Am 19.06.2018 um 09:14 schrieb CrisDamian:
> Alain <kua### [at] videotronca> wrote:
>> In POV-Ray, there is no real diameter for the camera and no real focal
>> length. Unless defined otherwise, it's an ideal pinhole camera.
>>
>> When you want to enable focal blur, you need to define an arbitrary
>> aperture and set a focal point. The effective focal plane is
>> perpendicular to the line going from the camera to the focal point.
>> There is no concept of f stops.
>>
>> The area of sharpness depend on the ratio between the aperture and the
>> distance from the camera location to the focal point
>>
>> Sample camera with focal blur :
>>
>> camera{location -20*z
>>   up y // default
>>   direction z // default
>>   right 4/3*x // default if version <= 3.7
>>   aperture 0.25
>>   focal_point <0,0,0> // default
>>   blur_samples 100// maximum number of samples to take.
>>   confidence 0.99 //Must be less than 1
>>   variance 1/256 //must NOT be zero
>> }
>>
>> This setup result in a camera that is close to a camera at f80 with an
>> horizontal field of view of about 40°.
>> The samples are taken in a roughly circular pattern.
>> You can set a minimum number of samples by using two values for
>> blur_samples :
>> blur_samples 12, 100
>> The samples are simply averaged to get the final value for the current
>> pixel been rendered.
> 
> I have found an attached `patio_stereo_near2.pov` file with something like this:
> 
>     camera{
>       location cam_pos+half_interocular*dir_right*(clock*2-1)
>       direction
> cam_dir-vlength(cam_dir)*dir_right*half_interocular/convergence_dist*(clock*2-1)
>       up        cam_up
>       right     cam_right
>       focal_point fountain_pos
>       aperture 10     // twice much blurring
>       blur_samples 800      // many samples, high quality image
>       variance 0. // 0001 // see pov-ray soc on focal blur
>     }
> 
> So it means that the focal plane is perpendicular to `direction` and goes
> through `focal_point`.
> My goal is to find the diameter of the point spread function (also called the
> circle of confusion https://en.wikipedia.org/wiki/Circle_of_confusion) with
> respect to depth.

Near the image center, POV-Ray's focal blur model approaches that of an
idealized thin lens, with an idealized aperture placed right in the lens
plane:

The `location` vector specifies the center of the lens within the scene,
in scene units.

The `direction` vector specifies the direction of the optical axis. Its
length is only relevant with respect to the `up` and `right` vectors,
and only if no `angle` parameter is specified.

The `up` and `right` vectors specify the orientation of the camera
sensor; the ratio of their lengths also specifies the "physical" aspect
ratio.

In the absence of an `angle` parameter, the ratio between the lengths of
the `direction` and `right` vectors also governs the horizontal angle of
view. Presuming orthogonal vectors, the angle is
alpha=2*atan(|right|/|direction|).

The `focal_point` vector's length, in scene units, specifies the
distance along the optical axis at which an object would be in full
focus; the vector's direction is actually ignored.

The `aperture` setting specifies the size of the camera aperture in
scene units.


Further from the image center, POV-Ray's focal blur model becomes
increasingly non-realistic: Rather than a plane of focus, POV-Ray's
focal blur model actually has a sphere of focus, and the aperture is
also modeled to have spherical symmetry.

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