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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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#18 Mathew Collins

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Posted 25 June 2017 - 10:25 PM

Thank you David and Brian. I am trying to understand it.


Edited by Mathew Collins, 25 June 2017 - 10:26 PM.

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#19 Adam Frisch FSF

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Posted 25 June 2017 - 11:12 PM

Depth of field remains the same regardless of focal length as long as the aperture and image size stay the same. Longer lenses do not shorten it, it just appears so because the background gets more magnified.


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#20 Kyryll Sobolev

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Posted 26 June 2017 - 06:36 PM

matthew think of it this way.

theoretically (for lack of better term) sensor size has no effect on dof

practically, however, it very much does

 

say you have a lens on a 16mm camera

then mount that lens to a 8x10 camera, or project it onto a 111'x32' plane

what happens to dof in those cases? nothing happens. it remains the same

 

but, practically speaking, there is no sense using a 16mm lens on larger formats, you will just get vignetting.

so you use a longer lens, or one that covers the larger format, and as a result, you end up with less dof.


Edited by Kyryll Sobolev, 26 June 2017 - 06:36 PM.

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