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Author Topic: Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM  (Read 11298 times)

kshuler

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« on: April 30, 2008, 01:23:09 am »

Hello-

I just bought a Sony (Zeiss) vario-sonnar 24-70mm f/2.8 ZA SSM lens and have been putting it through the ringer to see if I have a good sample or not.  It is awful sharp even wide open, but my questions concern the bokeh of the lens.  Now, I bought it mostly for landscape use, so Bokeh was not my primary concern, however, I find myself using it around the house for portraits and documenting the growth of my children more than for landscapes, and for this reason I DO care about the bokeh.

I have seen reviews out there that show pretty decent bokeh with the lens.  But pretty much all of those reviews are close up pictures with distant backgrounds, minimal specular highlights, etc.  I can get good bokeh out of a mirror lens if I choose the background right.  My real world shooting situations are usually NOT taking pictures from 2 feet away, but from around 15 feet away, and not watching the background so carefully, but just trying to get my kids doing whatever they are doing that i think is worthwhile taking a picture of (by the number of pictures I take of them you would think I want to document every breath).  The problem is this- when I shoot the occasional closeup I get nice bokeh in the background.  When I shoot at 5-15 feet, I often get horrible rings of light as if I was shooting with a mirror lens.  But not reliably so.  I have even gone back to the same location to shoot the same scene again to confirm the bad bokeh and had fairly neutral bokeh the second time around.  My point is, I don't get it.  And I don't have any examples out there to compare to, other than the closeup shots on the web.  But as I say, my closeup shots look fine, too.

I will attach 2 pictures to the message to show you what I mean-- 100% crops of bakground images.  If the attachments don't work, here are the links:

http://www.bokehtests.com/temp/SAL2470ZAbokehcloseup.jpg
http://www.bokehtests.com/temp/SAL2470bokehclose.jpg

[attachment=6339:attachment]
[attachment=6340:attachment]

Does anybody out there have this lens?  Does anybody else have any issues with bokeh at medium focal distances?  Can anyone post any pictures of bokeh in difficult conditions at medium focal lengths?  If so I would appreciate it.  I don't know if I got a bum copy of this lens, or if this is just the way it is in all samples.

I have also started the formal testing of bokeh on this lens.  It is the first one that i have done so in any kind of scientific way, but it is very labor intensive and time consuming.  For those interested, there seems to be a bokeh sweet spot in the center of the lens at a focal range of 5-10 feet and f/2.8 aperture, but the 10 foot focal length has HORRIBLE bokeh at the edge of the lens.  Anyone interested can see the initial results (about half of what is needed on the 70 mm side, still have to do 50mm and 24 mm) of the testing at the following link:


http://www.bokehtests.com/Site/Sony_Zeiss_24-70_Bokeh.html

Anyway, I would appreciate any help you might have for me.  I have 30 days to return the lens, but I bought it on the 8th of April... need to decide SOON.

THank you all!

Klaus
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http://www.bokehtests.com
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01af

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« Reply #1 on: April 30, 2008, 08:49:08 am »

When bokeh is important then do not use the lens wide open. Stop it down one f-stop, or at least a half. With most lenses, this will improve bokeh considerably.

-- Olaf
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kshuler

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« Reply #2 on: April 30, 2008, 12:31:07 pm »

Quote
When bokeh is important then do not use the lens wide open. Stop it down one f-stop, or at least a half. With most lenses, this will improve bokeh considerably.

-- Olaf
[{POST_SNAPBACK}][/a]


Hi Olaf,

THanks for responding.  The pics I took were at f/3.5, 2/3 stop down from wide open, hoping that this would improve the bokeh and sharpness a little.  But clearly they did not.  And looking at the tests I did on my website (http://www.bokehtests.com/Site/Sony_Zeiss_24-70_Bokeh.html) you can see that, oddly enough, bokeh seems to get noticeably harsher as you stop down more.  Is this a quirk of the lens design or just a bad copy of the lens?

Klaus
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[a href=\"http://www.bokehtests.com]http://www.bokehtests.com[/url]
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douglasf13

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« Reply #3 on: April 30, 2008, 01:25:02 pm »

Quote
Hi Olaf,

THanks for responding.  The pics I took were at f/3.5, 2/3 stop down from wide open, hoping that this would improve the bokeh and sharpness a little.  But clearly they did not.  And looking at the tests I did on my website (http://www.bokehtests.com/Site/Sony_Zeiss_24-70_Bokeh.html) you can see that, oddly enough, bokeh seems to get noticeably harsher as you stop down more.  Is this a quirk of the lens design or just a bad copy of the lens?

Klaus
--
http://www.bokehtests.com
[a href=\"index.php?act=findpost&pid=192696\"][{POST_SNAPBACK}][/a]


  I have had the lens for over two months, and I haven't had this problem.  I just tried to duplicate it today as well, but had no luck.  Maybe a bad lens???
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kshuler

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« Reply #4 on: April 30, 2008, 03:21:05 pm »

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I have had the lens for over two months, and I haven't had this problem.  I just tried to duplicate it today as well, but had no luck.  Maybe a bad lens???
[{POST_SNAPBACK}][/a]


Just ran outside to do some more tests to show how aperture affects this:

These are at f/2.8
[attachment=6348:attachment]
[attachment=6349:attachment]

Here is f/4:
[attachment=6350:attachment]

And finally here is f/5.6
[attachment=6351:attachment]

As you can see, by f/5.6 this goes away, but only at the expense of ring artifacts now in BOTH the center and the edge.  Not exactly the cure I want.

If nobody else can repeat this, then I have to exchange the lens.  Let me know what you think.  Thanks!

Klaus
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[a href=\"http://www.bokehtests.com]http://www.bokehtests.com[/url]
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douglasf13

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« Reply #5 on: April 30, 2008, 03:56:52 pm »

I have two things.  

First is:  Make sure you're not focusing past the infinity mark if you're using manual focus.  In manual focus, the lens goes a bit past infinity, and if you say your focus distance is about 15 feet, that sounds like it's close to being past infinity focus.

Second is: make sure you're not using a UV filter for the test.  I've seen weird bokeh things happen with UV filters before, even though it's rare.

Good luck!
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Yakim Peled

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« Reply #6 on: December 17, 2008, 02:36:29 am »

IMHO such bokeh performance is simply inexcusable on such an expensive lens. Unfortunately, there is no other alternative that offers 2.8, SSM and such zoom range in the Sony lens range. You either have to live with this or give up one of these traits. If it was me I'd go for the latter option.

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Happy shooting,
Yakim.

douglasf13

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« Reply #7 on: December 17, 2008, 04:25:34 am »

I own this lens, and I get the same bokeh in some instances.  It is the nature of the beast.
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kshuler

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Bokeh on Sony Zeiss 24-70 f/2.8 ZA SSM
« Reply #8 on: December 17, 2008, 08:01:04 pm »

Yes, I have just learned to deal with the less than perfect bokeh from this lens.  It isn't bad when focussed very close, though.  I usually use the 70-200 ssm for portrait shots nowadays anyways, and that seems to have considerably better bokeh.  Haven't gone about formally testing it, yet, though.  Seriously toying with the idea of buying the 135 STF... but then again, the Zeiss 135 1.8 is also so appealing, also with apparently good bokeh (not like the STF but definitely acceptable).  Not sure of the two which would be best.  From Photozone, they appear almost exactly as sharp, with speed an autofocus advantage to the Zeiss and Bokeh advatage to the STF.  That is a VERY difficult call for me.

Klaus
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http://www.bokehtests.com
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