</p>

[Andrew Garrard]

<p>Thanks, Ilkka - interesting to hypothesize, anyway! I've heard less about people complaining about the AF in the D7100 (or, of course, the other 24MP DX cameras that don't have AF fine tune), but that may be a function of the effective aperture/reduced width of the sensor. I certainly agree that the D800 is worth the trouble.<br />

<br />

At the risk of not having RTFM, is the infinity thing an issue with the lens or the camera? I'm hoping the dock can fix it, though I guess I don't often need fast autofocus to infinity!</p>

[alan_bessler_sr]

<p>Thank You Michael....</p>

[dan_south]

I picked up the Sigma 35 1.4 about a month ago. On my D800E, the lens required a +14 fine tuning adjustment. Without compensation it

was quite "fuzzy", but anything within +/-20 is within spec.

 

That said, I am planning to sell the lens. The lack of weather sealing is a deal breaker.

[mike_halliwell]

<blockquote>

<p>The lack of weather sealing is a deal breaker.<br>

</p>

</blockquote>

<p>Tell you what, just give me your D800 'cos that isn't weather sealed either. <br>

<br>

See that aperture-tab follower slot? Does that look weather sealed to you? Ha Ha! Forget it...!</p>

[dan_south]

Yes, I shall forget it, thanks for posting useless nonsense.

 

At least the D800 manual doesn't begin with PLEASE DON'T LET OUR PRODUCT GET WET, BECAUSE WE'LL

NEVER BE ABLE TO FIX IT. The manual for the sigma art lenses effectively says that.

 

If you want to take these lenses out to a wedding or a sporting event or a hike in the forest, great! Just pray for dry, dust

free weather.

[mike_halliwell]

<p>So Dan, your D800 <em><strong>IS</strong></em> weather sealed is it? I take it <strong ><em>the lack of weather sealing</em></strong> didn't stop you from buying a D800?</p>

<p>Anyway, phrases like 'resistant to' or 'weather sealed' are just weasely legalise fluff...unless it says WATERPROOF, they'll never cover anything if it drowns.</p>

<p>...even many of the new underwater, AKA WATERPROOF, AW1's leak after a few feet of immersion.</p>

<p>Nikon put their 'weather' text at the back of the manual instead....</p>

<blockquote>

<p>Keep dry: This product is not waterproof, and may malfunction if immersed<br />in water or exposed to high levels of humidity. Rusting of the internal<br />mechanism can cause irreparable damage.</p>

 

</blockquote>

<p>....and <em>irreparable damage</em> sounds alot like.</p>

 

<blockquote>

<p>BECAUSE WE'LL NEVER BE ABLE TO FIX IT<br>

</p>

</blockquote>

<p>Anyway, back on topic, if it can't be got back into focus with + or -20 with the in-camera AF Fine Tune, can the USB Focus Dock get it any <em>further</em>, ie does it extend the range of possible correction or just allow intermediate range adjustment?</p>

<p> </p>