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Archive 2017 · Nokton 40 1.2 Black Blobs in Bokeh

  
 
Sjredo
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p.2 #1 · p.2 #1 · Nokton 40 1.2 Black Blobs in Bokeh


realVivek wrote:
I think it is a manifestation of coma. Product defect?!

OMG!


If it were in fact a manifestation of coma... shouldn't it go away by F4/5.6/8?

I'll do my best to try it out tonight.



Nov 15, 2017 at 02:01 PM
Fred Miranda
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p.2 #2 · p.2 #2 · Nokton 40 1.2 Black Blobs in Bokeh


Sjredo wrote:
If it were in fact a manifestation of coma... shouldn't it go away by F4/5.6/8?

I'll do my best to try it out tonight.


If it's related to coma, it should go away as we step down.

When I tested for coma, it was pretty much free of this aberration after f/2.5.
https://www.fredmiranda.com/forum/topic/1512530/1#14214257



Nov 15, 2017 at 02:03 PM
sebbe
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p.2 #3 · p.2 #3 · Nokton 40 1.2 Black Blobs in Bokeh


Sjredo wrote:
Thanks so much Fred!!

Has anyone contacted Voigtlander about this? I can't because I don't have the invoice with me... Is this really normal?is it a production defect? or is it just something with really fast lenses?

Thanks everyone!


It looks like it is only visible with weak lightsources and f1.2. The black dot is always away from the center of the picture and goes off into the heavy coma toward the corners. Therefore you can see it the best in the center of the image.
It think it has also to do something with the mix of axial CA and spherochromatism this lens shows a very fast apertures. I'm quite sure you will not see it after f2.8.

Edit: Ah, Fred was faster.




Nov 15, 2017 at 02:06 PM
Sjredo
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p.2 #4 · p.2 #4 · Nokton 40 1.2 Black Blobs in Bokeh


Same here. It just seems to be with far away strong light sources when the focus on the subject is mid distance. I've yet to see another situation where it happens.

I hope someone can reach voigtlander or cameraquest regarding this to see if they're aware.



Nov 15, 2017 at 02:09 PM
freaklikeme
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p.2 #5 · p.2 #5 · Nokton 40 1.2 Black Blobs in Bokeh


I thought that was the effect of an inexpensive molding and polishing process on the aspheric surface.


Nov 15, 2017 at 07:24 PM
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