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70-200 VR II spot/minicrack inside on the lens element
#1
Hi, I´ve just got my new 70-200 VR II and put it to some "regular" testing to check centering quality, BF/FF etc. What I can say my 70-200 copy is supersharp, very well centered and focuses perfectly. However, what disturbs me is a kind of mini crack or spot inside the lens close to the optical axis - please see the attachment. Well, in reality the spot is even not that big as shown in the pic (it is blurry on the pic because I cant get my compact cam to focus properly in the macro mode) but it definitely doesn´t look like a common dust particle. In all probability, it is a lens defect.



Do you think it may somewhat influence the optical performance of the lens when it is not directly in the optical axis or am I doing too much ado about nothing...?! That means (another Shakespeare quote) return the lens for a new copy or not return the lens...? I´m saying again the spot is even smaller in reality (with sharp edges) than being shown in the pic... Moreover, it is normally not that visible, I put the light source in a very specific angle to make it as visible as possible... But it is there...
#2
sorry, here is the attachment...
#3
It certainly does not look like a "crack", and this unfocussed I can't see if it is an air bubble or something else. Nor can I judge the size of the irregularity. If it is a bubble in a glass element, no need what so ever to worry. In the past, small bubbles in lenses actually where a sign of the high quality of the used optical glass, and as such were seen as an attribute of the high quality of the optics of a lens.



Such a bubble has no impact on the optics and following image quality, so you should have nothing to worry about. And since you find it to be super sharp and centered perfectly, just use the fine optical instrument!
#4
[quote name='Brightcolours' timestamp='1323179758' post='13485']

It certainly does not look like a "crack", and this unfocussed I can't see if it is an air bubble or something else. Nor can I judge the size of the irregularity. If it is a bubble in a glass element, no need what so ever to worry. In the past, small bubbles in lenses actually where a sign of the high quality of the used optical glass, and as such were seen as an attribute of the high quality of the optics of a lens.



Such a bubble has no impact on the optics and following image quality, so you should have nothing to worry about. And since you find it to be super sharp and centered perfectly, just use the fine optical instrument!

[/quote]





Actually it looks more like a very small bite or minicrack in the lens element... Or, like a "glass speckle" processed in the lens element, if you want... Do you think it can somewhat appear on / influence the resulting image?
#5
[quote name='Martin_MM' timestamp='1323182684' post='13487']

Actually it looks more like a very small bite or minicrack in the lens element... Or, like a "glass speckle" processed in the lens element, if you want... Do you think it can somewhat appear on / influence the resulting image?

[/quote]

I don't think it can.
#6
[quote name='Brightcolours' timestamp='1323182966' post='13488']

I don't think it can.

[/quote]



OK, thank you.



I´m still judging the replacement just for the sake of "perfection", though.... Like if you buy a new car with a scratch on the paint - it doesn´t have an influence on its riding performance either but still you probably wouldn´t like it there much, too...





I wonder what is Klaus or Marcus´s opinion on that - hey, guy, r u there? ;-)
#7
[quote name='Martin_MM' timestamp='1323186981' post='13490']

I wonder what is Klaus or Marcus´s opinion on that - hey, guy, r u there? ;-)

[/quote]



Yep, right here <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Smile' />



Well, if this is a new lens, I'd find it a bit disappointing myself, for sure. If the lens is still under warranty, you might consider to have it cleaned by service (if the lens performs well I'd personally prefer that over a replacement).



However: that small particle won't have any visible influence on your images. In addition, if you use the lens well and often, it will soon be joined by quite a few dust particles (which you may also need special light to spot). It would takes loads of dust spots to have a visible influence on the image quality of the lens.



So, if your concerns are mainly about image quality: don't worry, be happy (not Shakespeare, sorry).



-- Markus
Editor
opticallimits.com

#8
[quote name='mst' timestamp='1323193792' post='13492']

Yep, right here <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Smile' />



Well, if this is a new lens, I'd find it a bit disappointing myself, for sure. If the lens is still under warranty, you might consider to have it cleaned by service (if the lens performs well I'd personally prefer that over a replacement).



However: that small particle won't have any visible influence on your images. In addition, if you use the lens well and often, it will soon be joined by quite a few dust particles (which you may also need special light to spot). It would takes loads of dust spots to have a visible influence on the image quality of the lens.



So, if your concerns are mainly about image quality: don't worry, be happy (not Shakespeare, sorry).



-- Markus

[/quote]





Hi, thank you for your reply.



OK, I would rather have it cleaned by service...but like I said, the 'problem' is it doesn´t seem to be a dust particle - it seems like a small bite or minicrack in the lens element... Or, like a "glass speckle" processed in the lens element....



You are kind of a lens expert with lots of experience - please is it really risky to exchange this Nikon 70-200 VR II lens for another copy in terms of sample variations..? I would be worried with the 3rd party manufacturers, however, I hear esp. Nikon quality control in the Pro line lenses is rather high...(?)
#9
If you suspect it is something actually in the glass (not something that can be wiped away), than a replacement might be the better idea. If it's something in the glass, that element (or several) might need to be exchanged and who knows how the performance/centering will be afterwards. Once it has been to service, replacing the whole lens might no longer be a valid option...



I haven't heard of significant sample variation regarding the 70-200 VR II. However, whatever lens and whatever brand, you'll have to check any individual lens anyway. Even if the risk to get a lemon is low, it's still a risk...



-- Markus
Editor
opticallimits.com

#10
[quote name='mst' timestamp='1323201052' post='13494']

If you suspect it is something actually in the glass (not something that can be wiped away), than a replacement might be the better idea. If it's something in the glass, that element (or several) might need to be exchanged and who knows how the performance/centering will be afterwards. Once it has been to service, replacing the whole lens might no longer be a valid option...



I haven't heard of significant sample variation regarding the 70-200 VR II. However, whatever lens and whatever brand, you'll have to check any individual lens anyway. Even if the risk to get a lemon is low, it's still a risk...



-- Markus

[/quote]



OK, you are right - thank you. The lens will go back.



BTW, does the de-centering test (the template) Klaus posted here http://forum.photozone.de/index.php?/top...nity-check work correctly when printed on A4 paper and shot with a lens from say 1.5m? (which is MFD of the 70-200 anyway...).
  


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