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Crazy bokeh from the A 100/4 macro
Posted By: Rense, 08-05-2009, 02:42 PM

Most of the times, this lens has a pleasant bokeh.





But sometimes, it freaks....! Anybody who can explain this pattern? Specs of dust? And if so, where?





And yes, that is my own finger...
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08-05-2009, 02:56 PM   #2
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That looks like moisture to me. Was it humid or wet at all?
08-05-2009, 03:05 PM   #3
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I agree about moisture. Does it vary with aperture?
08-05-2009, 03:10 PM   #4
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Yes, there is a fen/pond in the background. But I did not mean the hexagons, that is caused by the reflections in the water i.c. with a rather small aperture (f/10). I ment the dots in the hexagons. What are they?

08-05-2009, 03:31 PM   #5
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I think it is dust or a spot on the front element, and stopping down has highlighted it
08-05-2009, 03:53 PM   #6
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I agree with Lowell that there is likely a mark one of the lens elements, I have a lens with a marked element that makes similar patterns.
08-05-2009, 04:23 PM   #7
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i kind of like this bokeh.... i've seen some offbeat postings about folks who take black paper, cut out a design in the front, slap on the front of the lens, and you get some funky design artifacts..
how did you train this creature??? i took me a while to train my dog to sit on command...
08-05-2009, 06:33 PM   #8
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Eyes?

Even the first image exhibits the hexagons albeit fainter. I think it may be reflections from the highlights on the eyes (similar shape). This is an older lens without the newer digital coatings. I have seen similar reflections with an old A70-210. Perhaps the structure of the eye provides different reflections and that is your spots. ??

08-06-2009, 01:44 AM   #9
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QuoteOriginally posted by Rense Quote
Yes, there is a fen/pond in the background. But I did not mean the hexagons, that is caused by the reflections in the water i.c. with a rather small aperture (f/10). I ment the dots in the hexagons. What are they?
The dots with circles around them are diffraction patterns cast by dust on a lens or filter I'll bet. The small f-stop used combined with the point sources of light from water droplets results in light that allows the effect to be seen.


The two hexagons in the lower right side of the last photo contain identical diffraction patterns; therefore they resulted from the same dust. The fact they appear in different locations on the photo means they must have been reflected more than once at some distance from the sensor (if due only to dust on the hot mirror they could not be separated so far on the sensor, nor be so large compared to the hexagonal image of the aperture I think.)

Dave in Iowa

PS it is possible that specular reflections from the insect's individual hexagonal eye facets are involved. Does your lens' aperture have six leaves?

Last edited by newarts; 08-06-2009 at 01:55 AM.
08-06-2009, 06:17 AM   #10
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Thank you all, I guess you're right about dust somewhere remote from the sensor....
08-06-2009, 06:37 AM   #11
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Sure thing about dust affecting the bokeh here, but what did you do to the wings of this poor insect Rense?!?
08-06-2009, 06:42 AM   #12
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thats cool, why they don't run away ? how you did it?
08-06-2009, 08:14 AM   #13
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QuoteOriginally posted by Ash Quote
Sure thing about dust affecting the bokeh here, but what did you do to the wings of this poor insect Rense?!?
I had to do something to let him sit still

No, it's a very fresh specimen, who just saw life as adult. The feins of his wings are not yet filled with air, so they look like they have to be ironed,

QuoteOriginally posted by adriano210 Quote
thats cool, why they don't run away ? how you did it?
... and that is the reason he did not fly away, but waited calmly until I shot my photos
08-06-2009, 12:27 PM   #14
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Did you name him??
08-07-2009, 08:02 AM   #15
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QuoteOriginally posted by Wildnsyko Quote
Did you name him??
Nope. Did not think of that
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