# Strange artifact in OOF area



## Maximilian (Mar 23, 2015)

Hi to all artifact specialists! 

I have a problem identifying a strange artifact in the OOF area of the following picture of a lynx. 
I have attached a detail of the affected area in higher resolution. 

If you can tell me where it comes from please let me know. Thank you very much in advance.

Detail information for this picture:
Lynx at the zoo shot through a fence with vertical and horizontal straight bars, fence about 1 m away.
I am 90% sure that I managed to get the shot through the hole of the mesh.
There was only a light breeze an I cannot recall if branches were moving or not.

Further data:
5D3, 100-400L, @400mm, 1/400, 1/6.3, ISO800, Tv, AI servo, IS on at mode 1, no cropping


_edit (what I wanted but forgot to mention):_
Lens hood was on, high quality multi coated UV filter (as protection) was on, time was 11.30, I was pointing east, so sun light came almost 90° (horizontal) from the top right, no water, glas, tin etc. to produce reflections.


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## neuroanatomist (Mar 23, 2015)

Assuming you're using the MkI lens, it ooks like the 'jittery bokeh' that's a hallmark of the 100-400L.


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## Maximilian (Mar 23, 2015)

I posted a second picture from the same visit without any issues here 
http://www.canonrumors.com/forum/index.php?topic=25648.msg505955#msg505955


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## IMG_0001 (Mar 23, 2015)

Were you using the hood and/or a filter?

To me the arcs look like they are the reflections of something either outside or inside the lens. The rightmost one, particularly, is very regular and does not look like its out of focus. then, it looks like the leftmost one is somewhat symmetrical and the pattern kind of repeats itself. It would almost look like if the front of the lens was reflected from the inside of a filter. If these are indeed reflections, the fact that the artifacts disappear behind the cat is somewhat strange however.

Well that would be my guess...


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## Maximilian (Mar 23, 2015)

IMG_0001 said:


> Were you using the hood and/or a filter?


Thank you for your suggestion, IMG_0001.

Please see additions in the OP answering your questions. 
Please also note the other picture I took from (almost) the same position to the same target (see stone the lynx is sitting on). Little bit different angle though.
Maybe the additional information will lead you further on.
I've got something in mind, but don't want to tell yet.


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## Maximilian (Mar 23, 2015)

neuroanatomist said:


> Assuming you're using the MkI lens, it ooks like the 'jittery bokeh' that's a hallmark of the 100-400L.


Yes! It's the MKI. but I never realized something that big in any of my pictures. That's why I'm puzzeled.

But thank you, Neuro. Maybe it's time to save up (faster) for the MkII.


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## Joe M (Mar 23, 2015)

Yes, it's simply the oof branches back there that didn't go buttery smooth. Luckily there are only a few and for me it's not enough of a distraction from the beautiful animal. I hope it's not too forward if I suggest that in this case, a slight bit of manipulation in photoshop can easily get rid of the minor irritation if you so wish. And nice capture on the other shot too.


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## Maximilian (Mar 23, 2015)

Hi Joe! 

First of all I agree that this is nothing serious and it can be handeled in post. 
But I try to avoid such things if possible.



Joe M said:


> Yes, it's simply the oof branches back there that didn't go buttery smooth.


Of course that was the first thing that came to my mind. But the right part looks so geometrically round that I couldn't believe in any kind of oof branch.



> Luckily there are only a few and for me it's not enough of a distraction from the beautiful animal. I hope it's not too forward if I suggest that in this case, a slight bit of manipulation in photoshop can easily get rid of the minor irritation if you so wish. And nice capture on the other shot too.


Thank you for your compliments and of course you are right, that this is nothing one can't handle in post.


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## IMG_0001 (Mar 23, 2015)

Light coming at a high angle has more chance of being reflected than if coming from straight on. The fact you would have the sun coming at a steep angle (although you used a lens hood) combined with the fact you were using a filter, would actually lead me to believe in the possibility of internal reflections.



Maximilian said:


> IMG_0001 said:
> 
> 
> > Were you using the hood and/or a filter?
> ...



I really do find the artifacts to be quite symmetrical and also quite well defined (particularly the rightmost ones) to be oof branches rendering poorly...



Joe M said:


> Yes, it's simply the oof branches back there that didn't go buttery smooth. Luckily there are only a few and for me it's not enough of a distraction from the beautiful animal. I hope it's not too forward if I suggest that in this case, a slight bit of manipulation in photoshop can easily get rid of the minor irritation if you so wish. And nice capture on the other shot too.



And finally, surely not something moving as 1/400 should stop most moving twig action I guess...


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## Bennymiata (Mar 23, 2015)

That's the reason I don't use UV filters.


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## zim (Mar 24, 2015)

What colour and thickness were the (I assume) round wires of the mesh?
I'm thinking specular reflection off of a shiny bit onto the filter/front element, a tiny movement or the sun dulling slightly would make that disappear


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## neuroanatomist (Mar 24, 2015)

It's a combination of selected aperture, focus distance, and subject-to-background distance. Certain lenses are more prone to this poor OOF rendering ('jittery' or 'nervous' bokeh), the 100-400L being one of them (the MkI, at any rate - not sure about the MkII). A couple of examples are shown below. 



Bennymiata said:


> That's the reason I don't use UV filters.



A front filter is not the cause. Reflections from the rear surface of a front filter would manifest as reduced contrast (and thus the appearance of reduced sharpness) across the entire image, as a result of veiling glare, not visible reflections of specific elements in OOF areas.


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## neuroanatomist (Mar 24, 2015)

zim said:


> What colour and thickness were the (I assume) round wires of the mesh?
> I'm thinking specular reflection off of a shiny bit onto the filter/front element, a tiny movement or the sun dulling slightly would make that disappear



Ahhh, when I first viewed the images it was on my phone, and I presumed the artifact was the general appearance of the bokeh. Viewing the images on the computer, I see what the OP is talking about. 

It may, indeed, be a result of the wires of the enclosure causing a weak flare artifact.


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## TeT (Mar 24, 2015)

neuroanatomist said:


> zim said:
> 
> 
> > What colour and thickness were the (I assume) round wires of the mesh?
> ...



I think it is in the BOKEH. The leftmost downward slash of the artifact ends at the body of the cat where focused areas start. If it was the mesh, the artifact would continue forwards of the focused area and not only be confined to areas beyond the focused points.

I hope that made sense...


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## Joe M (Mar 24, 2015)

Well colour me redfaced. Upon looking back at this thread, and a look at the photo enlarged (like I should have done to begin with), there is something in front of the oof branch that does indeed look like some sort of weird flare. Like Neuro mentioned, maybe something caught off of the fence? It does not appear in the other example although there is something similar but not as striking at the very top right hand corner. 
In any case, as I said before, at least it should be easily fixed in post if desired.


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## chromophore (Mar 24, 2015)

The correct term for this phenomenon is diffraction. In particular, an object that has been interposed between the lens and the subject in focus will cause light to diffract around it, creating Airy fringes. This is most familiar in the context of pinhole or slit photography, in which the narrow aperture makes the deflection most prominent, but it is important to remember that diffraction is a quantum phenomenon, and thus occurs at the boundary of any object that blocks incoming light rays.

Why, then, is the effect not visible in the area of the image that is in focus? Because here, the effect is too minor compared to the subject detail. Why is it visible in the out of focus areas? Because these areas tend to have smooth background blur. The effect is especially visible here because certain out of focus highlights will render as "doubled" due to light rays diffracting around either side of the obstacle (the fencing wires). If the source of this light is geometrically aligned with the obstacle, then the effect is also more pronounced.


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## TeT (Mar 24, 2015)

Thank you for that quick explanation...


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## Maximilian (Mar 24, 2015)

Thanks to all trying to help me get this thing understood. 

As the shape seemed to be geometrically round I was thinking about reflections or maybe also diffraction. 
But I am quite sure that either of both effects does not directly come from the fence. 
I am quite familiar with shoting through fences and mashes and as i said I am 90% sure that I managed to hit the center of one mesh (about 7 cm rectangular wide)
The fence was painted dark. And the bars (not wires) were straight horizontal and vertical. It was no wire mesh fence with small and diagonal meshes. The effects from these I know very well.



chromophore said:


> The correct term for this phenomenon is diffraction
> ...
> due to light rays diffracting around either side of the obstacle (the fencing wires)
> ...


Hi chromophore!

I was thinking about diffraction, too. And as fas as I could recall optical physics a straigt wire/bar would not lead into a round diffraction artifact. 

So this should come somewhere out of the optics. So more about reflection, maybe comming from a shiny screw in the fence. 

I was also thinking about *something comming from the IS*. At 400 mm and "just" 1/400 it could have been working if my hand was shaking a bit. 
But if you think you can sort this out, I'll leave it to beeing more alerted about reflections causing flare or diffraction. 

Thank you all once again.


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## chromophore (Mar 24, 2015)

We have to be very specific about the "artifact" that you are referring to. I am referring to the way the out of focus objects (what looks like twigs or branches) appear to have a "doubled" look, where there is a thin dark line running along the contour of the object, rather than a smooth transition. This effect is certain to be diffraction as I described earlier.


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## IMG_0001 (Mar 24, 2015)

It appears that everyone is not talking about the same artifacts. I'm talking about those that I highlighted (very delicately I should say) in this picture. I hope the OP is not offended that I retouched the image .

To me, this looks just like the reflection of where an element (or probably a filter) would be seated in its mount. I think it is possible that sunlight coming at a high angle could reflect from the filter ring, then on the front element and be picked up from there. Ok, now I'm repeating myself...


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## Maximilian (Mar 24, 2015)

IMG_0001 said:


> It appears that everyone is not talking about the same artifacts. I'm talking about those that I highlighted (very delicately I should say) in this picture. I hope the OP is not offended that I retouched the image .


Of course I am not offended. I was just too lazy to do that. :-[


> To me, this looks just like the reflection of where an element (or probably a filter) would be seated in its mount. I think it is possible that sunlight coming at a high angle could reflect from the filter ring, then on the front element and be picked up from there. Ok, now I'm repeating myself...


The *left *artefact - ending at the lynx' back seems to be some diffraction of a branch and seems to fall under the catetegory that Neuro was mentioning in his first post (100-400L MkI jittery bokeh) and it seems not to be a circular segment but a little bit different shaped.
The *right* artefact seems to be best explained with your argument of refection/diffraction of one optical element, filter or lens. 

Thank you again.


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