The ultimate Bokeh thread; pics please

[Abbazz]

more often, coma is referred to as any aberration producing any kind of asymmetrical distortion of points in the image. Since lenses are round, typically these distortions appear in radial symmetry to the image center, which creates the impression of circles. Tails, comet stars and shapes that look like flying birds are only one variant. Elipses are another one.

Roland, let me call old Kingslake (Lenses in Photography, Garden City Books, New York, 1951) to the rescue:

Coma has the effect of producing a rather unpleasant one-sided radial blurring of images lying in the outer parts of the field. (emphasis is mine)

Here's the paragraph about vignetting, from the same book:

Cheers!

Abbazz

 

[ferider]

Roland, let me call old Kingslake (Lenses in Photography, Garden City Books, New York, 1951) to the rescue:

Coma has the effect of producing a rather unpleasant one-sided radial blurring of images lying in the outer parts of the field. (emphasis is mine)

I think we agree, Abbazz. Allow me to illustrate using your picture. Looks
like one-sided radial blurring to me.

Roland.

 

[Abbazz]

I think we agree, Abbazz. Allow me to illustrate using your picture. Looks
like one-sided radial blurring to me.

Roland, the problem I have with your concept is that coma also affects highlights in sharp focus. I have never seen those comet shaped highlights that should be present in the areas of sharp focus on shots taken with the Noctilux or the Classic Heliar 50/2. I have never heard that the Heliar is affected by coma either.

Cheers!

Abbazz

 

[ferider]

Roland, the problem I have with your concept is that coma also affects highlights in sharp focus.

I'm flattered but it's not my concept, Abbazz. I guess it's a softening of terms over time. It used to be called sagittal oblique spherical aberration, but now many people - me included - just call it coma.

See for instance http://photo.net/bboard/q-and-a-fetch-msg?msg_id=00MSoT Scroll to the very end which shows a butterfly example - (I saw my first example, called coma there, too, in the Leica Lens Compendium I think).

The strict definition of the term as you use it is found for telescopes, I believe, not really for photographic lenses. But I'm an electrical engineer not a physicist

Roland.

 

[ampguy]

Osterloh Leica M book reference

Osterloh Leica M book reference

Roland,

Would you consider the p. 103 explanation of coma accurate - "Coma causes individual points of light to be reproduced as butterfly-like images. The further away the point is from the center of the image, the more pronounced is the effect?

The image shows a dot at image radius 0mm moving to a sideways teardrop to a sideways chocolate kiss eventually to a butterfly or arrow shape at 18mm.

I also don't see the swirly bokeh in the small sample of Noctilux photos I've taken, but I have seen non-circular football shaped lights in the OOF areas in mine, and other Noct photos, which I kind of like, along with the watercolor painting effect, that I can't quite clarify, as it's not defined in any of the books I have.

I'm flattered but it's not my concept, Abbazz. I guess it's a softening of terms over time. It used to be called sagittal oblique spherical aberration, but now many people - me included - just call it coma.

See for instance http://photo.net/bboard/q-and-a-fetch-msg?msg_id=00MSoT Scroll to the very end which shows a butterfly example - (I saw my first example, called coma there, too, in the Leica Lens Compendium I think).

The strict definition of the term as you use it is found for telescopes, I believe, not really for photographic lenses. But I'm an electrical engineer not a physicist

Roland.

 

[ferider]

Yes, Ted, except butterflies are the extremes. Can be elipses/footballs, too,
in a better corrected lens. Just radially symmetric, and the further
away from the center the worse.

More pics please ....

Roland.

 

[xayraa33]

the lens that was the King ( or Queen?) of swirlies was that Paxette lens that Brian cobbled up in LTM and owned by our very own Raid.
this thing had swirlies to spare.

 

[amin_sabet]

Well I don't know much about lenses, but coma and specifically sagittal oblique spherical aberration are intrinsice lens properties, right? If Abbazz is correct that attaching a cardboard tube to mechanically vignette the rear element causes the swirly bokeh, then it can't be due to coma, can it?

 

[ferider]

Well I don't know much about lenses, but coma and specifically sagittal oblique spherical aberration are intrinsice lens properties, right? If Abbazz is correct that attaching a cardboard tube to mechanically vignette the rear element causes the swirly bokeh, then it can't be due to coma, can it?

Try it and report Any more pics to share ?

 

[Andrew L]

Please excuse the sentimental nature of the subject. As a model, she is easily bribed.

This was a test shot taken with a 1920s 6" Cooke on a 6x9 Thornton Pickard SLR. I have seen a few exapmples of swirly bokeh from old lenses. Personally speaking, I find that too distracting. I prefer what I can get with old Cookes.

 

[foto_fool]

Roland: Love the night shot of the cathedrals at Lyon. Funny how a photo can make me hungry and thirsty .

35mm UC Hexanon on the R-D1 at f2.0.

 

[ferider]

Roland: Love the night shot of the cathedrals at Lyon. Funny how a photo can make me hungry and thirsty .

I proposed it for the planned RFF Europe get together. But the crew preferred Berlin. They don't know what they're missing, John ! Nice photos.

 

[amin_sabet]

John, do you get swirly bokeh with the 50/1.2 FD?

 

[Abbazz]

Well I don't know much about lenses, but coma and specifically sagittal oblique spherical aberration are intrinsice lens properties, right? If Abbazz is correct that attaching a cardboard tube to mechanically vignette the rear element causes the swirly bokeh, then it can't be due to coma, can it?

Amin, don't listen to the naysayers and have a look at this page: http://www.vanwalree.com/optics/bokeh.html

Here's a quote:

Generally, the better an aperture approximates a round opening, the more pleasing the blur. However, when a lens is used at a large aperture, obliquely incident light is confronted with a narrower aperture than normally incident light. Consequently, the blur disk narrows from the image center towards the corner. This is known as the cat's eye effect, a result of optical vignetting. When there are many OOFH's scattered across the frame, the cat's eye effect yields the impression of a rotational background motion (Fig. 2).

Figure 2. Optical vignetting creates a sense of rotational motion of the background around the street sign. Photograph by Edo Engel.​

Just google the words "cat's eye vignetting" for more picture samples.

Cheers!

Abbazz

 

[Abbazz]

How about some more pics, Abbazz ?

Sure.

To get back on the topic of rangefinder's lens bokeh and to put an end to this arid technical discussion, here's the swirly bokeh of my Elmar 135/4 when used with a black cardboard tube and a (non circular) stop stuck behind the lens to obstruct part of the lens rear pupil:

And no, my Elmar doesn't exhibit coma. Here is a picture taken with the same lens without the vignetting contraption:

Cheers!

Abbazz

 

[ferider]

From Joe's shootout last Sat. 75/1.4 wide open:

Good bokeh Best,

Roland.

 

[ampguy]

I like the one with the tube

I like the one with the tube

If you could affix that cardboard in there permanently, you might be on to something!

Sure.

To get back on the topic of rangefinder's lens bokeh and to put an end to this arid technical discussion, here's the swirly bokeh of my Elmar 135/4 when used with a black cardboard tube and a (non circular) stop stuck behind the lens to obstruct part of the lens rear pupil:

And no, my Elmar doesn't exhibit coma. Here is a picture taken with the same lens without the vignetting contraption:

Cheers!

Abbazz

 

[Abbazz]

If you could affix that cardboard in there permanently, you might be on to something!

This "swirly bokeh device" is not very usable on small format, because it has to be behind the lens to provide the best results. The tube needs to be around 50mm long but, on 35mm cameras, there is not much space behind the lens, especially with an SLR. That's why I used my old Elmar lens, because it's a 135mm and because the lens unit can be separated from the focusing helicoid, thus enabling the lens to be mounted on a bellows with sufficient space to put the vignetting tube behind the lens.

On a large format camera, it is much easier to mount a 50mm cardboard cone behind the lens to get this effect.

Here are three more pictures taken this morning with the "swirly Elmar":

And here is the bellows with an universal iris lensmount on my K10d ready to receive the Elmar lens unit:

Cheers!

Abbazz

 

[ampguy]

That setup looks dangerous!

 

[Abbazz]

That setup looks dangerous!

It doesn't bite though

Cheers!

Abbazz