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by Mark L on Sun Mar 08, 2020 2:40 pm
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What is an appropriate value to use for the circle of confusion with a Sony a7R IV?

I am just starting to learn about this and am not sure how sensor density/resolution impacts it.  Is the circle of confusion different for the a7R II versus the a7R IV?

Thanks for any and all help,
Mark
 

by E.J. Peiker on Sun Mar 08, 2020 5:17 pm
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If you want to be super strict, use 0.10. You will probably be OK around 0.13 microns.
 

by Mark L on Sun Mar 08, 2020 5:21 pm
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Thank you!
 

by Andrew_5488 on Mon Mar 09, 2020 9:33 am
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E.J. Peiker wrote:If you want to be super strict, use 0.10.  You will probably be OK around 0.13 microns.

Can you expand ?
Photopills is using value of 0.03mm which is 30 microns for CoC for Sony a7r4.

Thanks
 

by E.J. Peiker on Mon Mar 09, 2020 10:47 am
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Andrew_5488 wrote:
E.J. Peiker wrote:If you want to be super strict, use 0.10.  You will probably be OK around 0.13 microns.

Can you expand ?
Photopills is using value of 0.03mm which is 30 microns for CoC for Sony a7r4.

Thanks
That is the old default from the film days and is absolutely inappropriate for modern high resolution sensors.  I wouldn't use that value on a 24 megapixel camera much less a 61mp one.

I did make a mistake above though, I meant to say 10 microns or 0.01 or 13 microns or 0.013.
 

by E.J. Peiker on Mon Mar 09, 2020 10:52 am
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Andrew_5488 wrote:
E.J. Peiker wrote:If you want to be super strict, use 0.10.  You will probably be OK around 0.13 microns.

Can you expand ?
Photopills is using value of 0.03mm which is 30 microns for CoC for Sony a7r4.

Thanks
That is the old default from the film days and is absolutely inappropriate for modern high resolution sensors.  I wouldn't use that value on a 24 megapixel camera much less a 61mp one.  If you want the resolution of approximately a 12 megapixel camera at the closest and farthest "in-focus" point then use 0.030 or 0.029 but if you actually want to record the full resolution of the sensor, you will need a much smaller value.  The problem is that if you do that, it will force you to use a smaller aperture which then results in diffraction so you are painted into an ever decreasing box.  This is why so many of us use focus stacking as a matter of routine in landscape photography now as it allows us to use non-diffraction apertures and expand the DOF as close and far as we need.

I did make a mistake above though, I meant to say 10 microns or 0.01 or 13 microns or 0.013.
 

by signgrap on Mon Mar 09, 2020 12:26 pm
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E.J., On a Sony a7R IV what is smallest apperture before Diffraction Limited Aperture?
I've been using f/6.7 but was wondering if it was safe to go somewhat smaller?
Dick Ludwig
 

by E.J. Peiker on Mon Mar 09, 2020 1:35 pm
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signgrap wrote:E.J., On a Sony a7R IV what is smallest apperture before Diffraction Limited Aperture?
I've been using f/6.7 but was wondering if it was safe to go somewhat smaller?
Yes, technically it's f/6.7 but you will likely not see anything with the human eye until about f/9 at the earliest.  If you are using Capture one, use the diffraction correction option under the Lens tab to initiate deconvolution sharpening designed to counter diffraction and that should get you at least to f/13 before any serious effects, beyond f/16 you are definitely going to lose quite a bit of resolution.
 

by signgrap on Mon Mar 09, 2020 6:54 pm
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E.J. Peiker wrote:
signgrap wrote:E.J., On a Sony a7R IV what is smallest apperture before Diffraction Limited Aperture?
I've been using f/6.7 but was wondering if it was safe to go somewhat smaller?
Yes, technically it's f/6.7 but you will likely not see anything with the human eye until about f/9 at the earliest.  If you are using Capture one, use the diffraction correction option under the Lens tab to initiate deconvolution sharpening designed to counter diffraction and that should get you at least to f/13 before any serious effects, beyond f/16 you are definitely going to lose quite a bit of resolution.
What aperture would you use for focus stacking?
Dick Ludwig
 

by E.J. Peiker on Tue Mar 10, 2020 2:14 am
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signgrap wrote:
E.J. Peiker wrote:
signgrap wrote:E.J., On a Sony a7R IV what is smallest apperture before Diffraction Limited Aperture?
I've been using f/6.7 but was wondering if it was safe to go somewhat smaller?
Yes, technically it's f/6.7 but you will likely not see anything with the human eye until about f/9 at the earliest.  If you are using Capture one, use the diffraction correction option under the Lens tab to initiate deconvolution sharpening designed to counter diffraction and that should get you at least to f/13 before any serious effects, beyond f/16 you are definitely going to lose quite a bit of resolution.
What aperture would you use for focus stacking?
f/5.6 to f/8 is fine.
 

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