Sensor/ Film size and depth of field

[Mathew Collins]

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 June 18, 2017 by Mathew Collins

[Mathew Collins]

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.panavision.com/panalab-reference-library?page=4&title=&field_document_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 June 18, 2017 by Mathew Collins

[Dan Hasson]

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.org/wiki/Depth_of_field

[Mathew Collins]

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.org/wiki/Depth_of_field

 

Thank you Dan.

 

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

[Robin R Probyn]

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..

[David Mullen ASC]

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.

[Mathew Collins]

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.

[Mark Kenfield]

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.

[Gregg MacPherson]

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 June 19, 2017 by Gregg MacPherson

[Mathew Collins]

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"?

[David Mullen ASC]

https://en.m.wikipedia.org/wiki/Circle_of_confusion

https://www.cookeoptics.com/techdoc/9D03B7A06B44885385257BB40054DA06/Depth%20of%20Field%20Explained-F&DTimes%20June%202006.pdf

https://books.google.com/books?id=uyMYMbjheqgC&pg=PA275&lpg=PA275&dq=circle+of+confusion+for+16mm&source=bl&ots=UOmOYhYlgo&sig=TMvMf81zGXcRAilywYtB84VKJe4&hl=en&sa=X&ved=0ahUKEwiIoYWjj8zUAhVKcj4KHT4gDX8Q6AEINjAF#v=onepage&q=circle%20of%20confusion%20for%2016mm&f=false

http://www.dofmaster.com/cinematography.html

[Mathew Collins]

https://en.m.wikipedia.org/wiki/Circle_of_confusion

https://www.cookeoptics.com/techdoc/9D03B7A06B44885385257BB40054DA06/Depth%20of%20Field%20Explained-F&DTimes%20June%202006.pdf

https://books.google.com/books?id=uyMYMbjheqgC&pg=PA275&lpg=PA275&dq=circle+of+confusion+for+16mm&source=bl&ots=UOmOYhYlgo&sig=TMvMf81zGXcRAilywYtB84VKJe4&hl=en&sa=X&ved=0ahUKEwiIoYWjj8zUAhVKcj4KHT4gDX8Q6AEINjAF#v=onepage&q=circle%20of%20confusion%20for%2016mm&f=false

http://www.dofmaster.com/cinematography.html

 

Thank you David.

 

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

[Mark Dunn]

 

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.

[Robin R Probyn]

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

[Mathew Collins]

 

"Critical" is a common English word.

Here it means smaller.

 

Does that mean 'small Circle of Confusion figure'?

 

But my understanding was 'critical=urgent'.

[Brian Drysdale]

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 June 20, 2017 by Brian Drysdale

[David Mullen ASC]

Yes.

[Mathew Collins]

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

Edited June 26, 2017 by Mathew Collins

[Adam Frisch FSF]

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.

[Kyryll Sobolev]

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 June 26, 2017 by Kyryll Sobolev

[Mathew Collins]

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.

 

Just comparing this with David Mullen quoted on Jun 18th,

 

"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."

 

Can i put it in this way?

 

If i am planning to project an image which is shot in 16mm onto 70mm format, image being enlarged so we would use use small circle of confusion while shooting in 16mm.

[Brian Drysdale]

The small circle of confusion remains a requirement on 16mm, regardless of going onto a 70mm release. You may even become more demanding, by only selecting the sharpest lenses, if it's being shown on larger screen.

[Kyryll Sobolev]

Can i put it in this way?

 

If i am planning to project an image which is shot in 16mm onto 70mm format, image being enlarged so we would use use small circle of confusion while shooting in 16mm.

 

whatever format you are shooting on, use the known CoC values for that format (or plug in your own ones) to calculate dof while you are on set

 

what happens to the shot material after is a different story - you can project it to youtube or imax screen if you like