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Old May 1st, 2012, 01:32 PM
Jerome Marot Jerome Marot is offline
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Default Fight of the Bokeh titans.

(As Dave Barry would say, this title would make a good name for a rock band).

I shall say it up front: I have a weak spot for optics. I don't necessarily make better pictures for it, but I find it difficult to resist the call of the weird -optical engineer on acid- lens. I also have a weak point for bokeh and love the perspective given by a 100-135mm lens (on 35mm film). So the stars were aligned for the following test.

"Bokeh" a Japanese word (ぼけ) meaning "unsharp" is used to describe the appearance of the parts of a photographic image outside the plane of focus. I am sure you all know about it and how fuzzy elements can be nicely fuzzy or horribly fuzzy. Believe me, there is a whole theory behind it.

Camera lens manufacturers being what they are (that is: Japanese), there have been lenses designed especially for bokeh. For 35mm film or equivalent digital formats, two manufacturers shall be presented here: Nikon with their DC series lenses (that means "Defocus control") and Minolta (today: sold under the Sony brand) with the 135mm STF (that means "smooth trans focus", I swear I am not making this up).

Nikon has two "DC" lenses, a 105mm f/2.0 and a 135mm f/2.0. They are AF-D lenses, meaning screw-drive autofocus with a real aperture ring. They should work on most Nikon cameras. They are very well built, mostly metal, but have a real manual focus ring like in the old times. They are supposed to autofocus, but my experience has been that the DC feature fools the AF system wide open, even if you try to refocus. They are very sharp lenses, don't let yourself be fooled by the "defocus" in "DC". The bokeh part: they have a ring to adjust whether you want what is in front or to the rear part of the focal plane to look nicer. Optical engineers will understand that this command fiddles with the spherical aberration of the lens. You will find a review here or here.

Minolta issued a special bokeh lens in 1999, the 135mm STF. It is one weird piece of engineering: it won't AF (but has a manual focus ring better than the ones we had in the old times), has two diaphragms (only one is used at a time), one with a wealth of blades for the bokeh thing and confuses you with two set of apertures: T and F stops. It has the transmission of a f/4.5 lens with the depth of field of a f/2.8 lens (in plain English it is dark). It does not fiddle with aberrations as Nikon does, but uses an apodization element (which is a fancy word to describe a lens dark on the outside). There is a whole site devoted to it here. It is also a very sharp lens in its plane of focus, of course.

That was a very long introduction, but I suppose you understood where I was heading to: I had the occasion to compare the two lenses today. Here are the pictures:






and a different aperture:



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  #2  
Old May 1st, 2012, 01:59 PM
Mark Hampton Mark Hampton is offline
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Quote:
Originally Posted by Jerome Marot View Post
(As Dave Barry would say, this title would make a good name for a rock band).

I shall say it up front: I have a weak spot for optics. I don't necessarily make better pictures for it, but I find it difficult to resist the call of the weird -optical engineer on acid- lens. I also have a weak point for bokeh and love the perspective given by a 100-135mm lens (on 35mm film). So the stars were aligned for the following test.

"Bokeh" a Japanese word (ぼけ) meaning "unsharp" is used to describe the appearance of the parts of a photographic image outside the plane of focus. I am sure you all know about it and how fuzzy elements can be nicely fuzzy or horribly fuzzy. Believe me, there is a whole theory behind it.

Camera lens manufacturers being what they are (that is: Japanese), there have been lenses designed especially for bokeh. For 35mm film or equivalent digital formats, two manufacturers shall be presented here: Nikon with their DC series lenses (that means "Defocus control") and Minolta (today: sold under the Sony brand) with the 135mm STF (that means "smooth trans focus", I swear I am not making this up).

Nikon has two "DC" lenses, a 105mm f/2.0 and a 135mm f/2.0. They are AF-D lenses, meaning screw-drive autofocus with a real aperture ring. They should work on most Nikon cameras. They are very well built, mostly metal, but have a real manual focus ring like in the old times. They are supposed to autofocus, but my experience has been that the DC feature fools the AF system wide open, even if you try to refocus. They are very sharp lenses, don't let yourself be fooled by the "defocus" in "DC". The bokeh part: they have a ring to adjust whether you want what is in front or to the rear part of the focal plane to look nicer. Optical engineers will understand that this command fiddles with the spherical aberration of the lens. You will find a review here or here.

Minolta issued a special bokeh lens in 1999, the 135mm STF. It is one weird piece of engineering: it won't AF (but has a manual focus ring better than the ones we had in the old times), has two diaphragms (only one is used at a time), one with a wealth of blades for the bokeh thing and confuses you with two set of apertures: T and F stops. It has the transmission of a f/4.5 lens with the depth of field of a f/2.8 lens (in plain English it is dark). It does not fiddle with aberrations as Nikon does, but uses an apodization element (which is a fancy word to describe a lens dark on the outside). There is a whole site devoted to it here. It is also a very sharp lens in its plane of focus, of course.

That was a very long introduction, but I suppose you understood where I was heading to: I had the occasion to compare the two lenses today. Here are the pictures:






and a different aperture:



Minolta is on the bottom of the each set - smoother oof . i still have my dynax 7000i (or something) - nice work Jerome .. some more please !
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  #3  
Old May 1st, 2012, 07:16 PM
jake klein jake klein is offline
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More please! I also love OOF backgrounds and foregrounds.


So my question is, does the minolta "bokeh" control OOF areas independently(foreground/background) as the nikon does?

I love my nikkor 85mm f1.4 af-d and my tokina 100mm f2.8 macro's bokeh the most!


As Mark stated, yes more please!
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  #4  
Old May 1st, 2012, 09:20 PM
Doug Kerr Doug Kerr is offline
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Hi, Jerome,

Nice discussion and nice example images.

Thanks.

Best regards,

Doug
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  #5  
Old May 1st, 2012, 10:24 PM
Jerome Marot Jerome Marot is offline
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Quote:
Originally Posted by jake klein View Post
So my question is, does the minolta "bokeh" control OOF areas independently (foreground/background) as the nikon does?
No, it improves both at the same time.
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  #6  
Old May 2nd, 2012, 12:06 PM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Jerome Marot View Post
No, it improves both at the same time.
Hi Jerome,

Thanks for sharing the results. I didn't look at the EXIFs but I refer the bokeh in the second shot of each pair.

I think Jake was referring to a difference in foreground and background bokeh rendering, not a separate adjustment, just in case that point didn't come across. I do often see a marked difference in how the foreground bokeh is rendered, compared to the background bokeh. That may be an important lens characteristic to know for certain types of shooting.

Cheers,
Bart
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  #7  
Old May 2nd, 2012, 02:56 PM
Asher Kelman Asher Kelman is online now
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Jerome,

I too like "bokeh" or rather "soft focus" lenses. To me, it's yet another smart way to reduce the importance of distractions and even convert them into a beautiful canvas on which to isolate what's of most interest. After all, that's part of the lore of artistic photography once one has exited from attempts at honest documentation, inventory and the like.

I too prefer the second of each pair. The first has a harsher background blur.


So here together are both your second photographs to compare them at the different aperture:




[/url]


I'll look at these and then discuss below.

Asher
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  #8  
Old May 2nd, 2012, 03:17 PM
Mark Hampton Mark Hampton is offline
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Quote:
Originally Posted by Asher Kelman View Post
Jerome,

I too like "bokeh" or rather "soft focus" lenses. To me, it's yet another smart way to reduce the importance of distractions and even convert them into a beautiful canvas on which to isolate what's of most interest. After all, that's part of the lore of artistic photography once one has exited from attempts at honest documentation, inventory and the like.

I too prefer the second of each pair. The first has a harsher background blur.


So here together are both your second photographs to compare them at the different aperture:




[/url]


Asher
jerome - what did you make these on? camera film.digital?

cheers
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  #9  
Old May 2nd, 2012, 03:26 PM
Asher Kelman Asher Kelman is online now
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Default The Second lens at two different apertures.




[/url]


Particular dandelions seem to be, (by your intent), more important. Judging by these, the second of the two seems sharpest at the flowers. That's the shot I get the best experience of "dandelion identity" and enjoy the most. I'd imagine that my choice could very well be independent of the subject, but that's a guess.

Thanks for sharing. Now do you consider regular lenses like the f1.2 50mm and 85mm Canon/Nikon lenses in your stable lenses with "bokeh" in the class of these two lenses you've shared so far? What do they miss?

Asher
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  #10  
Old May 2nd, 2012, 10:35 PM
Jerome Marot Jerome Marot is offline
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Quote:
Originally Posted by Bart_van_der_Wolf View Post
I think Jake was referring to a difference in foreground and background bokeh rendering, not a separate adjustment, just in case that point didn't come across. I do often see a marked difference in how the foreground bokeh is rendered, compared to the background bokeh.

This is the case with all lenses which rely on residual spherical aberrations to improve bokeh: they will have good bokeh in the background and poor bokeh in the foreground or vice-versa. This is the reason why the Nikon lens has an adjustment ring going in two directions.

The Minolta-Sony lens uses a different principle and improves the two sides at the same time.
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  #11  
Old May 2nd, 2012, 10:38 PM
Jerome Marot Jerome Marot is offline
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Originally Posted by Mark Hampton View Post
jerome - what did you make these on? camera film.digital?
Digital cameras. A Nikon D700 and Sony A900.
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  #12  
Old May 2nd, 2012, 11:03 PM
Jerome Marot Jerome Marot is offline
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Originally Posted by Asher Kelman View Post
I too like "bokeh" or rather "soft focus" lenses.
These are not soft focus lenses. They are supposed to be sharp in the plane of focus. Soft focus lenses add some "glow" to the subject at the plane of focus.

Quote:
Originally Posted by Asher Kelman View Post
Particular dandelions seem to be, (by your intent), more important. Judging by these, the second of the two seems sharpest at the flowers. That's the shot I get the best experience of "dandelion identity" and enjoy the most. I'd imagine that my choice could very well be independent of the subject, but that's a guess.
These are just test pictures taken to show the rendition of the background, but you noted an effect of the Nikon lens: adjusting the bokeh degrades the correction of aberrations and, therefore, also renders the subject less sharp in the plane of focus.

Quote:
Originally Posted by Asher Kelman View Post
Thanks for sharing. Now do you consider regular lenses like the f1.2 50mm and 85mm Canon/Nikon lenses in your stable lenses with "bokeh" in the class of these two lenses you've shared so far? What do they miss?
Large aperture lenses, particularly the ones designed for portrait as the 85mm usually are, are usually designed with bokeh in mind, so your particular examples may not "miss" anything.

To determine the quality of bokeh, one may try to see how a defocused point source looks. Ideally, it should have a round shape with edges going darker gradually (what the STF produces). On lenses with bad bokeh, the edges are brighter than the center. The following article explains more: http://www.luminous-landscape.com/essays/bokeh.shtml.

Here, the gravel in the background is an object that will easily produce distracting backgrounds, which is why I chose it. OTOH, the rendering of plant parts is easier to blur and you will notice less difference between the two lenses on these zones.
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Old May 3rd, 2012, 12:23 AM
Asher Kelman Asher Kelman is online now
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Quote:
Originally Posted by Jerome Marot View Post
These are not soft focus lenses. They are supposed to be sharp in the plane of focus. Soft focus lenses add some "glow" to the subject at the plane of focus.
That, Jerome, is an interesting position. The recognition of "Bokeh" as a separate esthetic seems to be quite recent. In the beginning of the 20th century, efforts were made to counteract the precise way the entire image, especially in portraits, was being made. Narrow depth of field helped soften the background.

You are quite right that additional steps were taken to soften the part of the image in the maximum focus. Specular light from the periphery was focused to the same plane, making highlights glow. Extra diaphragms with various patterns of apertures in the periphery, could also do approach this effect.

I have several lenses that use just optical means by virtue of the lens design alone: the PS945 Cooke Portrait lens and the Pinkham and Smith Visual Quality. In each case, at f4.5 the lenses provide wonderful OOF bokeh and a glow in the in focused subject.

Asher
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  #14  
Old May 3rd, 2012, 01:19 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Jerome Marot View Post
These are notTo determine the quality of bokeh, one may try to see how a defocused point source looks. Ideally, it should have a round shape with edges going darker gradually (what the STF produces). On lenses with bad bokeh, the edges are brighter than the center. The following article explains more: http://www.luminous-landscape.com/essays/bokeh.shtml.
Hi Jerome,

indeed, that's a good article about bokeh. Here is another, with a link at the bottom to more Nikon examples :
http://toothwalker.org/optics/bokeh.html.

Cheers,
Bart
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Old May 3rd, 2012, 03:48 AM
Jerome Marot Jerome Marot is offline
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Originally Posted by Asher Kelman View Post
That, Jerome, is an interesting position. The recognition of "Bokeh" as a separate esthetic seems to be quite recent. In the beginning of the 20th century, efforts were made to counteract the precise way the entire image, especially in portraits, was being made. Narrow depth of field helped soften the background.

You are quite right that additional steps were taken to soften the part of the image in the maximum focus. Specular light from the periphery was focused to the same plane, making highlights glow. Extra diaphragms with various patterns of apertures in the periphery, could also do approach this effect.

I have several lenses that use just optical means by virtue of the lens design alone: the PS945 Cooke Portrait lens and the Pinkham and Smith Visual Quality. In each case, at f4.5 the lenses provide wonderful OOF bokeh and a glow in the in focused subject.

Asher
Improving the optics in that manner is indeed old, but you should realize that there have been more recent developments. For 35mm, Canon and Minolta manufactured soft focus lenses where a lens is moved to add spherical aberration (but for the blur effect, not necessarily for bokeh). There have been filters from Zeiss and Minolta with tiny flat lenses on their surface to produce a similar effect. The filters are quite clever in that the effect is stronger in the red part of the spectrum, so as to give maximum smoothing for skin tones.

Of course, these effects can be done with software today.
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Old May 3rd, 2012, 08:39 AM
Asher Kelman Asher Kelman is online now
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Quote:
Originally Posted by Jerome Marot View Post
Improving the optics in that manner is indeed old, but you should realize that there have been more recent developments. For 35mm, Canon and Minolta manufactured soft focus lenses where a lens is moved to add spherical aberration (but for the blur effect, not necessarily for bokeh). There have been filters from Zeiss and Minolta with tiny flat lenses on their surface to produce a similar effect. The filters are quite clever in that the effect is stronger in the red part of the spectrum, so as to give maximum smoothing for skin tones.
I recently came across a cinematography filter by Zeiss for the faces of female anchors and stars to provide a more flattering appearance. I guess they have that stronger red effect you mention.

Quote:
Originally Posted by Jerome Marot View Post
Of course, these effects can be done with software today.
But not on the fly for live broadcast!! Or maybe things have moved even faster than I could imagine!

Asher
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  #17  
Old May 3rd, 2012, 09:44 AM
Jerome Marot Jerome Marot is offline
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But not on the fly for live broadcast!! Or maybe things have moved even faster than I could imagine!
Things have moved faster than you imagined. Even on amateur camcorders (admittedly, not the cheapest ones), you have a function to apply a blur filter just to skin tones and a function to make the sky really blue. I am pretty sure my old Canon XH-A1 had these filters in 2007.
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