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Circle of Confusion


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#1 Joachim Imbard

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Posted 10 July 2006 - 12:19 PM

Hi everybody

I try to know what is the circle of confusion of different formats of camera.
I would know what is the CoC for Super8, 16mm and Super 16 and also for new HD formats. I know that the circle of confusion of 35mm is about 0,033mm.

Joachim Imbard
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#2 John Pytlak RIP

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Posted 10 July 2006 - 12:26 PM

Hi everybody

I try to know what is the circle of confusion of different formats of camera.
I would know what is the CoC for Super8, 16mm and Super 16 and also for new HD formats. I know that the circle of confusion of 35mm is about 0,033mm.

Joachim Imbard
joachim.imbard@gmail.com


It really depends on what kind of sharpness requirement you define for the system. Larger formats tend to have larger CoC specified because the required magnification is less:

http://en.wikipedia....le_of_confusion

Do a search:

http://www.cinematog...?showtopic=8853

http://www.cinematog...n...d&pid=54233
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#3 Olex Kalynychenko

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Posted 10 July 2006 - 03:11 PM

Hi everybody

I try to know what is the circle of confusion of different formats of camera.


HI.
Super 8, DS8
russian Quarz 1x8S-2, Quarz 1x8S-XL, Quarz 2x8S-3, user manual, CoC 0.02 mm

16 mm
USSR standard of professional cine cameras - 0.0149 mm
USSR Krasnogorsk-3 camera user manual of Merteor-5 zoom lens
CoC for 17 mm zoom position - 0.018 mm,
CoC for 32 mm and 69 mm zoom position 0.022 mm

USA 0.001' = 0.025mm
Cooke 0.0005' = 0.0127 mm

35 mm cine cameras
USSR standard 0.032 mm
USA 0.002' = 0.05 mm
Cooke 0.001' = 0.025 mm

70 mm cine cameras
USSR standard 0.03 mm
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#4 Jim Murdoch

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Posted 17 July 2006 - 07:42 PM

Hi everybody

I try to know what is the circle of confusion of different formats of camera.
I would know what is the CoC for Super8, 16mm and Super 16 and also for new HD formats. I know that the circle of confusion of 35mm is about 0,033mm.

Joachim Imbard
joachim.imbard@gmail.com

A complication with electronic cameras is that they all require an anti-aliasing optical low-pass filter mounted on top of the imaging chip. The effect of this is somewhat like a slightly out-of-focus video tap camera imaging a film camera ground glass: No matter what you do to the film camera lens, you can never get the video tap sharpness past a certain point.

In the case of a "proper" video camera (HD or otherwise) the anti-alias filter has the effect of "flattening" the circle of confusion.
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#5 Mike Panczenko

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Posted 17 July 2006 - 08:48 PM

In the case of a "proper" video camera (HD or otherwise) the anti-alias filter has the effect of "flattening" the circle of confusion.



What do you mean by "flattening" the CoCs? Do you mean because the anti alias filter degrades the entire image as a whole, the difference between the varying circles becomes less apparent?
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#6 Doug Hart

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Posted 17 July 2006 - 10:19 PM

HI.
Super 8, DS8
russian Quarz 1x8S-2, Quarz 1x8S-XL, Quarz 2x8S-3, user manual, CoC 0.02 mm

16 mm
USSR standard of professional cine cameras - 0.0149 mm
USSR Krasnogorsk-3 camera user manual of Merteor-5 zoom lens
CoC for 17 mm zoom position - 0.018 mm,
CoC for 32 mm and 69 mm zoom position 0.022 mm

USA 0.001' = 0.025mm
Cooke 0.0005' = 0.0127 mm

35 mm cine cameras
USSR standard 0.032 mm
USA 0.002' = 0.05 mm
Cooke 0.001' = 0.025 mm

70 mm cine cameras
USSR standard 0.03 mm


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#7 Doug Hart

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Posted 17 July 2006 - 10:35 PM

Hi -

Every 1st AC does it differently, and every chart and calculator (and lens manufacturer) uses a different Circle of Confusion.
As a long-time 1st AC, I have my own preferences for settings, which I have used successfully for years:

16mm (& Super 16mm) 1/1000" ( 0.001")

35mm for TV (TV Series, Commercials) 1/500" ( 0.002") (for a small TV screen)
35mm for Theatre (Feature Films) 1/700" ( 0.0014") (for a large theatre screen)
35mm Anamorphic (Feature Films) 1/1000" ( 0.001") (for a larger theatre screen)

These are based on negative size, degree of magnification needed, and looking at the results on screen.
Other 1st ACs use different values, based on THEIR experience.

No set of values is absolutely RIGHT and not set is absolutely WRONG.
They are just guidelines, and based on personal preferences.

Take a close look at the Depth of Field charts and calculators you use. You will be surprised to see how many different Circles of Confusion are used, and how they change year to year.

This is discussed in greater detail in my book THE CAMERA ASSISTANT: A COMPLETE PROFESSIONAL HANDBOOK, Focal Press, 1996.

Doug Hart
1st AC, New York
Author, Teacher
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#8 Jim Murdoch

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Posted 18 July 2006 - 02:37 AM

What do you mean by "flattening" the CoCs? Do you mean because the anti alias filter degrades the entire image as a whole, the difference between the varying circles becomes less apparent?

The action of an optical low-pass filter (LPF) is somewhat hard to explain. If you put an ordinary diffusion filter over any image, sharp or blurry, you will see a difference. With an optical LPF on the other hand, held over a soft image, it will look like a clear piece of glass, while held over a sharply-defined image, it will make it look softer. It acts like a softening filter that only works on details above a certain "fine-ness".

So if you interpose that between an lens and say, a piece of film, you will only be able to focus the image on the film up to the sharpness permitted by the optical LPF. There will be two points on the focus ring where maximum sharpness is obtained, rotating it through the region in between will make no visible difference to the focus. This is what I meant by "flattening" the Circle of Confusion.
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