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Thread: Bokeh question

  1. #1
    benm's Avatar
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    Bokeh question

    New word for me but not a new concept. We used to call that out-of-focusness. I have read a lot how some lenses seem to have better "bokeh" than others and I am not sure what they really mean. If I took a group of lenses (multiple brands), primes and zooms, all set at the same focal length and aperture, and photographed a subject from the same distance would not the out-of-focus parts all look the same? If not, why not? These lenses would all be mounted to the same camera so the format size would not be a factor.

  2. #2
    Moderator Dave Humphries's Avatar
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    Re: Bokeh question

    Hi Ben,

    This mainly refers to how (very) out of focus 'speculars' are shown, by this I mean say; sunlight glints off chromework on a distance car fender/bumper.

    Some will be circular and soft, generally accepted I believe as 'good' bokeh, while others, usually on cheaper lenses with less aperture/iris leaves, maybe more ragged in shape.

    At least, that's what I think, it will be interesting if anyone can add to this definition for us.

    Cheers,
    Last edited by Dave Humphries; 4th March 2010 at 01:02 PM.

  3. #3
    PopsPhotos's Avatar
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    Re: Bokeh question

    If your bokeh space is "poor," you will be able to easily see the shapes and figures of the out of focus items. If your bokeh is "good," the out of focus items will be evenly blurred and will blend one into another more gradually.

    Ken Rockwell has a couple of good pages on this. (Remember, though, that this man admits to a sense of humor and started his site for his own amusement. )

    In this one, he gives a technical discussion of bokeh.
    http://www.kenrockwell.com/tech/bokeh.htm

    In this one he compares a number of lenses and shows examples of varying degrees of "goodness."
    http://www.kenrockwell.com/nikon/bokeh-comparison.htm

    "Good" and "poor" bokeh is definable. "good" or "poor" bokeh for an individual picture can become a matter of taste and artistic license.

    Pops

  4. #4
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    Re: Bokeh question

    I think good bokeh (for example in macro photography) should be an even blended soft background to help the subject to stand out. So what bokeh shouldn't do is distract your eye from the subject with sudden very bright spots or weird shapes.
    Though a more ragged shape fits the subject sometimes even better. And al the rest is a matter of artistic creativity or something I think.

    @ Pops
    unfortunately your links don't work. Would you mind to check them since the content seems rather interesting.

  5. #5
    rpcrowe's Avatar
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    Re: Bokeh question

    Depth of field is objective. It is the area between the near and far points of the image that provide acceptable sharpness. The acceptable sharpness of an image depends on the focal length, f/stop and distance focused on as well as the sensor or negative size. The sensor or negative size is important because it determines how much an image must be enlarged to provide a final product. A image from a smaller sensor or negative must be enlarged more to get your final result than an image from a larger sensor or negative and, therefore must be sharper.

    As an answer to your question, yes! An image shot with the same sensor/negative size, at the same f/stop and focused on the same distance will have the same depth of field.

    Now for BOKEH. Bokeh is a Japanese term for the subjective appearance of the areas which are out of focus. The differences in bokeh are caused by the shape of the lens aperture. A lens such as the Canon 50mm f/1.8 Mark-II has only five aperture blades and thus the shape of the aperture is not a clean round hole. It is somewhat ragged since five blades cannot make a clean circle. A lens such as my 90mm Tamron f/2.8 Macro has nine blades and those nine blades can form into a cleaner and more even circle as they are stopped down. The out of focus areas from my Tamron are more pleasing in looks than the out of focus areas from the 50mm f/1.8 lens. The bokeh formed by the 50mm is often described as "ragged" while the bokeh formed by the Tamron is often described as "smooth and creamy".

    Smooth bokeh is not distracting to me (see, I told you this was subjective) while ragged bokeh can tend to be distracting. We often use depth of field in order to accentuate the interest on our main subject but, when the OOF areas compete for that interest, the attempt fails somewhat. IMO, bokeh is particularly important in portraiture and in macro photography.

  6. #6
    PopsPhotos's Avatar
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    Re: Bokeh question

    @ Pops
    unfortunately your links don't work. Would you mind to check them since the content seems rather interesting.
    They are working for me, so I don't know how to change them for you. Try www.kenrockwell.com and scroll down to the search button. Type "bokeh" into the search bar and those two will come up (and some others.)

    Pops

  7. #7
    William W's Avatar
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    Re: Bokeh question

    Quote Originally Posted by rpcrowe View Post
    Now for BOKEH. Bokeh is a Japanese term for the subjective appearance of the areas which are out of focus.

    The differences in bokeh are caused by the shape of the lens aperture, a lens such as the Canon 50mm f/1.8 Mark-II has only five aperture blades and thus the shape of the aperture is not a clean round hole. It is somewhat ragged since five blades cannot make a clean circle.. A lens such as my 90mm Tamron f/2.8 Macro has nine blades and those nine blades can form into a cleaner and more even circle as they are stopped down. The out of focus areas from my Tamron are more pleasing in looks than the out of focus areas from the 50mm f/1.8 lens. The bokeh formed by the 50mm is often described as "ragged" while the bokeh formed by the Tamron is often described as "smooth and creamy".

    Smooth bokeh is not distracting to me (see, I told you this was subjective) while ragged bokeh can tend to be distracting. We often use depth of field in order to accentuate the interest on our main subject but, when the OOF areas compete for that interest, the attempt fails somewhat. IMO, bokeh is particularly important in portraiture and in macro photography.
    Gidday rp,

    Just on those two sentences . . . BOKEH (or the difference we see in BOKEH) may be contributed to by a number of things – one of which is the shape of the lens's aperture and / or the number of Iris Blades of that Lens.

    Some other contributing factors are, but not limited to:

    > the shape of the inner edge of the iris blades
    > the aperture at which the lens is used
    > the TYPE of lighting on the background
    > the ANGLE of lighting on the background
    > the nature of the material, comprising the background

    As an example – this is a “Portrait” was taken with the EF35F/2.

    Bokeh question

    This 35mm lens has only 5 Blades, but I suggest that the Bokeh in this image is reasonably smooth and creamy.

    But, I can use the same lens, in a Different Scene with a Different Lighting Scenario and make the BOKEH rougher and more ragged.

    ***

    I wrote this once, as a more flippant response to the question: What is BOKEH?

    “If one is to use Bokeh, then adjectives are usually necessary too: creamy, sublime, textured, soft; and the "bad" ones too: course; harsh; edgy . . .

    It seems that Bokeh rarely stands alone - it is usually qualified in some manner, or another.

    It can't just be "Bokeh" and just be there. I guess if it were strong enough to stand alone people would not respect it as much and it would it just be referred to as the out of focus bit . . . in the background . . .

    I understand the Out of Focus bit in the Foreground is "Hekob".

    Hekob is not revered as much as Bokeh.”


    ***

    So you can glean that I don’t elevate Bokeh all that much as a primary criterion for choosing any particular lens.

    But I do know how many blades my lenses each have – and for example, the number of blades was one reason I chose the EF50F/1.4 and not the EF50F/1.8MkII which you mentioned . . . one reason for my choice was because the 50F/1.4 has eight Blades and the F1.8MkII has only five Blades.

    I personally like eight blades over five Blades for two reasons.

    Firstly (and primarily) because eight is an even number and five is an odd number and that make a difference with iris reflections (Starbursts) - the second (minor) reason is the BOKEH the lens might be capable of more easily producing

    But if I can have three extra Blades then hey why not – because - if smooth BOKEH is important for the shot, then a few extra blades certainly can make smooth BOKEH easier to produce - and on that point, we agree.

    WW
    Last edited by William W; 6th March 2010 at 05:12 AM. Reason: just correcting my words and spelling

  8. #8

    Re: Bokeh question

    If you require good bokeh from any lens this can be achieved by holding a black card with a hole the shape of the bokeh you require in front of the lens. I discovered this as a young teenager, my only lens had a 4 blade aperture and produced square bokeh.
    Below is an example of what can be done with a piece of card.

    Bokeh question


    John
    Last edited by Dave Humphries; 7th March 2010 at 02:08 PM.

  9. #9
    The Blue Boy's Avatar
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    Re: Bokeh question

    As John says above, you can get any shape you wish using card. Below was meant to be christmas trees!

    Bokeh question

    However the term Bokeh is generally more associated with images such as this,

    Bokeh question

    Hope this helps.

  10. #10
    Moderator Dave Humphries's Avatar
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    Re: Bokeh question

    Mark (hi), John,

    What size should the shaped hole be? (say, in relation to the front element, as a percentage)

    Thanks,

  11. #11

    Re: Bokeh question

    Dave
    The relationship seems to be nothing to do with the size of the front element of the lens and more to do with the angle of view for the lens for a 100mm lens the angle of view is 23 degrees hole size about 10mm/ 50mm lens angle of view 47 degrees hole size 20mm. It looks like half the angle of view would be about right. Also this can only work if the lens is used near wide open. this can't be used with wide angle lenses as for a 24mm lens the angle of view is 84 degrees therefore the hole size would have to be 42mm
    I have tried it with my 28mm f2.8 macro
    john

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