Post your Christmas (bokeh) lights pics!

[DScience]

Oh, and here's my submission for the thread.

I would have to say that this isn't the best example of bokeh, but this shot is freaking awesome! There is something very mysterious about it, and I really like the lighting.

 

[inTempus]

I have wondered about this! But since I have seen it with all my lenses, I thought it was a matter of distortion caused by the emitted light being off center from the focus point. My thinking was that only the light being focused on was coming into the lens at a straight line, hence the perfect circle from the wide open aperture. Then I thought that the 'cat eye' ones were caused because the light is being bent somewhat or refracted, and thus you get an imperfect circle.

This isn't an easy subject to get a technical explanation of... at least one that's easy to understand.

Bokeh

It is also well known that out-of-focus highlights (OOFHs) assume the shape of the lens aperture. At reduced apertures the shape of the blur disk is the same as that of the diaphragm opening. For instance, a six-sided diaphragm leads to hexagonal blur patches. 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 OOFHs scattered across the frame, the cat's eye effect yields the impression of a rotational background motion (Fig. 2).

...

The consequences of optical vignetting for a subject that is in focus (cf. Fig. 1) is merely a reduced brightness towards the image corners. However, optical vignetting can also have a pronounced effect on out-of-focus parts of the image. Because the shape of an out-of-focus highlight (OOFH) mimics the shape of the clear aperture, the bottom left situation of Fig. 2 leads to the so-called cat's eye effect [1]. Figure 3 evidences the resemblance between the appearance of OOFHs and the aperture shape. With an increasing distance from the optical axis the shape of the OOFH progressively narrows and starts to resemble a cat's eye. The larger the distance from the image center, the narrower the cat's eye becomes.

It would appear that the "cats eye" effect is caused by the size of the aperture and the angle at which the light enters the lens. In my example above I used a f/1.2 setting to easily create the effect. As we suspected, it's not only a result of the aperture size but also where the blurred subject appears in relation to the center of the lens. In the center of the lens, the subject will appear round. Out towards the edges it will begin to exhibit the cats eye effect. This also holds true with my example in that the Christmas tree is left of center in my image.

So, it's caused by the aperture and the angle at which the light enters the lens which makes sense if you think about it.

 

[inTempus]

Oh, and here's my submission for the thread.

I would have to say that this isn't the best example of bokeh, but this shot is freaking awesome! There is something very mysterious about it, and I really like the lighting.

Thanks. I actually blurred and darkened the tree in the background to achieve the look I wanted. You're right, it's not a good example of bokeh but I shot the image before I read this thread today.

 

[Derrel]

You did a bit of reseatch, but I did a bit more....


"Much of the "swirly bokeh" effect of the Helios 40 is due to the optical vignetting of the lens. That is, the out of focus highlights away from the center are partially obscured by the lens tube itself, due to its insufficient diameter in view of the large aperture of the lens. As a consequence, the out of focus highlights turn into a cat's eye shape, instead of their normal circular shape. For more on optical vignetting, see this excellent page on Paul van Walree's website: Vignetting

"... it is more efficient to use a black cardboard tube mounted on the rear of the lens to artificially increase optical vignetting. Unfortunately, this usually is not possible with DSLRs, because there isn't sufficient space available at the back of the lens, due to the mirror clearance. The only exceptions are macro lenses designed to be used on bellows or medium format lenses used with adapters. "

Okay, so, if you WANT TO CREATE the cat's eye style of bokeh, an efficient way to do that is to use a black cardboard tube mounted to the rear of the lens--that is EXACTLY WHAT CANON HAS DONE with the design of the 70-200 f/2.8 L-IS lens; the rear element of the lens is recessed almost exactly 5/8 inch from the back edge of the lens mount, and the aperture is a SQUARE, with radiused corners. For the bokeh freaks, many of whom use rangefinder cameras and hang out at The Manual Focus Forum, they actually recognize what causes this issue. SOme people actually like the football-shaped bokeh--the Manual FOcus Forum has a few people, and I eben found the above thread that describes how to CAUSE the effect by adding a tube to the rear of the lens!

Here is the defacto black tube Canon slapped onto the back of the 70-200/2.8 L-IS lens--only it's not cardboard, it's solid metal! And it causes the cat's eye effect when the lens is shot at f/2.8. The Canon's rear element is recessed 5/8 inch, down inside that square-ish hole...thus leading to clipping off of the edges of the light leaving the lens at what is known as "the exit pupil". The Nikon lens shown has an exposed rear element that is right at the top--making it unsuitable for use with a modern 1.4x or 2.0x autofocus teleconverter, which protrudes INTO the lens barrel.

 

[inTempus]

Okay, so, if you WANT TO CREATE the cat's eye style of bokeh, an efficient way to do that is to use a black cardboard tube mounted to the rear of the lens--that is EXACTLY WHAT CANON HAS DONE with the design of the 70-200 f/2.8 L-IS lens; the rear element of the lens is recessed almost exactly 5/8 inch from the back edge of the lens mount, and the aperture is a SQUARE, with radiused corners. For the bokeh freaks, many of whom use rangefinder cameras and hang out at The Manual Focus Forum, they actually recognize what causes this issue...

The only problem I can see with this is that the exact same effect can clearly be seen on lenses that have no such tube on the rear. It's just as bad with lenses that lack this, as evidenced with my 50mm example above. As a matter of fact, just about every lens available will experience this effect and it has nothing to do with Canon vs. Nikon from what I can tell, as I've clearly shown examples from both manufacturers.

So, as noted, it appears to be more of a factor based upon aperture size and the angle of light coming into the lens more than anything.

 

[inTempus]

Here is the defacto black tube Canon slapped onto the back of the 70-200/2.8 L-IS lens--only it's not cardboard, it's solid metal! And it causes the cat's eye effect when the lens is shot at f/2.8.

Then how do you explain it happening with other lenses that don't have this design, both Canon and Nikon? I can easily cause the exact same effect with a 50mm lens, and to the same degree, and it lacks this "tube" on the rear. I think that pokes a pretty big hole in that theory.

 

[Dao]

Here is the defacto black tube Canon slapped onto the back of the 70-200/2.8 L-IS lens--only it's not cardboard, it's solid metal! And it causes the cat's eye effect when the lens is shot at f/2.8.

Then how do you explain it happening with other lenses that don't have this design, both Canon and Nikon?

That was being discuss in the past.

http://www.thephotoforum.com/forum/...ws/168536-strange-bokeh-canon-85-f-1-8-a.html

 

[inTempus]

Here is the defacto black tube Canon slapped onto the back of the 70-200/2.8 L-IS lens--only it's not cardboard, it's solid metal! And it causes the cat's eye effect when the lens is shot at f/2.8.

Then how do you explain it happening with other lenses that don't have this design, both Canon and Nikon?

That was being discuss in the past.

http://www.thephotoforum.com/forum/...ws/168536-strange-bokeh-canon-85-f-1-8-a.html

It looks like folks came to the same conclusion that I have. It's related to the aperture size and angle of the light coming into the lens.

As the OP in that thread noticed, he could cause it both with the 50mm and 70-200 pretty easily and they don't share the same design on the rear element.

 

[Derrel]

As a matter of fact, just about every lens available will experience this effect and it has nothing to do with Canon vs. Nikon from what I can tell, as I've clearly shown examples from both manufacturers.


Sorry but NO your assertion is simply wrong, and the cat's eye bokeh effect will NOT occur with "just about every lens". The photo below was shot in front of the same Christmas tree and the same minilights. It was shot by a Nikon lens that displays almost perfect bokeh; this lens does not create cat's eye bokeh. Why are you trying to make this about Canon and Nikon--it is about lens design, Tim, lens design. And lens design choices the designers made. I am not generalizing this to brands--you are. I am talking about *specific* lenses and a *specific* issue relating to bokeh, which is actually an area I am pretty well experienced in...

 

[inTempus]

Sorry but NO your assertion is simply wrong, and the cat's eye bokeh effect will NOT occur with "just about every lens". The photo below was shot in front of the same Christmas tree and the same minilights. It was shot by a Nikon lens that displays almost perfect bokeh; this lens does not create cat's eye bokeh. Why are you trying to make this about Canon and Nikon--it is about lens design, Tim, lens design. And lens design choices the designers made. I am not generalizing this to brands--you are. I am talking about *specific* lenses and a *specific* issue relating to bokeh, which is actually an area I am pretty well experienced in...

First, I didn't say "every", I said most. I have evidence to prove it too. It's called Flickr.

Here are some examples:
A D300:
I will shine on on Flickr - Photo Sharing!

Another D300:
Wage & The Holga Filter on Flickr - Photo Sharing!

A D90:
Merry Christmas on Flickr - Photo Sharing!

And a D200:
a new season on Flickr - Photo Sharing!

Your contention it's strictly the result of the 70-200's rear element design is inaccurate, and I've proven that with actual pictures (as have others).

The effect is certainly the result of lens design, I don't argue that at all. What I'm arguing is your assertion it's the result of a tube appearing on the back of "many L lenses" that is at fault. That's simply inaccurate as lenses that do not share this design exhibit the effect in spades.

So, what we can agree upon is that not all lenses exhibit the effect. It occurs in more lenses than Canon L glass (contrary to your assertion it's a Canon L lens design issue) and it's not something unique to any particular brand.

 

[inTempus]

Further proof it has to do with aperture size. I suspect it also has to do with the distance of the camera from the subject, the subject from the background, and other elements that effect bokeh in general.

50mm f/1.2:

50mm f/2.8:

The only difference? Aperture size. I didn't put any cardboard tubes on the back of my 50mm lens.

 

[ottor]

I'm extremely new to photography, and personally have absolutely no experience with 35mm, but a friend of mine thought that Nikon used to have a series of "DC" or "Defocus Control" 35mm lenses that actualy allowed you to change the amount of spherical aberration for better control ? It apparently allowed you to place the 'good' bokah in either the foreground or background... Anyone who has 35mm experience have any comments or experience with these types of lenses?

tks,

r

 

[Aye-non Oh-non Imus]

^^ yes ottor... THIS ONE

 

[inTempus]

For more on optical vignetting, see this excellent page on Paul van Walree's website: Vignetting

From your own source (which ironically is my original source):

Optical vignetting tends to be stronger in wideangle lenses and large aperture lenses, but the effect can be noticed with most photographic lenses. Zoom lenses are often saddled with a fair amount of optical vignetting.

Then your comment to me:

Sorry but NO your assertion is simply wrong, and the cat's eye bokeh effect will NOT occur with "just about every lens".

So it appears your source agrees with my statement, the same statement you said I was wrong for making.

I suspect under the right circumstances even the Nikkor lens you're showing as an example of lenses that don't demonstrate the effect will actually demonstrate it to some degree.

Just a guess though.

 

[Rekd]

Is so!

Is not!

Is so!

Is not!

Is so!

Is not!

Bokeh bokeh BOOM! :lmao: