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Depth of field of extension tube vs dedicated macro

Started 7 months ago | Questions
erotavlas Regular Member • Posts: 274
Depth of field of extension tube vs dedicated macro

I just got a set  of extension tubes and tried it out on a 70-300 telephoto lens (sony 70-300 FE)  and it definitely helps increase the magnification as I can get closer to subject.  But I noticed I have to decrease the aperture quite a bit (like maybe to F11 - F16) in order to get more of the subject in focus.

Is this the same even for a dedicated macro lens?

Does DOF get any better with wider lenses + extension tube (50mm or wider)?  Or is it strictly a result of the distance to the subject?

 erotavlas's gear list:erotavlas's gear list
Sony a6500 Sony Carl Zeiss Sonnar T* E 24mm F1.8 ZA Carl Zeiss Touit 2.8/12 Sony FE 70-300mm F4.5-5.6 G OSS +2 more
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Joseph S Wisniewski Forum Pro • Posts: 35,461
DOF is controlled by magnification and aperture
1

erotavlas wrote:

I just got a set of extension tubes and tried it out on a 70-300 telephoto lens (sony 70-300 FE) and it definitely helps increase the magnification as I can get closer to subject. But I noticed I have to decrease the aperture quite a bit (like maybe to F11 - F16) in order to get more of the subject in focus.

Yep. What's even worse is that the extension tubes reduce the effective aperture of the lens so that it's even smaller than f/11-f/16, so you get even more diffraction killing the sharpness of the in-focus parts of the image.

Is this the same even for a dedicated macro lens?

Yes. You cannot deny physics.

Does DOF get any better with wider lenses + extension tube (50mm or wider)? Or is it strictly a result of the distance to the subject?

It's strictly a result of magnification. No matter what focal length you use, if you extend it enough to get X magnification, you will have Y depth of field.

There's a technique called "focus stacking" you might want to research.

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Stanley Joseph Wisniewski 1932-2019.
Dad, so much of you is in me.
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Christine Fleischer 1947-2014.
My soulmate. There are no other words.
-----
Rahon Klavanian 1912-2008.
Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.
----
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 Joseph S Wisniewski's gear list:Joseph S Wisniewski's gear list
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AeroPhotographer Regular Member • Posts: 462
Re: Depth of field of extension tube vs dedicated macro
1

Yes, DOF depends solely on magnification, no matter how that magnification is achieved.  See:

https://www.dpreview.com/forums/thread/4624325 Depth of Field

Alan

OP erotavlas Regular Member • Posts: 274
Re: Depth of field of extension tube vs dedicated macro

AeroPhotographer wrote:

Yes, DOF depends solely on magnification, no matter how that magnification is achieved. See:

https://www.dpreview.com/forums/thread/4624325 Depth of Field

Alan

Thanks, I suppose a longer focal length will also help move you further away from subject and increase the depth of field?

 erotavlas's gear list:erotavlas's gear list
Sony a6500 Sony Carl Zeiss Sonnar T* E 24mm F1.8 ZA Carl Zeiss Touit 2.8/12 Sony FE 70-300mm F4.5-5.6 G OSS +2 more
Joseph S Wisniewski Forum Pro • Posts: 35,461
Yes, and no

erotavlas wrote:

AeroPhotographer wrote:

Yes, DOF depends solely on magnification, no matter how that magnification is achieved. See:

https://www.dpreview.com/forums/thread/4624325 Depth of Field

Alan

Thanks, I suppose a longer focal length will also help move you further away from subject

Absolutely.

and increase the depth of field?

No. Literally the only thing that controls DOF is magnification.

-- hide signature --

The term "mirrorless" is totally obsolete. It's time we call out EVIL for what it is. (Or, if you can't handle "Electronic Viewfinder Interchangeable Lens" then Frenchify it and call it "LIVE" for "Lens Interchangeable, Viewfinder Electronic" or "Viseur électronique").
-----
Stanley Joseph Wisniewski 1932-2019.
Dad, so much of you is in me.
-----
Christine Fleischer 1947-2014.
My soulmate. There are no other words.
-----
Rahon Klavanian 1912-2008.
Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.
----
Ciao! Joseph
www.swissarmyfork.com

 Joseph S Wisniewski's gear list:Joseph S Wisniewski's gear list
Nikon D90 Nikon D2X Nikon D3 Nikon D100 Nikon Z7 +48 more
JamesMorgan Junior Member • Posts: 36
Re: Yes, and no

I recently bought a close up filter to use with my Oly 75-300 so am also experimenting with DoF with close up photography.  No doubt it is challenging and with DoF of around 1mm, I am often using focus bracketing in an attempt to find one photograph correctly focused.

As others have pointed out DoF is a function of the magnification of the image - it doesn't matter how you get there, whether with a macro lens, an extender, a close-up filter, a telephoto lens etc.

However, my understanding of post-processing cropping is that whilst this does reduce DoF, it does so in a linear manner rather than according to a square rule if increasing lens focal length.  So, for example, if I increase focal length from 150mm to 300mm, DoF reduces to a quarter, however, if I crop the 150mm image to achieve the same field of view DoF only reduces by around a half.   This can be useful to extract the maximum possible DoF if you don't mind losing a few pixels.

Joseph S Wisniewski Forum Pro • Posts: 35,461
Cropping and enlarging alters f stop...
1

JamesMorgan wrote:

However, my understanding of post-processing cropping is that whilst this does reduce DoF, it does so in a linear manner rather than according to a square rule if increasing lens focal length. So, for example, if I increase focal length from 150mm to 300mm, DoF reduces to a quarter, however, if I crop the 150mm image to achieve the same field of view DoF only reduces by around a half. This can be useful to extract the maximum possible DoF if you don't mind losing a few pixels.

What you're seeing is the crop factor affecting effective f stop along with effective focal length. You gain more DOF, but you burn resolution. Open up to get the resolution back, and you've lost the DOF advantage.

-- hide signature --

The term "mirrorless" is totally obsolete. It's time we call out EVIL for what it is. (Or, if you can't handle "Electronic Viewfinder Interchangeable Lens" then Frenchify it and call it "LIVE" for "Lens Interchangeable, Viewfinder Electronic" or "Viseur électronique").
-----
Stanley Joseph Wisniewski 1932-2019.
Dad, so much of you is in me.
-----
Christine Fleischer 1947-2014.
My soulmate. There are no other words.
-----
Rahon Klavanian 1912-2008.
Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.
----
Ciao! Joseph
www.swissarmyfork.com

 Joseph S Wisniewski's gear list:Joseph S Wisniewski's gear list
Nikon D90 Nikon D2X Nikon D3 Nikon D100 Nikon Z7 +48 more
JamesMorgan Junior Member • Posts: 36
Re: Cropping and enlarging alters f stop...
1

Joseph S Wisniewski wrote:

JamesMorgan wrote:

However, my understanding of post-processing cropping is that whilst this does reduce DoF, it does so in a linear manner rather than according to a square rule if increasing lens focal length. So, for example, if I increase focal length from 150mm to 300mm, DoF reduces to a quarter, however, if I crop the 150mm image to achieve the same field of view DoF only reduces by around a half. This can be useful to extract the maximum possible DoF if you don't mind losing a few pixels.

What you're seeing is the crop factor affecting effective f stop along with effective focal length. You gain more DOF, but you burn resolution. Open up to get the resolution back, and you've lost the DOF advantage.

Agreed.  It does depend on what you final use is for the image as to whether this will be an issue.  If I crop a 20MP image to change FoV from 150mm to 300mm I will end up with a 5MP image.  This would be fine for viewing on an HD monitor or printing up to 8-10 inches.  If I want greater resolution than that, then cropping is not a viable option.

If should also be remembered that DoF is not fixed and depends on how the viewer views the final image.  Most calculators assume viewing the image as a 10x8 photograph viewed from 10 inches.  If I need to view a larger image than that, then the DoF will be smaller than indicated by the calculator.  This is all goverened by the Circle of Confusion.

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