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Do-it-yourself centering sanity check


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#21 stoppingdown

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Posted 09 November 2013 - 02:16 PM

I just ran the test on my just arrived Sony 4/10-18mm... Former attachment is focused, latter is slightly defocused. It has been taken according to the suggestions, but I didn't use the tripod: I think it's ok because the lens is stabilised. The focused image doesn't look decentered, or at least too much; the defocused image looks it is. Your opinion?

 

Now, the practical question. I've bought through Amazon and I think they shouldn't contest a return because of a defect, and send me a replacement. But how many chances I have that the new lens is better (above all, how many chances about one which is worse)? I mean, if my current sample is just slightly decentered, is it worth while asking for a replacement? Does somebody have some experience about how many times Amazon would satisfy a replacement request? Thanks.

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stoppingdown.net

 

Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm ƒ/5-6.3 DG OS HSM Contemporary, Samyang 12mm ƒ/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm ƒ/2.8, Samyang 8mm ƒ/3.5 fish-eye II
Plus some legacy Nikkor lenses.

#22 Klaus

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Posted 28 December 2013 - 09:28 AM

It's probably too late but if this lens was mine I would return it for sure.


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#23 stoppingdown

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Posted 28 December 2013 - 09:55 AM

Not too late, as I contacted Sony right after my latest post here and they asked for a proof... I'm just waiting for a LED panel to redo all the chart tests in decent light conditions.


stoppingdown.net

 

Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm ƒ/5-6.3 DG OS HSM Contemporary, Samyang 12mm ƒ/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm ƒ/2.8, Samyang 8mm ƒ/3.5 fish-eye II
Plus some legacy Nikkor lenses.

#24 josa

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Posted 17 February 2014 - 12:00 PM

Hi Klaus, if I prit the template on A4 and put it on the wall, tak the picture, will result be the same? Thanks.



#25 mst

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Posted 17 February 2014 - 04:00 PM

The resolution of the template might not be sufficient to give really sharp edges in an A4 print. However, you may give it a try.

On the other hand, it should be quite simple to create a similar pattern with a vector drawing program, which you can then scale to any size wanted.

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#26 josa

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Posted 17 February 2014 - 07:26 PM

Thanks Markus!



#27 casual snapper

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Posted 17 February 2014 - 09:47 PM

Hello from Germany! :)

 

After some tests I managed to do a test with both planes in parallel with my brand new Fuji X-E1 & XF 18-55.

Result: I am able to focus to a point, where all four lines are almost equal, however a slight defocussing shows a rather worrysome result. Both are 100% crops from the center. Unfortunately I don't have a second lens for comparison. Hmm, what should I do?

 

- Frank

 

Attached Files

  • Attached File  2.jpg   5.36KB   30 downloads
  • Attached File  1.jpg   5.08KB   30 downloads


#28 Doroga

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Posted 18 February 2014 - 05:12 PM

To everyone:
I had Sony SEL50 sample which passed this test perfectly but one corner was rather bad.
Be sure to check if all corners have same quality/resolution even if this test shows no issues.

Frank:
If you can exchange this lens with no question asked - just do it.
Getting some pictures that clearly show sharpness issues (like weak side/corner) should be helpful in most other cases.



#29 casual snapper

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Posted 21 February 2014 - 04:36 PM

Hi everyone,

 

what about the testing of the edges?

Focussing with the center AF-field on a distant object (approx. 100m) in maximum
wide angle setting and ma. aperture, then switching to MF and comparing how much the four edges
are out of focus in relation to each other (not absolutely).

 

How ist the accuracy and importance of this test compared to the "5 checkerboard" test?

 

- Frank

 

Edit 2 March 2014: I was able to exchange the lens. In fact I got two successive replacements. The checkerboard test was ok with both, however both showed unevenly sharp edges at wide setting. I kept the 2nd replacement, because I noticed the problem was a slightly inclined field, with could easily be compensated by a minimal refocussing or inclination of the camera and is almost not relevant in real world situations.

However, sad enough, I had three XF 18-55 and not one of them was ok in both tests.

By the way, my newly acquired XF 35 mm performs fine with both tests.



#30 TomPhillpotts

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Posted 20 November 2014 - 02:50 AM

Hi all,

 

I seem to have the same problem, I'd like to get some other's opinions on this. 

 

I have a Fuji XF 18-55, here's the results of my test. I think the problem is there, but perhaps not as serious as Frank's above, for example?

 

My question is, is this problem bad enough to be worth me exchanging the lens for another, considering that the replacement lens may be worse than what I have now?

 

Thanks for your input.

 

Tom

 

Attached File  XE2F1885 Focus.jpg   186.04KB   1 downloadsAttached File  XE2F1888 Defocus.jpg   191.8KB   1 downloads



#31 Klaus

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Posted 20 November 2014 - 09:48 AM

Well, there is a margin of error that you have to accept.

The first image indicates that full focus is achieved - plus/minus a little.

It is not a perfectly centered lens though.

I am not sure whether Fuji would replace a lens like this.

Looking at the characteristic of the blur I would check the lower right corner for asymmetry vs the others (in real life images).


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#32 TomPhillpotts

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Posted 20 November 2014 - 11:48 AM

Thanks for your feedback, that's a relief to hear.

 

A cursory look through some shots seems to indicate no apparent asymmetry among the four corners. They all seem to match up.

 

If you're not sure Fuji would replace it then that's fine by me. I'm happy to accept this, as it doesn't seem to be affecting my shots. I'm glad it's within the margin of error and I needn't go through the bother of exchanging it and the potential saga that may ensue.  

 

Excuse me now, I have to go and take some photos  ^_^



#33 dave's clichés

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Posted 20 November 2014 - 10:29 PM

Well in fact I'm a Pentax user and it seems that I cannot do this test, however I use infinity focus on distant views of landscapes/trees to ascertain whether a lens is decentered, shot wide open at all focal lengths, it has never let me down so far!



#34 Klaus

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Posted 21 November 2014 - 12:39 PM

Well, you can do the test. Just take a shot with AF and then switch to MF, defocus slightly and take another shot. Then compare. That's assuming you don't have live-view.


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#35 borisbg

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Posted 21 November 2014 - 07:55 PM

To: PZ crew,

 

Is it possible to create file with above pattern and instructions, available for download to PZ members?



#36 borisbg

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Posted 21 November 2014 - 07:57 PM

It's probably too late but if this lens was mine I would return it for sure.

Klaus, how did you determine this? My eyes are not as well trained as yours.



#37 Klaus

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Posted 22 November 2014 - 12:39 PM

Well, these are CENTER images (referring to the December samples by stoppingdown).

In the center these edges should have an absolutely symmetrical sharpness (it's different in towards the borders). 

The left and bottom edge transitions are sharper than the top and right ones.

This is more apparent in the slightly defocused image but in this case this is also just visible in the focused one.

Please note that if this is already visible in the center, it'll just be worse in one of the corners or sides.


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#38 borisbg

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Posted 23 November 2014 - 09:37 PM

Now that you said it I see the difference. So it has to be really really perfect in the center.

#39 Bghead8che

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Posted 06 December 2015 - 12:49 AM

Am I understanding the distance correctly?  For a standard 50mm prime I would need to be at least 9.8 feet away, correct?  Obviously the image only fills a small portion of the frame at that distance.

 

I also would like to test an 85mm prime I have but I can only get 9 feet back without hitting the wall.  Do I really need to be over 16.7 feet away?  That would mean I would need to move my computer and use a hallway.

 

How important is distance?

 

Thanks!

 

-Brian



#40 you2

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Posted 06 December 2015 - 02:19 PM

Where do we get a copy of the image ? If I download quad.jpg in first post it is pretty small on my monitor. I'll be posting my test results soon (I hope I am not too unhappy).






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