[borisbg]

Hi Dave,

 

Can you re-shoot the photo on tripod with VC off?

 

What shooter speed did you use? And did you hand hold the lens?

[davidmanze]

 First off, I can't even find the photo, it took some time to find the thread!

 

   Yes it was hand held, and I don't know if there was VC, my typical settings are 1/1250-1600 F8-11, but it changes little, I've seen this many times in similar situations although less so with the G2.

  Here it is just too hot for tele-shots at the moment!  I'll take some shots when there's some clear air!

[davidmanze]

Yes. My guess is something was in front of the soft area; very close and small so it was diffused by the time you reach the subject. If you were to go back to the location and re-shoot the image i bet the area would be gone. I do not think it is heat or atmospheric; as it is too localize.

   

    I was shooting across water, nothing in front!

[stoppingdown]

Time ago I posted some photos here with a similar problem. But at the moment I can't find that old post.

[stoppingdown]

Found:

 

http://forum.photozone.de/index.php?/top...sel70200g/

 

It seem we all agreed that OSS was most probably the culprit. I'm not sure it was the same defect, because the whole vertical strip of the image was affected.

[miro]

Hi Dave,



You already received many suggestions and possible cause of this issue.



My proposal is to exclude some of them. To do this can you please make test image in more LAB environment?



E.g. shoot flat peace of newspaper with controlled light condition – use different focal length and aperture, For calibration you can use old trusty lens with similar focal length.



Other interesting lab test is AF accuracy at different AF points.



 

Regards,

Miro

[davidmanze]

Hi Dave,



You already received many suggestions and possible cause of this issue.



My proposal is to exclude some of them. To do this can you please make test image in more LAB environment?



E.g. shoot flat peace of newspaper with controlled light condition – use different focal length and aperture, For calibration you can use old trusty lens with similar focal length.



Other interesting lab test is AF accuracy at different AF points.



 

Regards,

Miro

Hi Miro,

  I haven't the appropriate building for shooting such tests.....I live on a 9.3 mts boat.

 

 However, I will post further examples as and when I come across them, on a flat plane this effect does not show up, I think it's to do with the quailty of the Nissan bokeh at the focus transition which causes this strange softness, the outer edges are hard and highlighted and while the center of the stem is somber and transparent.

  The Tamron A011 (G1) hasn't the softest OOF rendering with onion ring bokeh as well and I noticed this patchy softness, the G2 has much softer bokeh and I see the issue less often. The Nikor AF-S suffers from Nissan bokeh in front of the plane of focus, but is soft in nature behind.

  Another weird bokeh effect is bubble bokeh, again I have the Helios 44-2 which produces the bubble effect, but the distance between the subject and the background has to be just right or the effect doesn't happen. Like moiré conditions have to be just right to see it.......(or wrong depending on your POV)!

[Brightcolours]

Hi Miro,

  I haven't the appropriate building for shooting such tests.....I live on a 9.3 mts boat.

 

 However, I will post further examples as and when I come across them, on a flat plane this effect does not show up, I think it's to do with the quailty of the Nissan bokeh 

In the good old days we marvelled in Datsun bokeh... 

[davidmanze]

    Yeah based on the old Ford model "T" stops!  :o

[Guest]

Aspheres cause there to be funky hotspots in the image, the more you add the worse things get.  E.g this happens:

http://i.imgur.com/9w7v9PV.jpg

where a lens may have little to no coma in the corner, but "a lot" of coma in the center. 

 

The tamron does not have an asphere, so that can't be the case.  The first few elements need to be made on a large diameter grinder and likewise for the polisher, which is expensive.  Lower quality machines exist, but they leave surface defects - this is probably the case.  You can actually fairly clearly see the steps in the grind/polish process as the tool or workpiece is moved and then spun (the rings in the bokeh). 

 

Such defects will hurt contrast and typically do not result in a "clear aberration" in the image, a very narrow faced edge would have to be made which is unlikely. 

 

It most likely has to do with the VC, atmospheric conditions, or subject motion.

 

Looking at the image more closely there appears to be a circle centered around that spot which is also fuzzy, so it may be something to do with a filter of some kind, a bad element inside the lens, or some other defect.

 

 

looks like Panasonic has some laborious way of getting rid of the onion rings bokeh when grinding lenses:

 

http://www.imaging-resource.com/news/201...ric-lenses

 

not sure if that is used now regularly, probably not.