THE PAVILION ANNEX

General discussions of interest to readers and fans of Harlan Ellison.

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diane bartels
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Re: THE PAVILION ANNEX

Postby diane bartels » Sat Nov 01, 2014 8:38 am

Hi Frank. How are you?

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FrankChurch
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Re: THE PAVILION ANNEX

Postby FrankChurch » Sat Nov 01, 2014 11:53 am

Stay warm Diane. brrr

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Rick Keeney
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Re: THE PAVILION ANNEX

Postby Rick Keeney » Mon Nov 03, 2014 6:21 am

Barber,

A friend of mine on FB asks..."ANy photography experts in here? i've been reading all the pertinent wikipedia articles but i still don't understand *why* a smaller aperture gives you greater depth of field. anybody can explain it simply enough that even collins can grok?"

Mark Tiedemann
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Re: THE PAVILION ANNEX

Postby Mark Tiedemann » Mon Nov 03, 2014 8:50 am

Lemme think about that question. Thirty years ago I could have explained it on a piece of paper with diagrams, but today...?

Meantime, something for your consideration: http://marktiedemann.com/wordpress/?p=2370

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FrankChurch
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Re: THE PAVILION ANNEX

Postby FrankChurch » Mon Nov 03, 2014 11:26 am

According to the Farmer's almanac Southern California is going to have a warmer winter. Bastards. :)

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AndrewR
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Re: THE PAVILION ANNEX

Postby AndrewR » Mon Nov 03, 2014 12:59 pm

Rick Keeney wrote:Barber,

A friend of mine on FB asks..."ANy photography experts in here? i've been reading all the pertinent wikipedia articles but i still don't understand *why* a smaller aperture gives you greater depth of field. anybody can explain it simply enough that even collins can grok?"


Well, the Wikipedia entry says this (relevant passage is in bold) : "Reducing the aperture diameter (increasing the f-number) increases the DOF because the circle of confusion is shrunk directly and indirectly by reducing the light hitting the outside of the lens which is focused to a different point than light hitting the inside of the lens due to spherical aberration caused by the construction of the lens; however, it also reduces the amount of light transmitted, and increases diffraction, placing a practical limit on the extent to which DOF can be increased by reducing the aperture diameter."

One need only look at a pinhole camera to see this demonstrated. A pinhole camera (or lens-less camera) uses a very small aperture instead of a lens. The interesting thing with pinholes is that they are (roughly) equally "sharp" from zero to infinity. Here are some examples: https://www.flickr.com/groups/wpd/

Of course it's not just the diameter of your aperture that changes the DOF, you also have to consider the focal length of the lens and the size of your recording media. The smaller the sensor (or frame of film), the broader your DOF will be for a given aperture and focal length.

Hope this helps :-)
Andrew Rogers

"Anything more than 500 yds from the car just isn't photogenic." - Brett Weston

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Rick Keeney
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Re: THE PAVILION ANNEX

Postby Rick Keeney » Mon Nov 03, 2014 1:39 pm

Mark Tiedemann wrote:Lemme think about that question. Thirty years ago I could have explained it on a piece of paper with diagrams, but today...?

Meantime, something for your consideration: http://marktiedemann.com/wordpress/?p=2370


Yes, please let me know; once the thinking's over.

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Rick Keeney
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Re: THE PAVILION ANNEX

Postby Rick Keeney » Mon Nov 03, 2014 1:46 pm

Also, Mark. Do you know a Webderlander and Blue Monkey named David Silver?

This is his:

http://www.well.com/user/silver/

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FrankChurch
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Re: THE PAVILION ANNEX

Postby FrankChurch » Mon Nov 03, 2014 7:24 pm

This is easily the greatest quote in world history:

"I am no social scientist."

Ted Bundy.

Mark Tiedemann
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Re: THE PAVILION ANNEX

Postby Mark Tiedemann » Tue Nov 04, 2014 6:56 am

Rick Keeney wrote:Also, Mark. Do you know a Webderlander and Blue Monkey named David Silver?

This is his:

http://www.well.com/user/silver/


Heard the name, but I do not know him. Looks very cool.

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Rick Keeney
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Re: THE PAVILION ANNEX

Postby Rick Keeney » Tue Nov 04, 2014 8:04 am

Nice guy, and smart, this David Silver. And apparently the least attractive man in science fiction.

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Lori Koonce
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Re: THE PAVILION ANNEX

Postby Lori Koonce » Tue Nov 04, 2014 11:18 am

David and I live in the same city, and I'm proud to give him a ringing endorsement as both a collector of vintage cameras and an all around decent human being.

Mark Tiedemann
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Re: THE PAVILION ANNEX

Postby Mark Tiedemann » Tue Nov 04, 2014 11:37 am

The best description of depth-of-field is still to be found in Ansel Adams's Camera and Lens. But to paraphrase, there is a relationship between the film plane (the surface of the film perpendicular to the light entering the lens and striking it) and what is called the circle of confusion, which basically described everything before and behind the point of focus on the film plane. Imagine a point at the center of a circle, the size of the circle determined by the aperture of the lens. (This size and "f-stop" is determined also by the focal length of the lens, so that the longer the lens, the larger the circle at maximum aperture, hence a shallower depth-of-field.)

As you "stop down" to smaller and smaller apertures, that point expand in proportion to the number of circles, in a line, reaching from the rear element of the lens to the film plane. These circles effectively reduce the circle of confusion, channeling the light into a tighter and tighter bundle which is, so to speak, more inclusive in terms of what is sharp before or after the point of focus. It "deepens" the effective area of the film plane. Each f-stop smaller eliminates another range of the circle of confusion, so the film "sees" more clearly before and behind the point of focus.

Hope this helps a bit.

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Steve Barber
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Re: THE PAVILION ANNEX

Postby Steve Barber » Tue Nov 04, 2014 6:46 pm

Rick Keeney wrote:Also, Mark. Do you know a Webderlander and Blue Monkey named David Silver?

This is his:

http://www.well.com/user/silver/


David is a friend, a good guy, a mensch and every other word I can toss at him. And yes, the ugliest man in Science Fiction. So he says, so who am I to disagree?

I'm a little late to the party on the aperture thing, but think of tit this way: The less light gets in through the aperture, the longer it takes to make the image. Since this understandably results in more light from all distances from the lens, they have the opportunity to "define" themselves more completely in the overall image. The more light you let in, the faster the image is made, and the less time the out-of-focus areas have to refine their image.

That's in about as simple English as I can put it. Mark's and Andrew's are the technically accurate explanations, but are more technical in their language and may not satisfy the need for an English explanation.
All I need is a change of clothes, my Nikon, an open mind and a strong cup of coffee.

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Steve Barber
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Re: THE PAVILION ANNEX

Postby Steve Barber » Tue Nov 04, 2014 6:48 pm

FrankChurch wrote:According to the Farmer's almanac Southern California is going to have a warmer winter. Bastards. :)


I don't mind warm, I just need wet!!!

(Stop sniggering...)
All I need is a change of clothes, my Nikon, an open mind and a strong cup of coffee.


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