What makes good bokeh?

Started Apr 10, 2013 | Questions
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Juned D Prasetyo Forum Member • Posts: 83
What makes good bokeh?

I just curious. What exactly is make some lenses give a more pleasing creamy bokeh than others? With the same focal lenght and aperture. Some said the more aperture blade give more round aperture therefore, give more pleasing bokeh. But what if both lenses set on the widest aperture? Which ofcourse not involving any aperture blade shape. Is it because of lens material? Or are there other reasons?

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PHXAZCRAIG
PHXAZCRAIG Forum Pro • Posts: 12,639
Re: What makes good bokeh?

It will be interesting to see the responses, especially (for me) the technical ones.

I've observed (secondhand) that lenses with ED elements seem to have worse bokeh than ones without.

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slimandy Forum Pro • Posts: 16,518
Re: What makes good bokeh?

The shape of the blades and the number of blades are both important.

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(unknown member) Veteran Member • Posts: 4,624
Re: What makes good bokeh? Design, incl distance of blades from rear element...

Juned D Prasetyo wrote:

I just curious. What exactly is make some lenses give a more pleasing creamy bokeh than others? With the same focal lenght and aperture. Some said the more aperture blade give more round aperture therefore, give more pleasing bokeh. But what if both lenses set on the widest aperture? Which ofcourse not involving any aperture blade shape. Is it because of lens material? Or are there other reasons?

My understanding, albeit I am only an amateur and have NO design technical knowledge, this is from reading a bit on lenses..especially older ones...

- the immediate answer is the aperture design, including number of blades and shape. The reason for this is that as one stops down, the more blades and shape lend to a smoother shape i.e. roundness....allegedly. Some of the older Russian lenses have about 12 ot more blades and yes, they are known for smooth bokeh.

- something not often mentioned, seems to be the distance of the aperture blades from the rear element. There is a lens, cant remember which, that has a longer aperture to rear element distance, and the bokeh is butter smooth, I think the blades are not too many, nor specially shaped, so that is why someone mentioned anecdotally, that as possibly the reason for the lovely bokeh. Thinking about physics, that may make sense as the light rays have a longer travel after the blades, thus may become more dispersed, before hitting the rear element to become directed to the sensor. Thus, any shape abberations are smoothed out?

- sharpness vs bokeh. While the Zeiss lenses may be evidence against, some sharp lenses seem to have harsh bokeh. I have seen lovely bokeh from such as the 70-200 VRII in images, but some images have some 'hmmmm' bokeh. While some not so renowned lenses have lovely bokeh.

But then, look at Zeisss...they seem to have it all? But they are made 'amply. Also, the Nikkor 60mm 2.8 G and the Sigma 150mm 2.8 are both tack sharp and have lovely OOF rendering, from images I have seen.

I suspect the real reasons is a combination of the three i.e. overall design and element placement, aperture blades and location of aperture blades relative to the elements.

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jtra Contributing Member • Posts: 815
Re: What makes good bokeh?
1

Juned D Prasetyo wrote:

I just curious. What exactly is make some lenses give a more pleasing creamy bokeh than others? With the same focal lenght and aperture. Some said the more aperture blade give more round aperture therefore, give more pleasing bokeh. But what if both lenses set on the widest aperture? Which ofcourse not involving any aperture blade shape. Is it because of lens material? Or are there other reasons?

You are right, aperture blades are not that much important for bokeh. Wide open, they not involved, closed down the bokeh can be pleasing even when not fully round.

Light intensity in bokeh is not even. Such unevenness is caused by optical design. If more light is concentrated around edges than in center, the result will not be smooth.

I have written a whole article on that:

http://jtra.cz/stuff/essays/bokeh/

selected answer This post was selected as the answer by the original poster.
Bob GB Senior Member • Posts: 1,686
Re: What makes good bokeh?

Juned D Prasetyo wrote:

What exactly is make some lenses give a more pleasing creamy bokeh than others? With the same focal lenght and aperture. Some said the more aperture blade give more round aperture therefore, give more pleasing bokeh.

Bokeh describes the rendering of out of focus points. It is a function of many factors where the shape of the aperture is just one.

Complex lenses often display the effect of the various aberrations in the out of focus areas very clearly. The different colors from a point travel different ways through the lens before they come together in the focus point. But out of focus this could be quite disturbing. Also points toward the edges of the image do not use the whole cross section of some parts of the lens which make the shape of the out of focus spot ugly.

This has little to do with certain glass types. I would say ED glass will make the bokeh better rather than worse.

(unknown member) Veteran Member • Posts: 4,624
Re: What makes good bokeh? Zeiss article on lens design...
3

Also, reading this Zeiss article, note that the level of spherical correction can also contribuite to perception of bokeh.Bokeh from page 35 on.

http://www.zeiss.com/c12567a8003b8b6f/embedtitelintern/cln_35_bokeh_en/$file/cln35_bokeh_en.pdf

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Bob GB Senior Member • Posts: 1,686
Double posting

Double posting

flbrit Veteran Member • Posts: 3,666
Also read this by Zeiss
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Cytokine Contributing Member • Posts: 663
Amazing Bokeh control

This is one of my favourite Bokeh shots I found on flickriverhttp://www.flickr.com/photos/bimo_marwoto/3545419861/lightbox/

Taken it says with the 85mm 1.4D. one of many at this site under this lens, Here Nikon designer explains this lens http://imaging.nikon.com/history/nikkor/41/index.htm

What I think makes a good Bokeh lens (No order)

1) Isolation of subject.

2) Ability to blur a background very smoothly in a very short distance.

3) Many blades, at least 9 for round bokeh,.straight or rounded.

4) Smooth blur in front and behind the subject and in the transition zone.

5) High quality optical glass that transmits all colours strongly (New 1.4 G seems less transmissive of blue).

6) Clean defined circles with clarity that have little edging

7) No over complicated patterns that are nervous.

8) Designed specifically for purpose.

9) Have a mix of characteristics that can be applied to different requirements. (its a tool) too sharp not good for portraits, so open up, or stop down to increase sharpness but still retain blur.

I think the Nikon 85 1.4D version is so good because it is intentionally compromised in the corners at wide open stops, in exchange for rapid blurring, in effect it gives an extra stop open, of blur synthesised by its optical design, giving  an effective blur of a 1.2 lens, but the centre sharpness of a 1.4 aperture.

Compare this lens with the Canon 1.2L MK2 at photo zone, the depth of field in the playing cards, it also seems to have more contrast in the centre than the Zeiss, and 1.4G,  all but the Canon, and because the rapid blur is engineered, it gives better subject isolation than the Canon. Though the Canon is smoother in the transition zone by a tad.

The Canon costs even more than the Nikon 1.4G, circa $2,200. You can buy a used 85 1.4 D for circa $750 us dollars. (It is the combination of contrast and sharpness and optical design especially in the centre that makes this lens such a creative gem).

PS Nikon have many lenses with good bokeh and on a budget have a look at the old/new 80-200 2.8's  or the new 70-200's or the medium / long 2.8 primes, The DFC lenses. This 85 1.4 D lens is a specialist for portraits and photos that draw the eye to the centre of the image.

John

jopezu
jopezu Contributing Member • Posts: 512
Re: What makes good bokeh?

1) focal length - longer focal lengths compress backgrounds more.

2) subject-to-background distance - objects and scenery at longer distances behind the subject compress more.

3) lens design/ aperture blade design / sensor size - lots of technical (and sometimes subjective) things going on here, but some lens designs are just better at rendering bokeh than others.

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jubilatu Contributing Member • Posts: 510
Re: What makes good bokeh?

look at the MTF charts. if the dotted lines are [nearly] overlapping with the continuous ones, you have a bokeh-capable lens. the rest is tehnique.

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Shaun_Nyc
Shaun_Nyc Senior Member • Posts: 2,279
Re: Amazing Bokeh control
1

Cytokine wrote:

This is one of my favourite Bokeh shots I found on flickriverhttp://www.flickr.com/photos/bimo_marwoto/3545419861/lightbox/

Taken it says with the 85mm 1.4D. one of many at this site under this lens, Here Nikon designer explains this lens http://imaging.nikon.com/history/nikkor/41/index.htm

What I think makes a good Bokeh lens (No order)

1) Isolation of subject.

2) Ability to blur a background very smoothly in a very short distance.

3) Many blades, at least 9 for round bokeh,.straight or rounded.

4) Smooth blur in front and behind the subject and in the transition zone.

5) High quality optical glass that transmits all colours strongly (New 1.4 G seems less transmissive of blue).

6) Clean defined circles with clarity that have little edging

7) No over complicated patterns that are nervous.

8) Designed specifically for purpose.

9) Have a mix of characteristics that can be applied to different requirements. (its a tool) too sharp not good for portraits, so open up, or stop down to increase sharpness but still retain blur.

I think the Nikon 85 1.4D version is so good because it is intentionally compromised in the corners at wide open stops, in exchange for rapid blurring, in effect it gives an extra stop open, of blur synthesised by its optical design, giving  an effective blur of a 1.2 lens, but the centre sharpness of a 1.4 aperture.

Compare this lens with the Canon 1.2L MK2 at photo zone, the depth of field in the playing cards, it also seems to have more contrast in the centre than the Zeiss, and 1.4G,  all but the Canon, and because the rapid blur is engineered, it gives better subject isolation than the Canon. Though the Canon is smoother in the transition zone by a tad.

The Canon costs even more than the Nikon 1.4G, circa $2,200. You can buy a used 85 1.4 D for circa $750 us dollars. (It is the combination of contrast and sharpness and optical design especially in the centre that makes this lens such a creative gem).

PS Nikon have many lenses with good bokeh and on a budget have a look at the old/new 80-200 2.8's  or the new 70-200's or the medium / long 2.8 primes, The DFC lenses. This 85 1.4 D lens is a specialist for portraits and photos that draw the eye to the centre of the image.

John

Yes I agree about the D's bokeh

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