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Bokeh Advice

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anjz

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I recently bought a depth of field calculator. Until I bought it, the rules I used were: Buy really fast glass for portraits. If very close to my subject (maybe 3-5 feet or so), use 2.8 aperture on my 50mm. If a little further away, use f/2 or 1.4. That's as scientific as I got and the results were basically fine--well, sort of, but I wished for more control.

So, after I got my DOF calculator (for iPhone), I started doing some calculations. It appeared that I could, in fact, stand at 3 feet from my subject and shoot at f/8 and still knock my backgrounds out of focus and, at the same time, keep more of my subject in focus.

Tried to test my new-found knowledge and discovered that, standing 3 feet away from my subject and shooting 2 nearly identical shots at f/2.8 and f/8, the background blur was much stronger with at f/2.8. This is even though the background was "at least" 4 feet away from my subject and the DOF for both f/2.8 and f/8 were in the inches...not feet. Going to redo the test with the background considerably farther away (distance between subject and background much further than focal-plane to subject distance), but not anticipating vastly different results.

So, it looks like I need to go back to my original rules (use 1.4, 2 and 2.8 exclusively for portraits...regardless of what some calculator says).

So, here's my question: what have you found? Are most of you isolating subjects at only the widest apertures, or is there some way to use smaller apertures at close distances to subjects?

Posted 3 years ago #
towen7

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The DOF calculator can't know the quality of the bokeh of your particular lens. Sure backgrounds at 7' are out of focus when your subject is 3' from the focal plane at f/8, but how far out of focus and the quality of that "blur" isn't the same as it is at f/2.8.

Posted 3 years ago #
anjz

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Yes, the obviousness of this just sort of hit me. Alright, thank you.

Posted 3 years ago #
spraynpray

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towen7 said:
The DOF calculator can't know the quality of the bokeh of your particular lens. Sure backgrounds at 7' are out of focus when your subject is 3' from the focal plane at f/8, but how far out of focus and the quality of that "blur" isn't the same as it is at f/2.8.

Can you please explain to a noobie what affects the bokeh if the lenses used are similar length and aperture please?

Posted 3 years ago #
noxin

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I think a lot will depend on the focal length of the lens, but that should show up in the calculations. In my opinion, a lot depends on the 'details' or small differences in lens itself (ie number of and design of the glass elements, number of blades, etc). I have 3 lenses (a wide angle zoom, telezoom, and prime) that fall close to 80mm. I bet if I took the same picture with all three there would be slight difference in bokeh between them. I haven't tested it, but it's a gut call I get from using them.

Posted 3 years ago #
anjz

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That's my understanding, as well. Lens manufacturers sometimes use curved aperture blades, increase the number of blades, and choose certain glass elements, to help increase the pleasantness of out-of-focus light discs in photographs taken with certain lenses.

f you have, for example, relatively less aperture blades, then the aperture opening will look less like a circle and more jagged, and the resulting light discs will not be perfectly round. More blades, and curved blades, will increase the smoothness (the "circularness") of the aperture opening and make out of focus light appear more smooth and circular in photos taken with such a lens.

Note also that a wider aperture will defocus backgrounds more than a stopped-down aperture (that's what I failed to consider before posting the original question). So, given the same scene, and the same lens, the wider aperture will blur the background more than that lens stopped-down. This analysis falls apart a little as the focal plane-to-background distance gets larger. Then, the physical diameter of the aperture will determine background blur. Basically, the f stop determines the blur of relatively close backgrounds and the actual physical size of the aperture will determine the blur of distant background.

Posted 3 years ago #
anjz

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Bob Atkins says it better than I did. Here's a link to his Bokeh page: http://www.bobatkins.com/photography/technical/bokeh_background_blur.html

Posted 3 years ago #
towen7

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spraynpray said:
Can you please explain to a noobie what affects the bokeh if the lenses used are similar length and aperture please?

Sperical aberration, the number and shape of the iris blades, vignetting, contrast...
Here are a couple of explanations that are better than what I could write.

Here is a basic article about Bokeh from Ken Rocklwell
http://www.kenrockwell.com/tech/bokeh.htm

And here is a much, much more thorough explanatio from Zeiss
http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_35_Bokeh_EN/$File/CLN35_Bokeh_en.pdf

Posted 3 years ago #
spraynpray

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Thanks guys, that is helpful.

Posted 3 years ago #
NikoDoby

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Anjz, you do understand that Bokeh is not the same thing as Depth of Field right? They are two separate things.

Posted 3 years ago #
clillja

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And don't forget that VR affects bokeh - makes it worse - "busier" as Thom H. says. Another reason to think they may leave it out of the upcoming 85/1.4.... Makes sense - actually moving an element or group around during exposure is going to add an asymmetrical element to the bokeh signature.

Posted 3 years ago #
anjz

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Yes, I know they are different. Sorry if that wasn't clear from the above. Frankly, my post was ill-conceived from the get-go. I was excited with the idea of reducing my daily gear bag by 2 lenses (my 35 f/2 and my 50 f/1.4), and jumped the gun after I played with the DOF calculator for a while....damn, I didn't even have any beer before I posted..no excuses :)

Posted 3 years ago #
SquamishPhoto

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-

Posted 3 years ago #
SquamishPhoto

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If you want to do a good job throwing the background out of focus at f8 then buy a 300mm.

Posted 3 years ago #
studio460

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anjz said:
So, here's my question: what have you found? Are most of you isolating subjects at only the widest apertures, or is there some way to use smaller apertures at close distances to subjects?

There are five variables which affect the degree of "bokeh:"

1. Aperture: the larger the aperture (numerically, lower, e.g., f/1.4), the less depth-of-field, and the greater the bokeh effect.
2. Field-of-view (angle-of-view): the narrower your angle-of-view (i.e., the more telephoto), the shallower the apparent depth-of-field, and the more pronounced the bokeh effect will be.
3. Size of image sensor: the larger the sensor, the shallower the apparent depth-of-field, and the greater the amount of bokeh.
4. Distance: A. Focal plane-to-subject distance: the shorter the focused distance is to your subject, the greater the amount of bokeh effect on your background.
5. Distance: B. Subject-to-background distance: the further away your background is from your subject, the more pronounced the bokeh is on your background.

You can employ any or all of these techniques to maximize the bokeh effect on your background. For example, say you don't have the budget for that fancy 300mm f/2.8, but what you do have is a 300mm or 400mm f/5.6, maximum-aperture zoom. In this case, you can exploit the telephoto lens' inherent, narrow angle-of-view, use close-focus technique, and choose a really, really far away background to maximize the bokeh effect, even though its maximum aperture isn't that large (see examples, below).

Exaggerated bokeh due to distant background:

AF VR Nikkor 80-400mm f/4.5-5.6G: 400mm @ f/5.6 w/VR.

Exaggerated bokeh due to close-focus:

AF VR Nikkor 80-400mm f/4.5-5.6G: 400mm @ f/5.6 w/VR.

Exaggerated bokeh due to large aperture:

AF Nikkor 85mm f/1.4D @ f/1.4.

Posted 3 years ago #
studio460

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spraynpray said:
Can you please explain to a noobie what affects the bokeh if the lenses used are similar length and aperture please?

All else being equal, two different lenses at identical focal lengths, at identical apertures, will have similar amounts of bokeh (e.g., the amount bokeh of a 70-200mm f/2.8 lens zoomed to 180mm, will be the same as a fixed-focal length 180mm f/2.8 lens, when both are set at f/2.8). Variances in diaphragm design may affect the character of the bokeh, but the amount of bokeh will be about the same.

An exception to this would be Nikon's "de-focus control" lenses, the DC-Nikkor 105mm and 135mm, which are specialty lenses that enable manual control over the lens' degree of spherical aberration, which affects the amount of deliberately introduced foreground and background bokeh.

Posted 3 years ago #
spraynpray

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studio460 said:
All else being equal, two different lenses at identical focal lengths, at identical apertures, will have similar amounts of bokeh (e.g., the amount bokeh of a 70-200mm f/2.8 lens zoomed to 180mm, will be the same as a fixed-focal length 180mm f/2.8 lens, when both are set at f/2.8). Variances in diaphragm design may affect the character of the bokeh, but the amount of bokeh will be about the same.

That's what I thought too. Thanks for clarifying it studio460.

Posted 3 years ago #
adamz

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studio - don't confuse bokeh with DOF!!!!

Posted 3 years ago #
studio460

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adamz said:
studio - don't confuse bokeh with DOF!!!!

Why would you think I've confused them? The terms used in these posts should be clear in the context of this thread. The term "bokeh" is used to describe the imaging characteristics of out-of-focus areas. Images employing shallow depth-of-field tend to have more out-of-focus areas. Bokeh is the result of any one of several variables, one of which is, shallow depth-of-field. Clear enough?

Posted 3 years ago #
adamz

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I know what bokeh is, although when I read that "... two different lenses at identical focal lengths, at identical apertures, will have similar amounts of bokeh..." I want to make sure, that other users on this forum will not take such a shortcut, as this what You are referring to is not bokeh itself but clearly it's DOF. To elaborate this a little bit more, each lens has it's own unique bokeh (out of focus rendering) and two different lenses that covers exactly the same focal length and exactly the same apertures (i.e. nikon 70-200/2.8 and sigma 70-200/2.8, nikon 50/1.4 and sigma 50/1.4) will render the out of focus areas in a different way.

Posted 3 years ago #
studio460

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adamz said:
To elaborate this a little bit more, each lens has it's own unique bokeh (out of focus rendering) and two different lenses that covers exactly the same focal length and exactly the same apertures (i.e. nikon 70-200/2.8 and sigma 70-200/2.8, nikon 50/1.4 and sigma 50/1.4) will render the out of focus areas in a different way.

I think you're splitting hairs here. As I said, given the same focal length and aperture, generally speaking, the amount of bokeh (or, to avoid any "confusion," in other words, "the relative sizes of the circles-of-confusion resolved from the images' out-of-focus areas") will be similar in degree.

For example, in the two images shown below, the amount of bokeh appears nearly identical (even the character of the bokeh happens to be virtually indistinguishable in this example). Even If each lens' bokeh is "unique," I would be hard-pressed to tell which lens shot which, or if both were shot with the same lens, without checking the EXIF data. I would be interested to see the differences between the Nikon and Sigma lenses you suggested.

AF Nikkor 80-200mm f/2.8D ED: 200mm @ f/2.8

AF Nikkor 180mm f/2.8D ED: 180mm @ f/2.8

Posted 3 years ago #
shivaswrath

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alls I know is I love my 700-200 VRII bokeh :-)

just posted this one up from a shoot a month ago (back log):

Posted 3 years ago #
kyoshinikon

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Bokeh Advice?

Don't get a reflex lens "smirk"...

I one with you shivaswrath: both the 70-200mm f/2.8 and the 80-200mm f/2.8 have lovely bokeh...

Does anyone have a shot from the 135mm f/2 to show?

Posted 3 years ago #
foofiebeast

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studio460 said:
(even the character of the bokeh happens to be virtually indistinguishable in this example). Even If each lens' bokeh is "unique," I would be hard-pressed to tell which lens shot which, or if both were shot with the same lens, without checking the EXIF data. I would be interested to see the differences between the Nikon and Sigma lenses you suggested.

while this may be true for some cases, you can't argue that lenses don't have different bokeh. while sometimes it's similar, other times it's pretty obvious. An unfair example would be as kyoshinikon just mentioned a mirror reflex lens which will leave you with that, well some say "distracting" donut bokeh, although some people like it.
such as this http://www.flickr.com/groups/bokeh_/discuss/72157604545634741/ (which i believe someone has posted on the forum as an example before as well)

that being said,there is a huge difference in the quality and shape of the bokeh between my lenses. I may be wrong, but this is my guess. Over time as we have stepped into the digital age bokeh amongst lenses has probably gotten much more similar. The majority of my lenses are from all over the years and I mainly shoot with film. The bokeh between these lenses is pretty radically different. Correct me if I'm wrong but the bokeh has mostly to do with aperture blades and their shape correct? I assume modern lenses are all pretty similar, while older ones probably had more variety. Let me end with saying I have no idea if thats true, haha, just guessing.

Posted 3 years ago #
heartyfisher

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Sigh.. I have been keeping away from this discussion,,but I guess I finally have to .. I think I know what bokeh is and well because it is not the same as what many of you are saying I think I may be wrong.. anyway

I think bokeh is not just the shape of the out of focus points of light. which is circular or pentagon depending on the shape of the aperture.

Bokeh is not DOF, DOF is the amount of area that is in focus.

Bokeh is feel and nature of the out of focus points of light. The best bokeh looks like what you get when you take a white circle on a black background and apply a fair amount of gausian blur to it.

Some good and modern lenses have a nice round white disk for the out of focus points of light. This results in good bokeh(but not the best).

Many of the modern zoom lenses with long ranges like my 18-200VR has really bad bokeh at most focal lengths. The out of focus points of lights looks like several concentric rings of light. with weird radiating bands as well.

Wide aperture Lenses with F1.0 to F1.2 usually have bad bokeh due to the corrections needed for sharpness by the aspherical elements.

Posted 3 years ago #