Override subj. dist. to infinity = hyperfocal point - General Help and Assistance on using CHDK stable releases - CHDK Forum

Override subj. dist. to infinity = hyperfocal point

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shinnen

• 159
Override subj. dist. to infinity = hyperfocal point
« on: 09 / June / 2021, 18:41:59 »
Is setting the 'override subj. dist.' to infinity the same thing as setting the hyperfocal point?
Thanks,
.... john

waterwingz

• 12084
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #1 on: 09 / June / 2021, 23:01:56 »
Is setting the 'override subj. dist.' to infinity the same thing as setting the hyperfocal point?
It shouldn't be.  Infinity is .. well .. infinity.  And the hyperfocal point, IIRC, is a focus distance where everything is in focus from 1/2 that distance out to infinity.
Ported :   A1200    SD940   G10    Powershot N    G16

pigeonhill

• 790
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #2 on: 10 / June / 2021, 03:38:46 »
@shinnen

You may get a little more insight if you look at my Landscape Bracketing Script.

As @waterwingz says, the hyperfocal is the hyperfocal. That is, once you have selected an aperture etc, the hyperfocal doesn’t change with focus.

What does change with focus is the defocus blur at infinity.

At the hyperfocal, this is the defined circle of confusion. At, say, 3 times the hyperfocal distance the infinity blur will be a third of that at the hyperfocal. Of course, when focused at infinity, the infinity defocus blur is ‘zero’.  But note, the overall blur is not zero, ie you always have diffraction blur, which you can estimate from 4N/3, where N is the aperture number. Thus if focused at infinity and, say, at f/9, the blur would be about 12 microns.
« Last Edit: 10 / June / 2021, 07:15:59 by pigeonhill »

shinnen

• 159
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #3 on: 10 / June / 2021, 10:07:04 »
Hi,
Alright. Thanks for setting me straight.
So, by calculating the hyperfocal point, from the tables at dofmaster, here ..... https://www.dofmaster.com/dofjs.html
(using f3.5 and focal length of 4.5mm) I come up with 3.86 feet. Is there a place in CHDK that I can enter this number?
Thanks,
...... john

pigeonhill

• 790
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #4 on: 10 / June / 2021, 10:21:46 »

shinnen

• 159
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #5 on: 10 / June / 2021, 11:16:08 »
....... john

waterwingz

• 12084
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #6 on: 10 / June / 2021, 19:07:17 »
Is there a place in CHDK that I can enter this number?
You can display the hyperfocal distance that CHDK calculates for you with the DOF Calculator.

Or you can use Override Subject Distance to set the MF distance to the hyperfocal distance that CHDK calculates.

But AFAIK you really can't use an externally calculated value unless you write a small script to read that value in and the set the focus manually.
Ported :   A1200    SD940   G10    Powershot N    G16

pigeonhill

• 790
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #7 on: 11 / June / 2021, 00:52:37 »
@shinnen

As @waterwingz suggests, a script will allow you to position focus at the hyperfocal.

However, if you are using the hyperfocal to focus, positioning focus at the CHDK defined hyperfocal will result in an image where the infinity focus is ‘just’ ok, ie based on the ‘usually accepted’ full frame CoC scaled by the camera’s crop factor.

The power of hyperfocal focusing is being able to dial in the required infinity defocus blur you need for your particular case.

Using the standard infinity blur, at a CoC/crop, will be absolutely ok for social media presentation, but may not be ok for a print.

My Landscape Bracketing Script allows you to focus at the required infinity blur and provides that feedback to you. See https://chdk.fandom.com/wiki/Landscape_Focus_Bracketing_:_perfect_near_to_far_focus_brackets

Bottom line: rather than focus at a fixed hyperfocal, I would suggest you look at focusing at a particular infinity blur, ie a multiple of the hyperfocal, plus focus bracketing to recover foreground focus.
« Last Edit: 11 / June / 2021, 01:47:41 by pigeonhill »

shinnen

• 159
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #8 on: 11 / June / 2021, 10:32:13 »
Is there a place in CHDK that I can enter this number?
You can display the hyperfocal distance that CHDK calculates for you with the DOF Calculator.

Or you can use Override Subject Distance to set the MF distance to the hyperfocal distance that CHDK calculates.

But AFAIK you really can't use an externally calculated value unless you write a small script to read that value in and the set the focus manually.
OK. CHDK says that my hyperfocal distance is 1.13 metres (very close to what the online calculator gives as 1.18); so I entered 11,300 as the "Override Subject Distance". Then I did some comparison shots with CHDK activated, and not activated, and the pictures look pretty much the same wrt DOF. Have I done this right.
...... john
« Last Edit: 11 / June / 2021, 10:34:55 by shinnen »

shinnen

• 159
Re: Override subj. dist. to infinity = hyperfocal point
« Reply #9 on: 11 / June / 2021, 10:37:42 »
Oops! I miscalculated. The number should have been 1,130. :'(
..... john