Strange Problem with Bokeh Balls.

[alxtng]

Recently, I've been noticing that the bokeh balls in the background of my pictures appear to be cut off.
ex. (pay no attention to the subject of photo) I know that normally, it is the lens aperture shape. but my lens has 8 blades and appears to pretty circular when wide open. I've also heard that it could have something to do with something in the camera obstructing light? Does anyone know what is actually going on or know any solutions to this? It is just unappealing to me haha.

PS. Im using a T3 if that means anything

 

[Derrel]

There is no real solution to this issue.

Bokeh "balls" are NOT always perfectly rounded!!!! In fact, they may be elllipsoidal or otherwise weirdly out of round. In some situations, some of the light rays are being "clipped" by mechanical vignetting, either at the rear of the lens, or in the mirror box of the camera. I have a couple images on my pBase upload space, but cannot find them in the 7,000 images on-line there, showing the effects of mechanical vignetting from my Canon 70-200 f/2.8 L IS USM zoom and Canon 5D Classic camera; it cannot render truly ROUND bokeh balls on point light sources, but instead produces what are often called "cat's eye" bokeh, or "footballs".

Here...I just did a Google search. This might really help explain this!

optics - What is the cause of this non-uniform bokeh effect? - Photography Stack Exchange

 

[CameraClicker]

I'd like to see a couple of shots without the feet. Preferably shot on a tripod with the mirror locked up and lens wide open. In the sample shot I think the camera moved a little.

 

[Derrel]

Deeply-recessed and "baffled" interior of Canon 70-200/2.8 L IS USM on left:

[ DSC_0232CanonNikon.jpg photo - Derrel photos at pbase.com ]

And a photo made with the Canon on a full-frame camera, the original 5D: CLASSIC ellipsoidal or "Cat's eye" shaped bokeh, shot at f/2.8 on the 5D:

[ Canon 5D and 70-200 f/2.8 L IS USM Canon 70-200 at 2-8 at 200 on 5D.jpg photo - Derrel photos at pbase.com ]

Same subject matter shot on a CROP-sensored Nikon D2x, using the Nikkor 70-200mm f/2.8 AF-S VR-G (the original version) also at f/2.8, somewhat more rounded, but not perfectly rounded:

[ Nikon D2x at f2-8 at 200mm.JPG photo - Derrel photos at pbase.com ]

200mm f/2 VR-G stopped down one stop to f/2.8 and shot on D2x

[ _DSC0050_ccPROOF.jpg photo - Derrel photos at pbase.com ]

 

[CameraClicker]

Ain't that special. That's a lens (70-200 f/2.8 IS L) I don't use often. I can get a similar bokeh shape with a 5D Mk III. If I used that lens more, it might be a reason to upgrade to version II.

 

[CameraClicker]

Well, so much for the theory of the square mount aperture! These are from the
28-300


And, the 70-200 f/4


Both also have the pointy football shaped balls, but they have round mount apertures. It definitely looks like a Canon thing, but it isn't the rectangular aperture.

 

[Bender]

I had bokeh balls once.
Shot of penicillin cleared it up in no time.

 

[Derrel]

Well, so much for the theory of the square mount aperture!

Ummm, yeahhhh...

As you can see from the baffled rear and deeply recessed rear element on the 70-200 2.8 L- IS USM, that lens on the 5D produces elliptical bokeh balls wide-open ALL OVER THE ENTIRE frame, not just at the edges. The Canon is suffering from ellipsoidal or "Cat's eye" shaped highlights to a VERY serious degree...not one or two bokeh balls, but every one of them is elliptical...

 

[CameraClicker]

Well, so much for the theory of the square mount aperture!

Ummm, yeahhhh...

As you can see from the baffled rear and deeply recessed rear element on the 70-200 2.8 L- IS USM, that lens on the 5D produces elliptical bokeh balls wide-open ALL OVER THE ENTIRE frame, not just at the edges. The Canon is suffering from ellipsoidal or "Cat's eye" shaped highlights to a VERY serious degree...not one or two bokeh balls, but every one of them is elliptical...

I see that. I also see that the three shots I posted, with three different lenses, first with the 70-200 2.8 L IS USM, then with a 28-300 L, then with a 70-200 f/4 L, all shot with a 5D Mk III, look pretty much the same. If it had anything to do with the baffled rear and deeply recessed rear element, the other two photos should look different since the other two lenses don't have that rear element arrangement. I'm wondering if it has to do with the microlens on the sensor, since the Mk I and Mk III apparently get different bokeh from the same model of lens. As time permits I will try out different bodies and lenses to see if differences become apparent.