Sigma 18-35 1.8 Focus Problem - only in view finder focus

Blckcat

Hi, I have been using my Sigma 18-35 1.8 with D7100 for my clothing photography for few months and I finally want to discuss about this issue.
The lens would focus perfectly in Live View. However, it won't focus on the object that is further than 1 yard.
I've tested my D7100 with other lens and they seemed to focus right.
Therefore, this isn't my D7100 problem.

Strange thing is that Sigma 18-35 CAN focus perfectly for objects within 1 yard in both Live View and view finder focusing.
It only have trouble focusing on objects outside 1 yard with view finder focusing -- Live View focuses perfectly though.

Do I need to send this in to Service Center?
Or am I doing something wrong?
Anyone have similar experience with 18-35?

Thanks

spraynpray

Although I considered this lens, I didn't get it - but my friend did. He was worried about it being reputedly slow to focus and sometimes missing focus (not your problem I know) but he has found it to be excellent - sharp, reasonably fast to focus and excellent from up close to infinity.

I suggest you send yours back for a check-over.

Ade

The AF calibration parameters are off. This will only affect "view finder" focusing.

Depending on the severity of the issue, you could try resetting the focus parameters using the Sigma USB dock ($60) or compensate for it using the D7100's AF Fine-Tune function.

Blckcat

@Spraynpray
The lens is phenomenal when focused right -- when using Live View that is.
It focuses perfectly and very fast for within 1 yard boundary. But further than that, its horrible.
But this weird focusing problem is driving me crazy! I use this for my work! I can't always be using slow Live View.

@Ade
I understand AF calibration could be one possible problem. But this is only happening for "Far away" objects that are more than 1 yard away! Could you call this AF calibration problem too?

I tried and AF Fine-Tuning Function did not help as this happens in certain distance only. If I get the "far-away" objects to focus right, then "Close" objects are out of focus.

Could this be solved using the USB Dock you've mentioned?

PB_PM

@Blckcat Yes that is a symptom of the AF not being aligned. That kind of issue is often more visible with zooms, which are often calibrated to focus the best at a particular focal length.

Blckcat

@PB_PM

That is very strange and hard to understand. If focus is not aligned, shouldn't it be same (not aligned) through out all distances?
What's the best solution for me?
Proper AF Fine tuning or Sigma USB Dock could help me do this without sending in for repair? Or repair could be a better solution?

I really enjoy this lens. It's fantastic and this is actually keeping me from switching to Full Frame... But I'm having difficult time working with this lens on Live View the whole time...

Thanks for helping!

PB_PM

@Blckcat Generally speaking zooms are set by the manufacture to focus most accurately at a given focal length (usually the middle of the range), and for a given distance.

There are tutorials out there that explain how to focus fine tune a lens. If using AF Fine Tune cannot rectify the problem, then you might need to use the USB dock, or send the lens to Sigma.

Ade

@Blckcat

The fact that you can successfully use AF Fine Tune to make far objects in focus (albeit sacrificing close objects) confirms that it's the AF calibration settings that are off.

With the USB dock you can specify different calibration settings for four different distance zones. So in your case you can put in a different calibration for distant objects (> 1 meter to infinity). Hopefully that may solve the issue. Otherwise sending the lens back for repair is the only other option.

See video below:



I wonder how the calibration settings got messed up to begin with... you may want to reset to lens to defaults and go from there.

heartyfisher

weird but the "symptoms" sound like you have an extension tube or close up filter attached...

Blckcat

@PB_PM
I see. Learning something new everyday I hope this would help others who're having trouble too.

@Ade
My searching skill must be terrible. I didn't know there was video like that. Thanks a bunch!

@heartyfisher
That's what I thought too.. but nothing was attached.

Vipmediastar_JZ

Maybe a silly question but does the Focus point cover the greater area that needs to be focused?

PB_PM

@Vipediastar_JZ it is important to remember that auto focus points are not boxes like what you see in the viewfinder, so that doesn't tell you the real story. Auto focus points are either a + shape or | shape.

Vipmediastar_JZ

@PB_PM thanks I never knew that. I always assume that's what it was and looking at ViewNX it was always square. I wouldn't mind reading up on these + or | shapes.

I guess the better photo that I was looking for is on the actual manual but I haven't found it online yet. In the manual it shows an example if the square is bigger than the subject it may not focus correctly.

PB_PM

@Vipmediastar_JZ This link gives you information on auto focus systems. The information is out of date, but part of the way down the page it talks about the shape of auto focus points and the difference between cross type (+) vs non-cross type ( | ) points.

Ade

The competition (with a "C") also has "dual-cross type" AF points... combining (x) points with (+) points to make a single * high-precision AF point, for lenses with max apertures of f/2.8 or larger.

Msmoto

@Ade
And, that is why we see so many gray lenses at the sporting events….many of the Canon shooters believe the focus is quicker on a Canon vs, Nikon pro body…… but we have the edge in sharpness overall…NPI

GreenFlash

I have this lens and I have the dock. The way the dock works for this lens is that you can set (and reset) the focus of the lens to plus or minus positions for four different distances. To do it right I made a jig with the distances marked on it and put items to be focused on at each of the distances. Took a couple of tries, but by the time I was finished the lens was tack sharp at every distance. I would get the dock and try it first, then if it still doesn't work, send it back. But a couple of other caveats. This lens has very shallow depth of field at low f settings. Using multi point or matrix focusing may just simply be focusing on something other than you want it to. So try different focus modes to see if that is part of the problem.

Reese

@PB_PM
I see. Learning something new everyday I hope this would help others who're having trouble too.

@Ade
My searching skill must be terrible. I didn't know there was video like that. Thanks a bunch!

@heartyfisher
That's what I thought too.. but nothing was attached.

So, I am currious, what was your finally conclusion to this issue? Did you send the lens to Sigma? I am in the same boat...

Sareth

Have you found the solution? I have the same issue focusing at long distance.

Pistnbroke

Like I said alway buy a Nikon Lens

spraynpray

Like I said alway buy a Nikon Lens

I only wish Nikon would service the DX range with lenses as good as the 18-35 Siggy. If they could improve the focus in low light, I'd be all over it.

Pistnbroke

If you look in the text of Nikon rumors blog today 150--600 you will see comments on adjusting the 35mm lens. Para 3.....It seems we have sharp lenses designed with large variations in back focus dependent on the distance focused on which need computer help to track that variation...Hence the USB base thing

Blckcat

@PB_PM
I see. Learning something new everyday I hope this would help others who're having trouble too.

@Ade
My searching skill must be terrible. I didn't know there was video like that. Thanks a bunch!

@heartyfisher
That's what I thought too.. but nothing was attached.

So, I am currious, what was your finally conclusion to this issue? Did you send the lens to Sigma? I am in the same boat...

Wow time flies. I completely forgot about this thread. Well, I still am using this lens and I'm afraid warranty has been expired ...

Since I used the lens mostly for studio work, I just used the Live View mode.

Occasionally, when I bring this lens along during my vacation, I had many blurry faces/subjects and it was quite annoying. But I still like the lens. I'm going to find out if I can get this calibrated using the USB. This lens is actually holding me back from getting a D750 right now..

I wonder why other companies aren't making 1.8 focal zooms?

Thanks

spraynpray

The Sigma 18-35 is renown for erratic focus - ironically, it's especially poor in low light. My mate got one for his 7D and it is unusable in church. I am told the problem doesn't exist at all with the primes, or it exists only slightly or it exists a fair bit depending on who I ask so I'll never own that zoom, but I am going to try the 35mm art prime.

funtagraph

A lens' AF is only as good as the camera delivers. Old 7D and several Nikon bodies were developed without a fast DX wide-angle zoom on the horizon. Maybe Sigma should have thought about that before they designed it. On the other hand, their own SD1 is far more outdated in terms of AF than others, so I wonder how the lens performs on a SD1

Blckcat

Hi everyone.

Just wanted to share my experience after sending my lens to Sigma for adjustment.

In short, I have to say, I think they nailed the focus problem. There still is a very tiny focus issue, but I think that's just the limit of my D7100's non-liveview focus. It focuses as well as my 35mm 1.8 Nikon lens -- if not better.

Sigma states that their lens' are fine-tuned to fit all DSLRs out of factory, but they say every camera require slightly different fine-tuning. If you have some time, send your 18-35 1.8 to Sigma for fine tune. I think its worth it. They may contact you for your camera's model number for specific adjustment (or I might have forgotten to supply them at first place..).

Not to mention you have 3 year extended warranty if you bought yours off the shelves of authorized store! Be sure to check it!! I thought mine was out of warranty but thank goodness I've bought it from authorized store (Samy's Camera).

I wanted to move up to FX but this lens is just too brilliant to sell off...

In conclusion, after having mine sent in, it's very satisfying.