Decentering issues - what to expect and accept?

[Lars Hansen]

Last winter I purchased an XF 55-200 zoom for my Fuji X-E1. Overall it's a great lens and I like the image quality I get. However my test shots at 200mm/f5.6 showed a tendency to blurriness/smearing towards the bottom of the images. I got it replaced and the new sample showed same tendency - now towards lower left side and even worse as it was also visible towards the center. I sent it for service twice without it getting fixed - both times I recieved a message saying that it measures to specification. I finally gave up and returned it.

This week I purchased a new one - thought I'd give it one more chance. Unfortunately I see the same tendency to blurriness/smearing towards left - however this time less pronounced. I've tested it with and without OIS. Sharpness is fine towards center and right side so it is not motion blur – I've also tested on tripod (without OIS). When I shoot subjects on larger distances it becomes more visible – always towards  lower left side. 

I've read that decentering issues is more likely on zoom lenses at the longest focal length. The Fuji zoom has an inner barrel made of plastic and it extends fairly long zoomed to 200mm. So if it's not caused by misaligned lens element(s), I guess this alone could lead to inaccuracies. I once had an 18-55 zoom where the inner barrel, when zoomed out, hit the outer barrel .. not a keeper. Another possibility is damage caused during delivery. 

I'm a bit torn - can't decide if I should return this as well. Maybe I just have to accept a degree of inaccuracy due to design, materials and the fact that zoom lenses are more prone to such  defects. Maybe this is close to as good as it gets with Fuji - at Photozone.de they have reported QC issues with Fuji lenses including decentering defects. However, it's becoming rather discouraging and tiresome having to test these lenses and spend ones time on replacement, service etc. My plan was to purchase the Fuji 10-24 zoom as well but now I probably wont. 

What are experiences and opinions wrt. decentering issues – is it something one have to accept and live with to some degree? Maybe a "perfect" lens is too much to ask for.     

[Bjørn Rørslett]

With the caveat* mentioned below, seems this lens might be a shoddy construction and doesn't stand up to normal use. The maker should improve it and might do so if a sufficient number of customer complaints are received. Or so we can hope.

A lens straight out of the box should work without any flaws. As these things are mass-produced, there will always be the occasional flawed or failing sample, but anything above say 1-2% risk of failure simply is too much and thus not acceptable.

^* for some strange reason most users never think their camera and its mount might be the culprit causing "lens" issues. A misaligned or warped mount is far more frequent that the general public realise. Do make a habit of having your camera checked at a qualified repair shop at least once a year.

[Lars Hansen]

Thanks Bjørn - the XF series is considered to be Fuji's top line of lenses. Hence the higher expectations. However it's my impression that decentering is not related to the price tag. When it was released, the Fuji XF 55-200 did have some quality issues that later was fixed so I've been wating a while to take the plunge - maybe I should wait a little longer.     

I didn't consider the camera mount as you suggest - but it makes perfectly sense that this could also be the culprit. Especially if the issue is related to a particular area of the image frame. I only have one camera body and I'm not planning to buy a new model until I have at least a basic set of lenses..   

[Akira]

I experienced similar decentering issue with Nikkor 17-55/2.8 zoom I had bought brand new.  It was decentered and AF was off.  It took two weeks to repair at Nikon under warranty (of course), but the lens was still decentered and couldn't focus properly.  My camera body at that time was D40 and it worked perfectly (I hadn't had any issues with any other lenses I had used with the same body).  I returned the lens and never bothered to try another one.

Recently the Camera Store TV (Chris Nicols) reported the quality control issue of the first batch of the latest AF-S Nikkor 24-70/2.8 lenses that they laied in stock.

I admit that my reaction to my own experience is excessive response, but I've been VERY skeptical about the zoom lenses since then.

[pluton]

When the defect or design flaw manifests itself at the very setting that you need to use with the lens, you'll never be happy.  Using the lens will be torture.  Return it, and either try another one, or look for another solution.
As suggested by Bjørn R., it would be prudent to also have the parallelism of the body flange to focus checked also....just so you can be sure it's not the body.

[Frank Fremerey]

I bought a 1.8/50G new with strong right/left decentering factory new. I gave it to Nikon Service but did not test it yet. They said they healed the thing. For free of course

[Bruno Schroder]

LensRentals has an excellent post on home testing for decentering: http://www.lensrentals.com/blog/2014/02/setting-up-an-optical-testing-station
and a real case of shock induced tilting, with pictures and testing: http://www.lensrentals.com/blog/2012/08/a-tilted-element-demonstration

[Bjørn Rørslett]

I heavily used my AFS 200/2 Nikkor VR (Mk.1) for about 10 years before the first signs of uneven sharpness indicative of decentering occurred. Did the lens got beaten up over these year

It went for a refreshing vacation to Nikon's Swedish repair facility, where they have the added instrumentation to handle such problems properly. Set me back plenty of $$, but lens quality is sparkling again.

My point is that optical decentering can occur on any price level of a lens. Some times the lens is bad straight out of the box, some times it cannot stand up to use. One has always to keep a watchful eye to the images delivered just in case the lens no longer is up to par.

[David H. Hartman]

Lars:

I have an AF 35-70/2.8D that has a problem. The first thing I noticed was artifacts only above palm fronds after sharpening. Then when doing a quick AF fine tune check I saw smearing only above and only through the center and bottom of the frame not along the top. The problem is much reduced by 5.6 and gone by f/6.3. This defeats the purpose of an f/2.8 zoom. I'll check the cost of Repair but I think the lens is roadkill.

My advice is don't keep the lens. If several copies have a problem there may be a design flaw.

Dave

[Lars Hansen]

Thanks to everyone for the feedback.

I've spent some time considering how one should look at it in a practical perspective -  will it be visible in print size A3+/A2?  How visible is it at 50% view on screeen etc. The problem is that when you know it .. you'll probably see it. However, when watching images printed at say A3/A2 you usually watch at a distance and hopefully the image is more interesting than minor details to the left of the frame 

I've checked the camera body and the lens mount surface - I cannot detect any visible misalignments. Screws are tight and level etc. Lens seems tightly mounted and centered. I'm aware that this is not suffiecient to detect all possible misalignments - at least there are no obvious ones.   

As I wrote - the former sample I had was sent to service twice but the issue wasn't fixed so I will not try that again. It seems they don't check for such flaws despite the description from the customer. If they do shoot test charts like the ones in the LensRentals links shared by Bruno it would have been helpful to send the result to the customer - my guess is that they don't.

I will probably not be happy with it and I expect to return it. I might take it out for some extra test shots to see how it performs in average situations - i.e. not shooting brick walls etc. (.. or just a few). Out of principle, I do find it unacceptable that it's flawed out of the box and apparently it cannot be fixed when sent to service so it's not a keeper.

 

[bjornthun]

Some lenses are built with few if any means of adjusting the optics, in case of problems. Some have none, some have one, some have a few or many options for adjustments. That is, if I have understood some of the lensrental blog posts correctly. I don't know, to what extent this applies to the Fuji telezoom.

[Lars Hansen]

I've read some more on the subject - others who have experienced similar issues suggests that the OIS mechanism to some extent can be the source of misalignment due to the way it works. 

I haven't read all in the Lensrentals blogs on the subject, but it might be the case that this zoom cannot be adjusted.

I will add that I have no reservations wrt. Fujifilm's service - they have always provided a great service. Last time they offered to replace the lens but I decided to wait and give it a try later. There are no alternatives in the Fuji XF series at this price level and the reason I bought the Fuji X-E1 was due to their XF lenses.             

[Kitanikkor]

With new purchases of used lenses (my exclusive buying pattern) I always take some shots of grass/lawns to see if there's any decentering....at various apertures....an easy test...and I accept no smearing...