K5II left and right focus difference

Started Dec 22, 2012 | Discussions thread
DAVID MANZE Veteran Member • Posts: 4,631
Re: How to test for lens misalignment (decentering) - example image DA 16-45 f4


awaldram wrote:


Lenses don't fall out of corn flake packets,so when I pay £700 for the Sigma 50-150 2.8, I want a good one and believe me I will fight for it, and did!

Where on earth did you manage to pay that much for it?

Before it went out of production highest price was £499

We are paying good money and have absolutely "the right" to lenses up to spec.If you have bought a new decentered/faulty lens return it for a new one and again if necessary.

That is my point a tamron 17-50 that is uneven left to right is within spec thats how they get it to the price point they do.

I would suggest you have a look at slrgear as the only sight that maps blur index's and you'd see that only lens that are truly straight are macro lens and top end telephotos.

The middle level Sigma's/Tamrons don't get close but are better than entry level OEM's.

Most user are happy if the sharpest point hit the centre of the image, further most/all users have no concept how to test for anything else.

I say this to encourage others that you can get a good lens copy if you hang on in there!

Happy lens buying everybody

I build my own lens so have no problems re-shimming or re-aligning lens, I obviously can't fix skewed doublets but thats rarely and issue.

You may ask why I don't 'fix' my bigma.......to do so would require softening the center performance to align the far borders a price I am not will to pay. The design doesn't allow any other solution so all Bigmas have the same issue.

Most cheaper Zooms have to much tolerance in their complex mechanisms to really tune out de-centering.

You mention Klaus Photozone and I believe he has had many lens returned from service Nff once he's pronounced them de-centered.!!

Of cause if you can make enough noise to persuade a service centre to hand pick a lens for you then well done , But as I say the mechanism in cheaper lens does not support accurate lens alignment so your 'perfect' lens will not stay that way.

Alignment issue of cheap zooms is a function of their price point and so are not out of spec and are generally pretty sharp, Their decntered plane will have no affect on real images and are what get you a lens so cheap.

Prices will rise considerably if everyone wants their lens to be perfect.

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Dave's clichés

Hi again,

At the time on the net(4 years ago) the average price was around £650,inc. postage I paid £670 approx, not that this of any consequence,first copy was unacceptable,second copy was fine. No need to say anything further.

My Tamron is well centered(second copy),ie. as sharp on the left as on the right.Nothing further to say either.

BTW. The repairs took 6 weeks awaiting couplets (funnily enough)

Most people don't want to shim their lenses!

Photozone; If Klaus Schroif says a lens is decentered,it is! Whether the manufacturer agrees or not shows the state of the industry at the moment. In fact after testing the fourth copy of the Sigma 10-20 4/5.6, he added a short passage about decentered lenses and how many he comes across,with a point saying, "surely customers would not object to paying a little extra for a properly tested lens"

Sorry,  I can't go along with the "I'll just accept it as it comes" approach.

But there,we're all different!

Dave's clichés

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Dave's clichés

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