> Hi everyone,
>
> I am currently using POV-Ray to generate virtual scenes, next I've got to
> analyse these generated images for a specific study. I have to simulate the
> behavior of the default setting of the Go Pro 2 HD.
>
> The default setting of the Go Pro 2 HD :
> ----------------------------------------
>
> Fixed-focal lens : 0.6m to infinity
> Aperture : f/2.8
> HFOV : 170deg
> reso : 1920x1080
>
> I changed the camera setting accordingly :
>
> camera {
>    perspective
>    //spherical
>    location camera_location
>    look_at <0,8.25,0>
>    //right       1.777777778*x
>    right x*image_width/image_height
>    //rotate <0,clock*360,0>
>    //angle hfov
>    //angle 170 43.59
>    //aperture 2.8
>    focal_point <0,6.0,0> //go pro fixed focal -> 0.6m to infinity
>    aperture 0.3571 // go pro aperture : f/2.8
>    blur_samples 20
> }
>
> But everything is blurred from the focal point to infinity, I wanted the inverse
> behavior, however I don't understand how to manage that with the POV-Ray syntax.
>
> Besides, when I set the horizontal FOV (angle) to 170deg, the image is deformed
> and objects look very far.
>
> Does any of you have already tried to simulate the behavior of a real camera and
> could help me fix my little problem ?
>
> Thanks a lot !
>
> Alef,
>
>
>
>

The focal_point define a plane of maximum sharpness. That point IS NOT 
defined relative to the camera but relative to the global coordinate 
system. In your case, it define a plane passing by the point <0, 6, 0> 
and perpendicular to the axis going from the camera location and the 
point_at location. In fact, the focal_point don't even need to be 
located within the visible part of the scene.

You can make it relative to the camera as follow (minimal case):
#declare My_Camera = camera{location 0 look_at z focal_point<0,0,0.8> 
blur_samples 7 aperture 0.3571}
Use a low blur_samples during testing (it will get grany), then set it 
higher for the final render to get a smooth result.

This define a camera siting at the origin, looking toward +Z, using 
focal blur with a focal point situated 0.6 unit in front of it.
If in your scene 1 unit = 10 cm, change 0.6 to 6, or to 60 if you use 1 
unit = 1 cm.

You can now rotate and translate that camera as needed using:
camera{My_Camera rotate Rotation location Cam_location}
or
camera{My_Camera location Cam_location look_at Target_point}

You can set aperture in the declaration or when using the declared camera.
Adjust aperture untill you get the zone of sharpness you want.

I've set the focal plane slightly farther than what you set as the zone 
of sharpness start slightly before the focal plane in the same way it 
does for a real objective.

angle set the angle between the axis of the camera (the center point of 
the image) and the rightmost point of the image. If your angle define 
the angle between the left and right edges, you need to divide it by 2.

need to set: angle 85


The default prespective camera is an ideal pin hole camera. Any straight 
line always remain traight.

Spherical and ultrawhide_angle will display some "barelling", a 
distortion common to uncorrected objectives, especialy of the whide 
angle variety.

For the spherical, you need to explicitely set
angle Horizontal_angle , Vertical_angle.

If you've done already, I highly recomend that you use the version 3.7 
RC7 available from the "Beta" page. It's very stable and is more 
performant. It will use all your cores on a multi-core computer and the 
code for focal blur is much more effecient than before.




Alain

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