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05-29-2012, 09:38 AM   #61
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QuoteOriginally posted by Anvh Quote
* Bokeh (as mentioned) depends on lens design, aperture size and position within the lens, number and shape of iris blades
If you're talking about OOF then yes you're correct but not when we talk about Bokeh.
It's in the first 2 chapters and i can present you with more studies if you want.

* A fast wide-aperture lens may or may not have 'better' bokeh. But a wide aperture means more if the image will be OOF than with a tighter aperture. Its bokeh may be more visible. What you *do* with those OOF areas is up to you.
You're forgetting so much here but you corrected that later so no comment there but i thought you would find for example Figure 4. very interesting.
Not to add fuel to the fire, but isn't bokeh, as a term, used to relate to all the out of focus (i.e. blurred) portions of the image? That is the definition used in Wikipedia, specifically all the blurred areas of the image outside the depth of field.

If this is the definition then all aspects of the lens including the diaphram shape MUST be considered, because this shape only appears in areas outside the DOF, Inside the DOF the aperture appears as a point After all, that is the definition of depth of field in the first place, the range of distance from in front of the plane of focus to the distance behind the plane of focus, where the image is acceptably sharp, or in specific mathematical terms, where the circle of confusion on the image as viewed in final form is less than 0.01 inch or 0.25mm. (this is the diameter of the Circle of Confusion when the 20 micron CofC at the sensor level is enlarged to a standard 8x10 inch print)

05-29-2012, 10:10 AM   #62
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QuoteOriginally posted by Lowell Goudge Quote
Not to add fuel to the fire, but isn't bokeh, as a term, used to relate to all the out of focus (i.e. blurred) portions of the image? That is the definition used in Wikipedia, specifically all the blurred areas of the image outside the depth of field.

If this is the definition then all aspects of the lens including the diaphram shape MUST be considered, because this shape only appears in areas outside the DOF, Inside the DOF the aperture appears as a point After all, that is the definition of depth of field in the first place, the range of distance from in front of the plane of focus to the distance behind the plane of focus, where the image is acceptably sharp, or in specific mathematical terms, where the circle of confusion on the image as viewed in final form is less than 0.01 inch or 0.25mm. (this is the diameter of the Circle of Confusion when the 20 micron CofC at the sensor level is enlarged to a standard 8x10 inch print)
Well in "mathematical" terms bokeh is convolution between the aperture and the image where things more out of focus are more "convoluted" with the aperture. In practical terms it is most visible with the pointy light sources in high contrast images. If we have a round aperture, than every point is going to look like a circle. If the lens used is mirror telephoto, then the bokeh looks like rings. Actually you can get bokeh to have any shape you like by cuting a piece of cardboard or something like it and placing it right in front of the lens.

Here is an example I found on flickr:



And here is link to more "scientific" or technical explanation and example with triangular bokeh:
http://www.trenholm.org/hmmerk/ATVB.pdf
05-29-2012, 10:23 AM   #63
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By some yes it is but that isn't the official meaning.
Beside that out of focus blur is all that we call that is not "sharp" enough because of the size of the CoC it's not called bokeh.
Bokeh is purely the character so to say of the blur and that's for 99% defined by the light distribution inside the CoC (blur disk /spots) when we are talking about photography with normal lenses and normal kind of apertures so not funny shaped ones or very low numbers ones like 3 blades for example.

Just look up photos taken with the DfA100 and the DFA 100 WR, the WR has rounded blades and the normal has straight blades, good luck finding difference in the blur besides the highlights shapes.
Therefore the effect aperture blades have on the bokeh is very highly overrated, the lens design is what does almost all the work.


this a good visual explanation what is going on with Bokeh.
http://bokehtests.com/Site/About_Bokeh.html

and if you want a more technical explaination, Carl zeiss has a nice PDF
http://www.zeiss.com/c12567a8003b8b6f/embedtitelintern/cln_35_bokeh_en/$file/cln35_bokeh_en.pdf

What you want to read is The Nature of Blurriness

QuoteQuote:
There is a particularly interesting point further to the left in the graphic above, about 0.4 mm in front of the focal point of the paraxial rays: there, the marginal rays seem to overtake those travelling more on the inside. The light cone is no longer ideally arranged, and we could say that the rays of light are "confused."
This is the original meaning of the Japanese word "bokeh."
There are so many rays that overlap in this zone of intersection that a ring with increased brightness results. This means that the circle of confusion is not a disk with homogenous brightness.

There are no rays that intersect or overlap behind the focal point. Quite the opposite; the density of the rays on the outside is somewhat less than in the ideal geometric light cone. The circle of confusion is therefore larger behind the focal point than in geometric theory, and the brightness decreases moving outward from the inside, while the circle is smaller in front of the focal point and is clearly bordered by a bright ring around the outside.
On

Last edited by Anvh; 05-29-2012 at 10:43 AM.
05-29-2012, 10:51 AM   #64
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QuoteOriginally posted by Anvh Quote
* Bokeh (as mentioned) depends on lens design, aperture size and position within the lens, number and shape of iris blades
If you're talking about OOF then yes you're correct but not when we talk about Bokeh.
It's in the first 2 chapters and i can present you with more studies if you want.
It seems that your criticism is that aperture design affects OOFH (out-of-focus highlights) but that OOFH aren't precisely within the realm of the Japanese "spirit of bokeh". Yet earlier, the author says that bokeh IS a function of aperture design as well as optical design and other factors. And OOFH are certainly a component of what we think of as bokeh, even if not an exact translation from Japanese. So I won't worry about this. In fact, I'll expand my statement above:

* Bokeh (as mentioned) depends on lens design and aberrations, aperture design (size and position within the lens, number and shape of iris blades), [and the other factors I mentioned, and maybe more]

QuoteQuote:
* A fast wide-aperture lens may or may not have 'better' bokeh. But a wide aperture means more if the image will be OOF than with a tighter aperture. Its bokeh may be more visible. What you *do* with those OOF areas is up to you.
You're forgetting so much here but you corrected that later so no comment there but i thought you would find for example Figure 4. very interesting.
It seems your criticism here is that I didn't originally mention lens aberrations as a factor. My list of factors wasn't exhaustive, and I sometimes don't remember and sometimes don't want to bother listing all the factors, which is why I say "and other factors".

I also didn't list all possible factors in the presentation and perception areas of DOF, like whether a picture is displayed where it can be seen or whether the intended audience even gives a rat's ass about the picture, or if they're vision-impaired. Presentation and perception are just as important as the photographic components. Your author didn't address these in the articles you linked. Tsk.

05-29-2012, 11:05 AM   #65
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QuoteOriginally posted by RioRico Quote
It seems that your criticism is that aperture design affects OOFH (out-of-focus highlights) but that OOFH aren't precisely within the realm of the Japanese "spirit of bokeh". Yet earlier, the author says that bokeh IS a function of aperture design as well as optical design and other factors. And OOFH are certainly a component of what we think of as bokeh, even if not an exact translation from Japanese. So I won't worry about this. In fact, I'll expand my statement above:

* Bokeh (as mentioned) depends on lens design and aberrations, aperture design (size and position within the lens, number and shape of iris blades), [and the other factors I mentioned, and maybe more]
I'll quote it for you so you can read it again, i'll highlight some things to make it easier for you.

QuoteQuote:
Characterization of the blur disk

Since any image is represented by a large number of images of points, we may attempt to understand the whole by considering the blurring of a single point. An unsharply imaged point is associated with a circle of confusion, or a blur disk. This blur disk is characterized by
A size.
A shape.
The light distribution across the disk.

The size of the disk determines the "amount of blur". The shape of the blur patch does not need to be circular, in which case the designations "circle of confusion" or "blur disk" are misnomers. Nonetheless, for convenience the word disk will be freely used to mean a patch of arbitrary shape. Although the size and the shape of the disk are unmistakable blur characteristics, they do not touch the essence of bokeh as the Japanese intended the word. The distribution of light across the disk does. However, the distinction is not always clear and what follows is intended as an overview of a variety of factors that influence the rendering of OOF image parts. Explanations of the underlying mechanisms will be brief and the reader is referred to other pages for elaborateness.



QuoteOriginally posted by RioRico Quote
It seems your criticism here is that I didn't originally mention lens aberrations as a factor. My list of factors wasn't exhaustive, and I sometimes don't remember and sometimes don't want to bother listing all the factors, which is why I say "and other factors".

I also didn't list all possible factors in the presentation and perception areas of DOF, like whether a picture is displayed where it can be seen or whether the intended audience even gives a rat's ass about the picture, or if they're vision-impaired. Presentation and perception are just as important as the photographic components. Your author didn't address these in the articles you linked. Tsk.
It's in the second chapter... Depth of field
QuoteQuote:
Viewing conditions

There is a difference between calculated sharpness and perceived sharpness. For the perceived or apparent depth of field, the lighting conditions are important, as a well-illuminated print will more easily reveal imperfections than the same print in a dim room. Further, an observer with a high visual acuity may reject a print that satisfies another observer with poor vision. A very important factor is the viewing distance in relation to the size of the photograph. Obviously, a large print viewed from close is much more demanding than a small print viewed from a large distance. Within the concept of DOF it is usually assumed that the print viewing distance does not depend on the picture taking lens. There is a good reason for this, for most people do not change seats during a slide presentation and at an exposition they examine the various photographs from similar distances. The concept of DOF is adapted to these habits, since the DOF scales imprinted on lenses are based on a sharpness criterion that does not depend on the focal length. Likewise, a typical DOF calculator will suggest—or may even impose—a sharpness criterion based on the film format, independent of the lens focal length. Bear in mind, however, that many of the conclusions reached in the remainder of this article would be different if we had assumed 'perspectively correct' viewing, i.e. a viewing distance in proportion to the focal length.

More complains?

ps. don't get mad at me now, you said you had read it and you're complain directly about it so it's only good to directly quote things.
05-29-2012, 11:49 AM   #66
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#1:
QuoteQuote:
Although the size and the shape of the disk are unmistakable blur characteristics, they do not touch the essence of bokeh as the Japanese intended the word. The distribution of light across the disk does.
Maybe they're not of the Japanese essence of the word (simple-minded, IIRC), but they're certainly in the common understanding of bokeh. Dismissed.

#2: Maybe you should highlight what you think is important or discordant here. I don't see how the quoted passage conflicts with what I wrote. Cheers!
05-29-2012, 03:25 PM   #67
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This is artwork as far as I am concerned.

If its got sufficient blurriness where I want blurriness and that blurriness looks cool and makes the image better that's good enough for me.

Nit picking about what to call it is counter productive. How to make it happen with various lenses and how to create certain effects IS productive.
05-29-2012, 03:29 PM   #68
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Blurry in the front, focused in the middle, blur in the back...front blur---back blur... doesn't matter. Its all blur.

How to create a 6 inch deep depth of field and make a killer image using that knowlege is good....

Nitpicking over the technical term of 'blur' kind of deviates from the intent of the post.

05-29-2012, 04:33 PM   #69
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05-29-2012, 04:48 PM   #70
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QuoteOriginally posted by Paleo Pete Quote
Can I go to the bathroom?
That's probably a good idea.
05-31-2012, 10:03 AM   #71
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QuoteOriginally posted by RioRico Quote
#1:

Maybe they're not of the Japanese essence of the word (simple-minded, IIRC), but they're certainly in the common understanding of bokeh. Dismissed.

#2: Maybe you should highlight what you think is important or discordant here. I don't see how the quoted passage conflicts with what I wrote. Cheers!
Common western use might be worded better, but still even then the aperture blades only do so much the lens design is far more important for the character of the blur.
Saying you get better OOF blur because a lens have more blades or are more rounded is purely a market "stunt".

#2 here is the quote, with the highlight what is important and why i quoted the part of the article.
QuoteQuote:
I also didn't list all possible factors in the presentation and perception areas of DOF, like whether a picture is displayed where it can be seen or whether the intended audience even gives a rat's ass about the picture, or if they're vision-impaired. Presentation and perception are just as important as the photographic components. Your author didn't address these in the articles you linked. Tsk.
Obviously he did.
05-31-2012, 10:06 AM   #72
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QuoteOriginally posted by alamo5000 Quote
Blurry in the front, focused in the middle, blur in the back...front blur---back blur... doesn't matter. Its all blur.

How to create a 6 inch deep depth of field and make a killer image using that knowlege is good....

Nitpicking over the technical term of 'blur' kind of deviates from the intent of the post.
It's the same that saying it doesn't matter what colour it is as long as it is a colour it's alright but we all know it isn't that simple.


And how we call something and what we mean with it is important for communication.
bokeh often means something else then out of focus blur, it might be better not to use bokeh at all if you ask me...
05-31-2012, 10:45 AM   #73
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QuoteOriginally posted by Anvh Quote
It's the same that saying it doesn't matter what colour it is as long as it is a colour it's alright but we all know it isn't that simple.


And how we call something and what we mean with it is important for communication.
bokeh often means something else then out of focus blur, it might be better not to use bokeh at all if you ask me...
Gee, does this mean we abandon the adaption of the original Japanese word because with all the wonderful words we have in the English language, we can't come to an agreeable definition of what the word we adapted due to lack of a suitable word, really should mean in the first place

It sounds like we have gone in a full circle
05-31-2012, 12:22 PM   #74
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QuoteOriginally posted by Lowell Goudge Quote
Gee, does this mean we abandon the adaption of the original Japanese word because with all the wonderful words we have in the English language, we can't come to an agreeable definition of what the word we adapted due to lack of a suitable word, really should mean in the first place

It sounds like we have gone in a full circle
We have enough words for the blur
- out of focus blur
- defocus aberration
- defocus blur
And you know precisely what i mean with this right, at least with the first and the last one.

With bokeh we are stuck with the original meaning and the meaning people have given it over time (most likely due to misunderstanding), both are valid in their own way but since we already have words for the blur then why must we use bokeh for that as well.
Does it sound more interesting that way?
05-31-2012, 01:11 PM   #75
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QuoteOriginally posted by alamo5000 Quote
I have seen some lenses that have apertures from 1.4....some with 1.7...some with 2.4 and so on and so forth...assuming focal length is standard really what would be the 'big difference' between a 1.4 and 1.7 and 2.4 or so on and so forth?
Well, one thing is for sure... with faster lenses it is easier to start an argument over the definition of bokeh...

QuoteOriginally posted by Anvh Quote
Does it sound more interesting that way?
Luckily, I'm still new enough that I can still impress my friends with words and phrases like "aperture" and "depth of field".

As for the original post... my 2 cents:

A larger aperture gives you the ability to let in more light, faster than a smaller one. This is useful for the subject isolation and out-of-focus background reasons mentioned. It is also useful when shooting fast moving things in low light. Fast moving requires fast shutter speed which reduces the amount of time light can hit the sensor. Your options are to make the sensor more sensitive to light by upping the ISO which creates noise in the image or use a larger aperture so that more light gets in faster.

As others have mentioned, in general, lenses will be sharper when stopped down a little from their widest setting. However, whether a particular f/1.4 lens will be sharper at f/2 than some other f/1.8 lens at f/2 is really up to the lens. For this reason, I highly recommend consulting the lens reviews on this forum often. It will be those reviews and viewing sample images shot with the lenses in question that will help you decide which lenses are right for you. Even when it comes to (and I hate to say it) bokeh. Hopefully most will agree that it is subjective and what I prefer, you may not. Or like Rio Rico, you'll learn the characteristics of several lenses and select the one that can create the image you're going for.

The other alternative is LBA. Just buy a dozen lenses, shoot with them all and then sell off the ones you're not using. If you're careful about buying, they really don't depreciate much (if at all). However, the drawback is that selling them is easier said than done. I can personally attest that this method is highly educational though. However, as I am also on a budget, I mostly avoid eBay and instead frequent garage sales, estate sales, goodwill and pawn shops. I have found that pawn shops (at least by me) price their lenses based on mass. That is to say that big heavy lenses are $100 or more and small lenses are $20 or less. This works great when shopping for fast 50mm and/or close focusing 28mm lenses!

Ok, so that was maybe 4 cents worth. But from one newbie to another, there ya go.
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