Circle of Cunfusion on DOF Calculator - General Help and Assistance on using CHDK stable releases - CHDK Forum
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# Circle of Cunfusion on DOF Calculator

• 3 Replies
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#### ristow

• 6
##### Circle of Cunfusion on DOF Calculator
« on: 29 / March / 2011, 14:15:55 »
Hi, people!!

I was reading some articles about DOF, hyperfocal distance, etc, and now I'm wondering if the DOF Calculator of CHDK uses the camera specified circle of confusion value.

According to the site below, the hyperfocal distance formula uses the circle of confusion value, and the Near and Far Limits are derived from the hyperfocal distance.

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

In the same website, there's a list of many cameras' circle of confusion value. They differ a lot, for example, between EOS 1D and PS A95.

Does anyone knows if the DOF Calculator uses the specified circle of confusion?

Thanks a lot!

See ya!

#### Microfunguy

• 4037
##### Re: Circle of Cunfusion on DOF Calculator
« Reply #1 on: 29 / March / 2011, 14:24:42 »
Does anyone knows if the DOF Calculator uses the specified circle of confusion?

If you look at the source code for various cameras, you can see the value (in microns) that CHDK uses.

For example, for the S95 at the bottom of this page http://tools.assembla.com/chdk/browser/trunk/platform/s95/shooting.c the COF is seven microns.

That is 0.007 mm.

COF is not an absolute, scientific value .. it is based on assumptions about the observer.

David

#### ristow

• 6
##### Re: Circle of Cunfusion on DOF Calculator
« Reply #2 on: 29 / March / 2011, 14:28:01 »
Thanks a lot, David!

#### foton

• 14
##### Re: Circle of Cunfusion on DOF Calculator
« Reply #3 on: 14 / April / 2012, 10:02:07 »
If somebody want to have the same blur from CoF as from DLA (Diffraction limited aperture) as used on the-digital-picture.com, he should use abut 3 times lower numbers than these used by chdk or dofmaster. As an alternative he can increase hyperfocal distance calculated by chdk 3 times.

Effect of blur from DLA (blured after moving mouse on image): http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=739&Camera=453&Sample=0&FLI=0&API=3&LensComp=739&CameraComp=453&SampleComp=0&FLIComp=0&APIComp=5 . Default values from CHDK and DOFMaster will create about 3 times more blur on distant subjects.
« Last Edit: 15 / April / 2012, 18:15:43 by foton »