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Author Topic: How (and why) does sensor size change DOF?  (Read 26113 times)

ecka

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Re: How (and why) does sensor size change DOF?
« Reply #60 on: July 16, 2013, 09:00:37 AM »
Wow...this became a way bigger discussion than i intented it to be. :o

So if i got everything right it is like that:

Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF. And that makes total sense to me because the lens projects the same image as before but on a smaller area to capture it.

And same focal length + same aperture + same object framing (which means bigger distance to subject on smaller formats) = bigger DoF on small formats because the focal distance is further away and smaller DoF on bigger formats because the focal distance is closer to MFD.

I hope my english is good enouh so everybody undertood what i meant...  :-[

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Re: How (and why) does sensor size change DOF?
« Reply #60 on: July 16, 2013, 09:00:37 AM »

privatebydesign

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Re: How (and why) does sensor size change DOF?
« Reply #61 on: July 16, 2013, 09:42:58 AM »
Wow...this became a way bigger discussion than i intented it to be. :o

So if i got everything right it is like that:

Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF. And that makes total sense to me because the lens projects the same image as before but on a smaller area to capture it.

And same focal length + same aperture + same object framing (which means bigger distance to subject on smaller formats) = bigger DoF on small formats because the focal distance is further away and smaller DoF on bigger formats because the focal distance is closer to MFD.

I hope my english is good enouh so everybody undertood what i meant...  :-[

Greetings from Germany,
Knut Skywalker

Yes, you've got it right.

No, that is not correct.

"Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF."

That scenario, assuming you are comparing same sized reproductions (print or screen), results in less DoF from the crop camera because it is has a smaller CoC. Think of it like this, you have to enlarge the crop cameras image 2.5 times more (by area) than the ff one, bigger reproduction ratio = less dof. Don't forget any detail of the crop camera image is reproduced bigger than the same detail from the ff image on a same sized print (or screen).

IF, using your above scenario, you compared two prints from the different sensors where the details of the subject were the same size, so the crop camera print would be 40% the size of the ff print, then the dof would be identical.

You cannot remove reproduction size from the DoF calculation, DoF calculators assume a base standard, often an 8"x10" print viewed at 12", if you compare two same sized prints from different sized sensors then the smaller sensor has been enlarged more.

This is all covered and explained in my first reply, the second post, on page one. "If pictures are taken from the same distance using the same f-number, same focal length, and the final images are the same size, the smaller format has less DOF."
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Re: How (and why) does sensor size change DOF?
« Reply #62 on: July 16, 2013, 09:49:47 AM »
Wow...this became a way bigger discussion than i intented it to be. :o

So if i got everything right it is like that:

Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF. And that makes total sense to me because the lens projects the same image as before but on a smaller area to capture it.

And same focal length + same aperture + same object framing (which means bigger distance to subject on smaller formats) = bigger DoF on small formats because the focal distance is further away and smaller DoF on bigger formats because the focal distance is closer to MFD.

I hope my english is good enouh so everybody undertood what i meant...  :-[

Greetings from Germany,
Knut Skywalker

Yes, you've got it right.

No, that is not correct.

"Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF."

That scenario, assuming you are comparing same sized reproductions (print or screen), results in less DoF from the crop camera because it is has a smaller CoC. Think of it like this, you have to enlarge the crop cameras image 2.5 times more (by area) than the ff one, bigger reproduction ratio = less dof. Don't forget any detail of the crop camera image is reproduced bigger than the same detail from the ff image on a same sized print (or screen).

IF, using your above scenario, you compared two prints from the different sensors where the details of the subject were the same size, so the crop camera print would be 40% the size of the ff print, then the dof would be identical.

You cannot remove reproduction size from the DoF calculation, DoF calculators assume a base standard, often an 8"x10" print viewed at 12", if you compare two same sized prints from different sized sensors then the smaller sensor has been enlarged more.

This is all covered and explained in my first reply, the second post, on page one. "If pictures are taken from the same distance using the same f-number, same focal length, and the final images are the same size, the smaller format has less DOF."

Quite correct. Canon itself uses a COC 0.035mm in DOF calculations for FF. On APS-C the image must be enlarged more to produce a 7x5 inch print, which means a smaller COC is needed and hence for APS-C, Canon uses a COC of 0.019mm in its calculations.
« Last Edit: July 16, 2013, 09:56:31 AM by J.R. »
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ecka

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Re: How (and why) does sensor size change DOF?
« Reply #63 on: July 16, 2013, 10:08:06 AM »
Wow...this became a way bigger discussion than i intented it to be. :o

So if i got everything right it is like that:

Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF. And that makes total sense to me because the lens projects the same image as before but on a smaller area to capture it.

And same focal length + same aperture + same object framing (which means bigger distance to subject on smaller formats) = bigger DoF on small formats because the focal distance is further away and smaller DoF on bigger formats because the focal distance is closer to MFD.

I hope my english is good enouh so everybody undertood what i meant...  :-[

Greetings from Germany,
Knut Skywalker

Yes, you've got it right.

No, that is not correct.

"Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF."

That scenario, assuming you are comparing same sized reproductions (print or screen), results in less DoF from the crop camera because it is has a smaller CoC. Think of it like this, you have to enlarge the crop cameras image 2.5 times more (by area) than the ff one, bigger reproduction ratio = less dof. Don't forget any detail of the crop camera image is reproduced bigger than the same detail from the ff image on a same sized print (or screen).

IF, using your above scenario, you compared two prints from the different sensors where the details of the subject were the same size, so the crop camera print would be 40% the size of the ff print, then the dof would be identical.

You cannot remove reproduction size from the DoF calculation, DoF calculators assume a base standard, often an 8"x10" print viewed at 12", if you compare two same sized prints from different sized sensors then the smaller sensor has been enlarged more.

This is all covered and explained in my first reply, the second post, on page one. "If pictures are taken from the same distance using the same f-number, same focal length, and the final images are the same size, the smaller format has less DOF."

Quite correct. Canon itself uses a COC 0.035mm in DOF calculations for FF. On APS-C the image must be enlarged more to produce a 7x5 inch print, which means a smaller COC is needed and hence for APS-C, Canon uses a COC of 0.019mm in its calculations.

So, in your reality, if you print the same picture in two different sizes, the bigger one will have less DoF? :D
Good lord... I'm wasting my time here  ???
Same logic - there is a magical print size which makes your P&S images look like they were shot using a FF camera? :D ... and the next one is even better?
« Last Edit: July 16, 2013, 10:10:04 AM by ecka »
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Re: How (and why) does sensor size change DOF?
« Reply #64 on: July 16, 2013, 10:18:30 AM »
Wow...this became a way bigger discussion than i intented it to be. :o

So if i got everything right it is like that:

Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF. And that makes total sense to me because the lens projects the same image as before but on a smaller area to capture it.

And same focal length + same aperture + same object framing (which means bigger distance to subject on smaller formats) = bigger DoF on small formats because the focal distance is further away and smaller DoF on bigger formats because the focal distance is closer to MFD.

I hope my english is good enouh so everybody undertood what i meant...  :-[

Greetings from Germany,
Knut Skywalker

Yes, you've got it right.

No, that is not correct.

"Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF."

That scenario, assuming you are comparing same sized reproductions (print or screen), results in less DoF from the crop camera because it is has a smaller CoC. Think of it like this, you have to enlarge the crop cameras image 2.5 times more (by area) than the ff one, bigger reproduction ratio = less dof. Don't forget any detail of the crop camera image is reproduced bigger than the same detail from the ff image on a same sized print (or screen).

IF, using your above scenario, you compared two prints from the different sensors where the details of the subject were the same size, so the crop camera print would be 40% the size of the ff print, then the dof would be identical.

You cannot remove reproduction size from the DoF calculation, DoF calculators assume a base standard, often an 8"x10" print viewed at 12", if you compare two same sized prints from different sized sensors then the smaller sensor has been enlarged more.

This is all covered and explained in my first reply, the second post, on page one. "If pictures are taken from the same distance using the same f-number, same focal length, and the final images are the same size, the smaller format has less DOF."

Quite correct. Canon itself uses a COC 0.035mm in DOF calculations for FF. On APS-C the image must be enlarged more to produce a 7x5 inch print, which means a smaller COC is needed and hence for APS-C, Canon uses a COC of 0.019mm in its calculations.

So, in your reality, if you print the same picture in two different sizes, the bigger one will have less DoF? :D
Good lord... I'm wasting my time here  ???
Same logic - there is a magical print size which makes your P&S images look like they were shot using a FF camera? :D

Yes that is the reality I live in, unbeknown to you it is also the reality you live in, ignorance is bliss, you are wasting everybody's time here.....

Reproduction size and viewing distances are fundamental to DoF calculations, you cannot work out DoF figures without knowing how big your print will be and the viewing distance, as I keep saying, DoF calculators often work to the standard of an 8"x10" print viewed at 12".

Read about CoC, you know that "technical mumbo-jumbo" "you can ignore", well it turns out you can't ignore it if you want to understand the answer to the OP's question.
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ecka

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Re: How (and why) does sensor size change DOF?
« Reply #65 on: July 16, 2013, 10:44:28 AM »
Wow...this became a way bigger discussion than i intented it to be. :o

So if i got everything right it is like that:

Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF. And that makes total sense to me because the lens projects the same image as before but on a smaller area to capture it.

And same focal length + same aperture + same object framing (which means bigger distance to subject on smaller formats) = bigger DoF on small formats because the focal distance is further away and smaller DoF on bigger formats because the focal distance is closer to MFD.

I hope my english is good enouh so everybody undertood what i meant...  :-[

Greetings from Germany,
Knut Skywalker

Yes, you've got it right.

No, that is not correct.

"Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF."

That scenario, assuming you are comparing same sized reproductions (print or screen), results in less DoF from the crop camera because it is has a smaller CoC. Think of it like this, you have to enlarge the crop cameras image 2.5 times more (by area) than the ff one, bigger reproduction ratio = less dof. Don't forget any detail of the crop camera image is reproduced bigger than the same detail from the ff image on a same sized print (or screen).

IF, using your above scenario, you compared two prints from the different sensors where the details of the subject were the same size, so the crop camera print would be 40% the size of the ff print, then the dof would be identical.

You cannot remove reproduction size from the DoF calculation, DoF calculators assume a base standard, often an 8"x10" print viewed at 12", if you compare two same sized prints from different sized sensors then the smaller sensor has been enlarged more.

This is all covered and explained in my first reply, the second post, on page one. "If pictures are taken from the same distance using the same f-number, same focal length, and the final images are the same size, the smaller format has less DOF."

Quite correct. Canon itself uses a COC 0.035mm in DOF calculations for FF. On APS-C the image must be enlarged more to produce a 7x5 inch print, which means a smaller COC is needed and hence for APS-C, Canon uses a COC of 0.019mm in its calculations.

So, in your reality, if you print the same picture in two different sizes, the bigger one will have less DoF? :D
Good lord... I'm wasting my time here  ???
Same logic - there is a magical print size which makes your P&S images look like they were shot using a FF camera? :D

Yes that is the reality I live in, unbeknown to you it is also the reality you live in, ignorance is bliss, you are wasting everybody's time here.....

Reproduction size and viewing distances are fundamental to DoF calculations, you cannot work out DoF figures without knowing how big your print will be and the viewing distance, as I keep saying, DoF calculators often work to the standard of an 8"x10" print viewed at 12".

Read about CoC, you know that "technical mumbo-jumbo" "you can ignore", well it turns out you can't ignore it if you want to understand the answer to the OP's question.

The CoC is not about DoF. When there are 3 parts in the image - sharp (DoF), blur (OOF) and "not sure", the CoC is about the "not sure" part.

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Re: How (and why) does sensor size change DOF?
« Reply #66 on: July 16, 2013, 10:46:19 AM »
Wow...this became a way bigger discussion than i intented it to be. :o

So if i got everything right it is like that:

Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF. And that makes total sense to me because the lens projects the same image as before but on a smaller area to capture it.

And same focal length + same aperture + same object framing (which means bigger distance to subject on smaller formats) = bigger DoF on small formats because the focal distance is further away and smaller DoF on bigger formats because the focal distance is closer to MFD.

I hope my english is good enouh so everybody undertood what i meant...  :-[

Greetings from Germany,
Knut Skywalker

Yes, you've got it right.

No, that is not correct.

"Same focal length + same aperture + same distance to subject on different formats =  different FoV but with same same DoF."

That scenario, assuming you are comparing same sized reproductions (print or screen), results in less DoF from the crop camera because it is has a smaller CoC. Think of it like this, you have to enlarge the crop cameras image 2.5 times more (by area) than the ff one, bigger reproduction ratio = less dof. Don't forget any detail of the crop camera image is reproduced bigger than the same detail from the ff image on a same sized print (or screen).

IF, using your above scenario, you compared two prints from the different sensors where the details of the subject were the same size, so the crop camera print would be 40% the size of the ff print, then the dof would be identical.

You cannot remove reproduction size from the DoF calculation, DoF calculators assume a base standard, often an 8"x10" print viewed at 12", if you compare two same sized prints from different sized sensors then the smaller sensor has been enlarged more.

This is all covered and explained in my first reply, the second post, on page one. "If pictures are taken from the same distance using the same f-number, same focal length, and the final images are the same size, the smaller format has less DOF."

Quite correct. Canon itself uses a COC 0.035mm in DOF calculations for FF. On APS-C the image must be enlarged more to produce a 7x5 inch print, which means a smaller COC is needed and hence for APS-C, Canon uses a COC of 0.019mm in its calculations.

So, in your reality, if you print the same picture in two different sizes, the bigger one will have less DoF? :D
Good lord... I'm wasting my time here  ???
Same logic - there is a magical print size which makes your P&S images look like they were shot using a FF camera? :D ... and the next one is even better?

This reality and comes from Canon directly and if instead of pointless arguing if you undertook a little bit of research, you may learn something. At the cost of wasting my time, I point you to these "official" Canon links -

http://cpn.canon-europe.com/content/education/technical/depth_of_field_calculator.do
http://cpn.canon-europe.com/content/education/infobank/depth_of_field/depth_of_field.do

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Re: How (and why) does sensor size change DOF?
« Reply #66 on: July 16, 2013, 10:46:19 AM »

Etienne

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Re: How (and why) does sensor size change DOF?
« Reply #67 on: July 16, 2013, 11:01:37 AM »
Pointless discussion.

In practice, if you want to achieve the same depth of field on a crop as FF, you need to open the aperture on the crop camera by 1.3 stops.

Now ... let the confusion of circulars begin

insanitybeard

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Re: How (and why) does sensor size change DOF?
« Reply #68 on: July 16, 2013, 11:04:27 AM »
Pointless discussion.

In practice, if you want to achieve the same depth of field on a crop as FF, you need to open the aperture on the crop camera by 1.3 stops.

Now ... let the confusion of circulars begin

How is it a pointless discussion when the original question, explicitly was : 'How (and why) does sensor size change DOF?'
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privatebydesign

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Re: How (and why) does sensor size change DOF?
« Reply #69 on: July 16, 2013, 11:07:00 AM »

The CoC is not about DoF. When there are 3 parts in the image - sharp (DoF), blur (OOF) and "not sure", the CoC is about the "not sure" part.

I am sorry, you are so incorrect about so much in that short statement it is practically impossible to try to start to put you right. Please go and read the two links I posted on page one.

Also this link might help you better appreciate the interconnected and inseparable nature of CoC and DoF. http://en.wikipedia.org/wiki/Hyperfocal_distance
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Etienne

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Re: How (and why) does sensor size change DOF?
« Reply #70 on: July 16, 2013, 11:08:10 AM »
To be even more clear, here is an example calculation taken from http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

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Re: How (and why) does sensor size change DOF?
« Reply #71 on: July 16, 2013, 11:12:29 AM »
In practice, if you want to achieve the same depth of field on a crop as FF, you need to open the aperture on the crop camera by 1.3 stops.

In practice, it helps to give practical advice.   ::)

If I am shooting with my 85L II at f/1.2 on my 1D X, then I mount that lens on my EOS M, please tell me how, in practice, I can achieve the same DoF by opening up the aperture on the crop camera by 1.3 stops?   ::)

I understand what you mean, but it might help to phrase it the opposite way...
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Etienne

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Re: How (and why) does sensor size change DOF?
« Reply #72 on: July 16, 2013, 11:17:26 AM »
In practice, if you want to achieve the same depth of field on a crop as FF, you need to open the aperture on the crop camera by 1.3 stops.

In practice, it helps to give practical advice.   ::)

If I am shooting with my 85L II at f/1.2 on my 1D X, then I mount that lens on my EOS M, please tell me how, in practice, I can achieve the same DoF by opening up the aperture on the crop camera by 1.3 stops?   ::)

I understand what you mean, but it might help to phrase it the opposite way...

Of course you can't open past max aperture. That's why some people buy FF - crop cameras can't get there (super-shallow DOF).

If you prefer: to get the deeper DOF of a crop on a FF camera you need to close the aperture by 1.3 stops on the FF camera.

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Re: How (and why) does sensor size change DOF?
« Reply #72 on: July 16, 2013, 11:17:26 AM »

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Re: How (and why) does sensor size change DOF?
« Reply #73 on: July 16, 2013, 11:27:21 AM »
If you take two pictures at the same position with the same lens on both a crop and a full frame, the distance between the nearest in focus object and the furthest away in focus object will be the same, so the depth of field does not change. Obviously the image captured will be different on each.

However, if you're talking about the depth of field for an equivalent picture, you'd have to move the full frame camera closer which would result in a reduced depth of field.
This is correct.

The optics are identical.

With a cropped-frame camera, you are cropping the frame. It's the equivalent of taking a picture with a full-frame camera, and cropping in Lightroom or Picasa (resolution and image quality aside).

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Re: How (and why) does sensor size change DOF?
« Reply #74 on: July 16, 2013, 04:34:31 PM »
If you take two pictures at the same position with the same lens on both a crop and a full frame, the distance between the nearest in focus object and the furthest away in focus object will be the same, so the depth of field does not change. Obviously the image captured will be different on each.

However, if you're talking about the depth of field for an equivalent picture, you'd have to move the full frame camera closer which would result in a reduced depth of field.
This is correct.

The optics are identical.

With a cropped-frame camera, you are cropping the frame. It's the equivalent of taking a picture with a full-frame camera, and cropping in Lightroom or Picasa (resolution and image quality aside).

DoF does not rely solely on optics, so badgerpiper's  statement is false. DoF relies on apparent aperture (optics) and subject magnification (optics, reproduction size and viewing distance).

If you look at same sized prints, as common sense dictates you must, the crop camera capture is enlarged more, so the CoC is smaller, so the DoF is less.

Why doesn't everybody who is inclined to post read the links I have provided? It is all in there. Depending on how you make your comparison, and you have to clearly state the way you want to compare the captures, a smaller sensor can be shown to have more DoF than a ff camera, the same DoF, or as in this instance, less DoF than that ff camera.

You cannot separate DoF from subject magnification and viewing distance at the output size.

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Re: How (and why) does sensor size change DOF?
« Reply #74 on: July 16, 2013, 04:34:31 PM »