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05-22-2018, 02:33 PM   #1
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DFA 24-70 bokeh weirdness

Hi folks

I think this is what was touched on in the PF review as "reported but we didn't see any". Not the easiest of subjects (I managed to blow the highlights in the grass), and would probably only be apparent when pixel peeping or doing a humongous print. This was at 58mm f/2.8, another shot at 48mm f/4 a moment before shows very minor effects, but only because I know what to look for.

So, the overall image:


and as big a 100% crop as I can upload:


Note (a) many little bubbles with central bright dots, (b) similar linear features at the bottom left from brightly-lit branches in the distance, and (c) astonishing weird swirly patterns at the right, presumably as a result of both foreground and background being out of focus.

Has anyone else seen examples of this, and if so do you find that it's also focal-length dependent, or just aperture?

Cheers

Jonathan

05-22-2018, 03:05 PM   #2
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These are specular highlights. Different lenses handle these differently. My old Super-Tak 55 /1.8 would blow this image up into a cacaphony of bubble bokeh which some love ajd others detest. Looks like your 24-70 has its own particular rendering. Learn to embrace it and you will he happy.
05-22-2018, 03:19 PM   #3
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You have a very high contrast scene and your 100% crop shows it is not only the grass that is blown. The purple OOF flowers look like they are suffering from flare, maybe this is contributing to the "swirly patterns.
05-22-2018, 06:42 PM - 1 Like   #4
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Just to be sure: you don't have any filters attached, do you?

05-22-2018, 07:35 PM   #5
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There was another thread on this yesterday or two days ago, I believe.

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05-23-2018, 02:11 PM   #6
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Thanks folks.

Interestingly, I found a very similar-looking effect in the review of the HD Pentax-DA 40mm F2.8 Limited. Yes, I did have a filter fitted, but I'd venture there wasn't one on the 40mm! So, maybe longitudinal CA causing axial colour? I'll have to try a few more variations when I'm next there, at differing settings and without the filter, assuming it's a sunny day. Won't be as pretty without the azaleas and wisteria, though

Time to hunt down the "other thread" of which Adam speaks...

Cheers

Jonathan
05-23-2018, 02:37 PM   #7
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QuoteOriginally posted by Adam Quote
There was another thread on this yesterday or two days ago, I believe.
Probably mine;
Circular bokeh with 24-70mm? - PentaxForums.com

05-23-2018, 03:28 PM   #8
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QuoteOriginally posted by h4yn0nnym0u5e Quote
Yes, I did have a filter fitted, but I'd venture there wasn't one on the 40mm!
I had very strange striation effects in the bokeh on the DA 55-300 a few years ago, which I eventually tracked down to a UV filter I had on it permanently. I have now taken them off all my lenses, including the DA 40 Ltd, though none of the others seemed to cause any issues. It can just be a bad filter.

05-24-2018, 01:51 PM   #9
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QuoteOriginally posted by amoringello Quote
Looks plausible! You appear only to have got the bubbles, not the central dot, though.

QuoteOriginally posted by Paul the Sunman Quote
I had very strange striation effects in the bokeh on the DA 55-300 a few years ago, which I eventually tracked down to a UV filter I had on it permanently. I have now taken them off all my lenses, including the DA 40 Ltd, though none of the others seemed to cause any issues. It can just be a bad filter.
Yes, I'll definitely try without the filter, when I have a chance to do a bit of investigation.

Thanks again folks - looks like it's nothing to worry about, just to watch out for if the conditions may provoke it.
06-01-2018, 03:53 PM   #10
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QuoteOriginally posted by h4yn0nnym0u5e Quote
Looks plausible! You appear only to have got the bubbles, not the central dot, though.
Yeah, that is strange. There is only certain photos with certain light that seems to cause the effect.
It would be interesting if the filter or something else is making the effect on yours different. Or if it is a quality/consistency control issue between lenses.

I shoot dog photos, mainly, and only sometimes does the nose reflect this way.

A lot merely down res'd to jpegs for Facebook and the issue isn't usually noticeable.
I will feel ill if I have to blow one of those up to 30x40 for a customer.
Although honestly, I don't know if most non-photographers would even notice.
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