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Sensor/ Film size and depth of field


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#1 Mathew Collins

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Posted 18 June 2017 - 12:57 AM

Hi,

 

Is there any relationship between Sensor/Film size and depth of field?

 

The following video says, Sensor size has an effect on the depth of field.

 

 

-Mathew Collins.


Edited by Mathew Collins, 18 June 2017 - 01:03 AM.

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#2 Mathew Collins

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Posted 18 June 2017 - 01:16 AM

Adding to the above question,

 

a document "Sensor Size and Field of View of the Primo 70 Series of Lenses" in the following link says,

 

http://panalab.panav...tags_tid[0]=228

 

Sensor size has no effect on the depth of field. A 21mm at T2.8 will always be a 21mm at T2.8, whether it’s on a 70mm camera, a Red Dragon, or a Super 35 camera. However a 27 mm on a Red Dragon will give you the same Field of View as a 21 mm on Super 35, and using a longer lens gives you less depth of field.

So at the same camera position and with the same framing, a filmmaker will get less depth of field on a Red Dragon than on Super35, but only because he has to use a longer lens.

 

 

Please provide your views.


Edited by Mathew Collins, 18 June 2017 - 01:27 AM.

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#3 Dan Hasson

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Posted 18 June 2017 - 03:37 AM

While sensor size/film gauge affects your DoF, there are of course other factors to what affects it - distance from the subject, t or f stop, focal length, light & composition. But then your t or f stop is affected by you cameras/film ISO.

 

But the wikipedia page can help explain it a lot about DoF for you: https://en.wikipedia.../Depth_of_field


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#4 Mathew Collins

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Posted 18 June 2017 - 06:41 AM

While sensor size/film gauge affects your DoF, there are of course other factors to what affects it - distance from the subject, t or f stop, focal length, light & composition. But then your t or f stop is affected by you cameras/film ISO.

 

But the wikipedia page can help explain it a lot about DoF for you: https://en.wikipedia.../Depth_of_field

 

Thank you Dan.

 

I am aware of the factors distance from the subject, t or f stop, focal length, light & composition.


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#5 Robin R Probyn

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Posted 18 June 2017 - 06:44 AM

Man.. that dedo video is one of the weirdest Ive ever seen.. that voice !!.. and all the rubbish info.. ? its like a piss take xmas video.. 


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#6 David Mullen ASC

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Posted 18 June 2017 - 09:00 AM

Not just focal length, f-stop and distance focused affect depth of field, but also the Circle of Confusion figure used. A 25mm at f/2.8 focused at 5 feet, let's say, has a different depth of field on a smaller format because if shown on the same sized screen as a larger format, the image is being enlarged more so you have to use a more critical Circle of Confusion figure.

However in general larger formats have less depth of field when you match field of view, f-stop, distance focused to a smaller format because you have to use a longer focal length on the larger format to achieve the same field of view as the smaller format.
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#7 Mathew Collins

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Posted 18 June 2017 - 10:10 PM

Not just focal length, f-stop and distance focused affect depth of field, but also the Circle of Confusion figure used. A 25mm at f/2.8 focused at 5 feet, let's say, has a different depth of field on a smaller format because if shown on the same sized screen as a larger format, the image is being enlarged more so you have to use a more critical Circle of Confusion figure.

However in general larger formats have less depth of field when you match field of view, f-stop, distance focused to a smaller format because you have to use a longer focal length on the larger format to achieve the same field of view as the smaller format.

 

 

> A 25mm at f/2.8 focused at 5 feet, let's say, has a different depth of field on a smaller format because if shown on the same sized screen as a larger format, the image is being enlarged more so you have to use a more critical Circle of Confusion figure.

 

Not able to understand the this part.


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#8 Mark Kenfield

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Posted 18 June 2017 - 11:21 PM

Imagine that you're framing up the EXACT same image with two separate formats, the first version is with a 50mm on a S35mm sensor at T/2.8, and the second is with a 25mm on a S16mm sensor at T/2.8.

 

The composition of your images is identical, but the S16mm image has a deeper depth of field because (in order to achieve the equivalent field of view) you're using a wider lens.


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#9 Gregg MacPherson

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Posted 18 June 2017 - 11:44 PM

Mathew,  I think getting a feeling for the field of view relative to the frame size is the key to being intuitively comfortable with this issue.

EDIT: I was was going to quote David to pose that.....


Edited by Gregg MacPherson, 18 June 2017 - 11:47 PM.

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#10 Mathew Collins

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Posted 19 June 2017 - 09:43 PM

Imagine that you're framing up the EXACT same image with two separate formats, the first version is with a 50mm on a S35mm sensor at T/2.8, and the second is with a 25mm on a S16mm sensor at T/2.8.

 

The composition of your images is identical, but the S16mm image has a deeper depth of field because (in order to achieve the equivalent field of view) you're using a wider lens.

 

 

Thank you Mark.

 

What is the meaning of "so you have to use a more critical Circle of Confusion figure"?


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#11 David Mullen ASC

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Posted 20 June 2017 - 04:38 AM

https://en.m.wikiped...le_of_confusion
https://www.cookeopt...s June 2006.pdf
https://books.google...or 16mm&f=false
http://www.dofmaster...matography.html
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#12 Mathew Collins

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Posted 20 June 2017 - 04:44 AM

 

Thank you David.

 

My question is not 'What is circle of confusion?' but 'more critical Circle of Confusion figure'


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#13 Mark Dunn

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Posted 20 June 2017 - 05:08 AM

 

Thank you David.

 

My question is not 'What is circle of confusion?' but 'more critical Circle of Confusion figure'

 

"Critical" is a common English word.

Here it means smaller.


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#14 Robin R Probyn

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Posted 20 June 2017 - 08:51 AM

When my wife uses it.. it means small and alot more.. 


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#15 Mathew Collins

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Posted 20 June 2017 - 09:12 AM

 

"Critical" is a common English word.

Here it means smaller.

 

Does that mean 'small Circle of Confusion figure'?

 

But my understanding was 'critical=urgent'.


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#16 Brian Drysdale

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Posted 20 June 2017 - 09:32 AM

Here are the meanings of "Critical"
 

1.saying that someone or something is bad or wrong:

2.of the greatest importance to the way things might happen:

3.giving opinions or judgments on books, plays, films, etc.:

4.extremely serious or dangerous:

 

In this case I suspect, the meaning is the the second, in referring to the image in the smaller format appearing sharp requires the use of a smaller tcircle of confusion because of the greater magnification..


Edited by Brian Drysdale, 20 June 2017 - 09:34 AM.

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#17 David Mullen ASC

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Posted 20 June 2017 - 01:24 PM

Yes.
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