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08-08-2011, 01:35 PM   #1
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Bokeh effect

I have been taking pictures with my new K-r(18-55 kit lens) and noticed that when the aperture is wide open at 3.5 I do not get background blur effect but at times even when its f/5.6 or 6.3 I get nice blurry background.

Isn't the bokeh effect supposed to be more at large aperture ? Could anyone explain me what am I doing wrong ? I am new to DSLR photography and trying to get the best out of kit lens

08-08-2011, 01:41 PM   #2
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The background needs to be suitably distant to blur. Move your subject further from the back ground and the background will dissolve.

check out some of the photos in the kit lens club thread - some real inspiration there.

oh, & Have fun!!

heh, read Fries post below and realized that mine + his gives the full explaination.. this LINK is useful for understanding DoF (Depth of Field)

Last edited by mattt; 08-08-2011 at 01:49 PM. Reason: Added link
08-08-2011, 01:47 PM   #3
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I am not very good in explaining this sort of things but it has to do with the distance to your subject. Get closer and you will find it easier isolating it from its surroundings and produce bokeh... You will have less in focus and you have to pay extra attention to that!
08-08-2011, 01:57 PM   #4
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oh, I get it..so I have to move closer to the subject but at the same time the subject has be at a suitable distance from the background to produce the effect.

Thanks Mattt n Fries

08-08-2011, 02:55 PM   #5
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QuoteOriginally posted by lovejoy Quote
I have been taking pictures with my new K-r(18-55 kit lens) and noticed that when the aperture is wide open at 3.5 I do not get background blur effect but at times even when its f/5.6 or 6.3 I get nice blurry background.

Isn't the bokeh effect supposed to be more at large aperture ? Could anyone explain me what am I doing wrong ? I am new to DSLR photography and trying to get the best out of kit lens
In addition to the other good suggestions, you might check out this Zeiss article, though it gets a bit technical at times; and this thread where some good stuff was discussed. I quoted from the Zeiss article in that thread:

"A composition parameter which can help us to achieve this objective is the adjustment of the blurring in front of and behind the main subject by a suitable combination of aperture, focal length and taking distance. . . . blurring always depends on a large number of parameters. . . . All the parameters listed here influence the phenomena outside the focal plane:

Picture format
Focal length
f-number
The camera-to-subject distance
Distance to the background or the foreground
Shapes and patterns of the subject
Aperture iris shape
Aberrations of the lens
Speed of the lens
Foreground/background brightness
Colour


One thing to keep in mind is that according to the Zeiss article (page 26), some lenses may be incapable of buttery-smooth bokeh because the aperture values "reach a kind of saturation beyond a background distance of about 10 m. Thus, the blurring does not become any greater at larger distances":

"The chart describes a typical photographic situation e.g. in portrait photography: the object field is 70cm wide and photographed in 35 mm format with an 85mm lens. The focus distance to the main subject set on the lens is therefore 1.8 metres.
The distance of the background from the main subject is indicated on the horizontal axis; the vertical axis shows the size of the circle of confusion with reference to the image diagonal. Therefore in this chart the region of the depth of field with which we have been concerned in the first part is up at the top on the left, just outside the scale; at this point the circles of confusion are diagonal/1500 or less; we are there still close to the focus; as we move to the right we move away up to a distance of 100 metres in the background.
Each curve in the chart represents one of the aperture values specified in the legend and all curves have the same character. Initially they fall uniformly (in this process the circles of confusion gradually become larger) and then reach a kind of saturation beyond a background distance of about 10 m. Thus, the blurring does not become any greater at larger distances. This limit depends, of course, on the aperture and when we compare the figures with our experience or just try it with our camera , we learn that we need circles of confusion larger than 1/100 of the diagonal in order to separate the main subject from the background."
08-09-2011, 09:45 AM   #6
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Are you shooting in auto focus or manual focus? I've struggled to get that effect in auto focus. A little easier in manual focus. I'm pretty sure everyone is right about the effect in regards to distance.

I've found it pretty hard to get a Bokeh effect with the 18-55 lens as well. I just recently purchased an FA 1.4 lens and getting the Bokeh effect is so much easier with that lens. When I shoot at 2.8 or lower (or is it higher? I mean 1.4-2.8) I find it really easy to achieve. Above that, everything remains in focus a little more.
08-09-2011, 11:55 AM   #7
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As a thumb rule, bokeh depends on following things

1) Aperture (Wider the Aperture more bokeh you get)
2) Sensor Size (bigger the sensor size shallower the DOF)
3) Focal length (larger the focal length, crazier it gets)

I dont have fast lens so I use focal length to get shallow DOF. Below shot is taken with kit lens at 200mm

Last edited by Swapnil; 08-09-2011 at 12:42 PM.
08-09-2011, 12:18 PM   #8
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The DA 50-200 is a bokeh machine




08-09-2011, 02:30 PM   #9
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Another factor that influences bokeh is the aperture shape. An aperture with 3 or 4 or 5 iris blades, when stopped-down a bit, can produce jagged nervous bokeh. More iris blades usually give a smoother bokeh. A wide-open aperture is usually pretty round; then the optical design determines whether your bokeh is smooth or nervous or globular or whatever.

As mentioned, you can make bokeh more visible by using a lens with thin DOF. That means using a longer lens, or a faster shorter one. Thin DOF means that only a slim area around your subject is sharp; the rest of the image is OOF, out-of-focus, and hence shows bokeh.

There's an easy way to compare the DOF of various lenses: FL/AP! Divide the focal length by the aperture. The bigger the number, the thinner the DOF. So DOF is about the same with a 200/4 or 100/2 or 50/1. And a dirt-cheap 135/2.8 has thinner DOF than does a rather expensive 50/1.2.

Last edited by RioRico; 08-10-2011 at 12:44 PM.
08-10-2011, 09:46 AM   #10
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Thank you all for your generous inputs.

I am learning to shoot in MF and noticed it is a bit easier to achieve bokeh effect than it is in AF, as reivax pointed out. I am also saving up to buy a faster lens which will give me shallow DOF & more bokeh, as riorico explained nicely
08-10-2011, 01:12 PM - 1 Like   #11
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QuoteOriginally posted by lovejoy Quote
Thank you all for your generous inputs.

I am learning to shoot in MF and noticed it is a bit easier to achieve bokeh effect than it is in AF, as reivax pointed out. I am also saving up to buy a faster lens which will give me shallow DOF & more bokeh, as riorico explained nicely
MF is definitely a challenge when you first start. At first, it was so hard to focus manually, it's gotten a lot easier. I know I still have a long way to go, but I try to practice every chance I get. I end up wasting a lot of space on the memory card, but the great thing is that it doesn't cost you anything to delete the bad pictures to make room for the better ones.

I'm still pretty new to the game and everything you want to do with the camera is a learning process. However, little by little it gets easier. Just read and read and read as much as you can and then shoot and shoot and shoot even more. Trial and error is a great teacher.
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