[stoppingdown]

The picture above is a 1:1 crop from the _central_ area of a photo taken with the A6000+SEL70200G (the shoot details are in the image). The lens is a very sharp one and all the branches in the photo, both at the left and the right of this section, are quite sharp (up to the borders of the photo). It's even not a DoF thing, since _all_ the branches in a larger tree at the left are sharp.

 

It's not a problem that ruins the photo, but I just don't understand which effect can cause blurriness in a limited, central section of a photo. 

 

PS It might be motion blur, in the sense that perhaps the branches were moving. But, apart the fact that I don't recall there was a wind strong enough to move naked branches, what's about all the other branches that are perfectly still?

 

Thanks.

 

[ATTACHMENT NOT FOUND]

[Scythels]

Everything in that "strip" of the image is bad.  Not sure why - may be some strong astigmatism in the center due to the asphere being mis-aligned but I doubt it. 

[stoppingdown]

Everything in that "strip" of the image is bad.  Not sure why - may be some strong astigmatism in the center due to the asphere being mis-aligned but I doubt it. 

 

Could be due to the OSS? BTW, I took several shots with slightly different framing, and the others are fine.

[Scythels]

Could very well be the OSS, really it probably is.  With only spherical lenses and in a perfectly aligned system astigmatism is forbidden in the middle of the picture.  OSS introduces voluntary decenters.  For prime lens design they are relatively easy to design with because the beam of light is fixed.  In zoom design they are difficult to work with because the beam will "walk" between the different zoom positions so the effect of the asphere changes.  Add in OSS and you add a second layer of beam walk.  If the OSS group's motion is not perfectly constrained to one axis it's likely that the decenter interacts badly with the system and introduces astigmatism (which is what this looks like it is).

[soLong]

....oops....here again, sorry....just looking at the picture on this iPad thingy - don't all the out of focus bits have a double image to them, hmmm....yes they do on my 'puter and nec screen too.....not good, so sorry - but it has to be very calm on my camera at that speed, and then i think i’m lucky if branches haven’t moved

[davidmanze]

If the others are fine it could be the OS starting up as the background is also soft in that middle area!

[popo]

Just to throw in a more wild idea: moving air? I don't know what distances or other environmental conditions were, but I have found moving air (e.g. local heating from sunlight) can cause degradation in more distant objects very easily.

[stoppingdown]

I thought about moving air too... it's quite common in landscape with warm air (BTW, it was not warm, about 3-4°C - but I think we can have turbulence even with cold air and full sun).

 

But... just in such a small part of the image? Furthermore, in all cases of moving air that I'm experienced with I see a sort of twist effect, while branches, while blurred, are still "straight".

[dave9t5]

I thought about moving air too... it's quite common in landscape with warm air (BTW, it was not warm, about 3-4°C - but I think we can have turbulence even with cold air and full sun).

 

But... just in such a small part of the image? Furthermore, in all cases of moving air that I'm experienced with I see a sort of twist effect, while branches, while blurred, are still "straight".

 

I'm seeing blur all the way to infinity in that streak.  But...there is a double image in one of the trees as well.   If not for the double image, I might suggest to check if there is a small smudge on the rear element (which might account for such a localized blur).

[Klaus]

I'd also bet on the OSS here.