K5II left and right focus difference

Started Dec 22, 2012 | Discussions thread
DAVID MANZE Veteran Member • Posts: 4,630
Re: How to test for lens misalignment (decentering) - example image DA 16-45 f4


awaldram wrote:

Trevor G wrote:



As far as I'm concerned a decentered lens is a lens not worth keeping,lesser quality well centered lenses often produce sharper images.


There is no reason to keep one unless you bought it used and don't want to pass it off to someone else.

Unfortunately not many people know how to check, or what to look for.

The reason you hear of it more today is because of the cheap image (no processing costs) people are testing threir lens until they find a fault (real or failed test practices).

Lens manufacturer has improved in leaps and bounds over the last couple of decades with lens alignment errors getting smaller and smaller.

But people are getting higher resolution cameras so can resolve smaller and smaller errors.

hence why this sentence "As far as I'm concerned a decentered lens is a lens not worth keeping,lesser quality well centered lenses often produce sharper images." is an exercise in futility and if carried out logically , would result in no lens in your collection.!!

-- hide signature --

Hi Awaldram,

First point,yes of course it's easier to check lenses and long may it be so:

Second point,Yes, lens design has improved considerably in recent years, but I disagree that lens alignment errors are getting smaller, lens reviewers are always complaining,Photozone, see at DPreview their experiences with the Pentax K01 and associated lenses. (please respond to that point)

Third point, higher resolution "does" tax lenses to the full,which is "exactly" why we need well centered lenses!

Fourth point, Hang on to your decentered lenses if you feel happy about it!

History of lenses I have purchased in the last five years;

1:Tamron 17-50mm 2.8 first copy badly centered at 50mm,replaced/repaired,  copy V.good

2: Sigma 50-150mm 2.8 first copy badly centered at 50mm,replaced copy,  V. good

3: Sigma 10-20mm 4/5.6 first copy slightly decentered at 10mm,returned copy, V good

4: Pentax 16-45mm   first copy V.good

5: Pentax 21mm 3.2 Ltd  S/H: slightly decentered,returned to Pentax,who ruined it completely,returned again, they sent me a returned and checked lens,   V.good

6: Samyang  8mm 3.5    first copy, V good

7: Pentax 50mm 1.4      first copy, V.good

8: Carl zeiss jena 75-300mm  S/H  at least twenty years old,   V.good

9:  Sigma 18-50mm 2.8  S/H  Big mistake horribly decentered+ bad AF, as a matter of interest I shimmed one side of the bayonet and corrected it's eccentricity to a reasonable degree, it is usable on the K01 ,but it's going!

10, Pentax 18-55 WR    S/H  V good

Out of the 10 lenses, my 4 most used lenses had to be returned, these lenses cost me £1,600 ignoring the 18-50 sigma,so for that sort of dosh,I want sharp lenses that are up to spec.

Was all the hassle worth it? (returns,postage,one lost parcel,insurance etc) YES,you bet your life it was, I have now lenses that are worth having and a much nicer taste in my mouth.

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!

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.

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

Happy lens buying everybody

Dave's clichés

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