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29 Mar 2024 03:21:20 EDT (-0400)
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From: Mike Horvath
Subject: Re: Focal Blur
Date: 9 Nov 2016 16:24:53
Message: <58239425$1@news.povray.org>
On 11/9/2016 12:28 AM, omniverse wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
>> http://wiki.povray.org/content/Reference:Camera#Focal_Blur
>>
>> How can a plane be parallel to the camera? Can't a plane only be
>> perpendicular to a vector?
>>
>> Also, I don't understand why a plane is used at all. All points
>> equidistant from focal_point should form a sphere, don't they?
>
> Probably parallel in the view sense, every plane forward of the camera view
> would be considered parallel.
> Someone else would need to answer that second part, but I think the way it works
> is to simply use a flat plane like orthographic projection does. Maybe... maybe
> not.
>
> I looked at your SDL and the new screen.inc (I renamed mine here screen2.inc to
> not mix it up with the old one).
>
> Found that by using aperture 0.01 to focus the blurring while testing, and using
> the camera location instead of <0,0,0> I could get a look at the text again by
> adding a little z to it.
> Of course, it blurs away immediately after clock increases away from 0.
>
>      focal_point     CameraLocation+z*0.4
>
> If 0.3 or 0.5 is used the text blurs out, so obviously there's a very narrow
> focus area.
> I don't know if you will be able to discover a method to keep the text at the
> focal plane but seems like it shouldn't be impossible either.
>
> Bob
>
>

Eventually I got the text to show up, but as you said it doesn't stay in 
focus as the clock increases. I gave up and added the text using 
ImageMagick instead.

Mike


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From: Mike Horvath
Subject: Re: focal_point
Date: 10 Nov 2016 08:06:36
Message: <582470dc$1@news.povray.org>
Can I simulate an f-number of the camera by using the focal length and 
aperture in a calculation? Is the aperture supposed to be a physical 
measurement? Thanks.


Mike


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From: Mike Horvath
Subject: Re: focal_point
Date: 10 Nov 2016 10:10:51
Message: <58248dfb$1@news.povray.org>
On 11/10/2016 8:06 AM, Mike Horvath wrote:
> Can I simulate an f-number of the camera by using the focal length and
> aperture in a calculation? Is the aperture supposed to be a physical
> measurement? Thanks.
>
>
> Mike

For instance, I have the following numbers:

	#local CameraDistance	= 16;
	#local CameraAperture	= clock * 4;
	#local CameraFStop	= CameraDistance/CameraAperture;

Mike


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From: clipka
Subject: Re: focal_point
Date: 10 Nov 2016 11:50:07
Message: <5824a53f$1@news.povray.org>
Am 10.11.2016 um 14:06 schrieb Mike Horvath:
> Can I simulate an f-number of the camera by using the focal length and
> aperture in a calculation? Is the aperture supposed to be a physical
> measurement? Thanks.

The `aperture` setting is the (virtual) size of the diaphragm opening in
POV-Ray units, though I keep forgetting whether it is the diameter or
the radius.


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From: Mike Horvath
Subject: Re: focal_point
Date: 10 Nov 2016 12:38:03
Message: <5824b07b@news.povray.org>
On 11/10/2016 11:50 AM, clipka wrote:
> Am 10.11.2016 um 14:06 schrieb Mike Horvath:
>> Can I simulate an f-number of the camera by using the focal length and
>> aperture in a calculation? Is the aperture supposed to be a physical
>> measurement? Thanks.
>
> The `aperture` setting is the (virtual) size of the diaphragm opening in
> POV-Ray units, though I keep forgetting whether it is the diameter or
> the radius.
>

Thank you. Could you check whether it is the diameter or radius in the 
code? It is commonly supposed to be diameter according to Wikipedia.

Mike


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From: Cousin Ricky
Subject: Re: focal_point
Date: 10 Nov 2016 19:00:59
Message: <58250a3b$1@news.povray.org>
On 2016-11-10 12:50 PM (-4), clipka wrote:
> The `aperture` setting is the (virtual) size of the diaphragm opening in
> POV-Ray units, though I keep forgetting whether it is the diameter or
> the radius.

In my experience, it's neither.  Comparing aperture to a jittered 
camera, it seems that dividing the aperture by about 2.7 or so yields 
the diameter.  (Or is it multiplying by 2.7...?)


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From: clipka
Subject: Re: focal_point
Date: 10 Nov 2016 22:21:44
Message: <58253948$1@news.povray.org>
Am 10.11.2016 um 18:38 schrieb Mike Horvath:
> On 11/10/2016 11:50 AM, clipka wrote:
>> Am 10.11.2016 um 14:06 schrieb Mike Horvath:
>>> Can I simulate an f-number of the camera by using the focal length and
>>> aperture in a calculation? Is the aperture supposed to be a physical
>>> measurement? Thanks.
>>
>> The `aperture` setting is the (virtual) size of the diaphragm opening in
>> POV-Ray units, though I keep forgetting whether it is the diameter or
>> the radius.
>>
> 
> Thank you. Could you check whether it is the diameter or radius in the
> code? It is commonly supposed to be diameter according to Wikipedia.

There's a line

    r = camera.Aperture * 0.5

in the source code, indicating that the `aperture` parameter is intended
to specify the diameter.

But maybe someone can check Cousin Ricky's claim that the size is off by
a factor.


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