well,I'd like to put forward a question,"How to Calculate or know the Focal
Length of the perspective type Camera in POV-RAY3.6",can anybody be so kind
to help me? I am a new user to the POV,Thanks!

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Normally, POV-Ray's camera doesn't have any sort of "focus." There is an
optional "focal blur" feature, in which you specify a focal point whose
distance from the camera is then the focal length, but by default, without
this, there is no focal length.

 - Slime
 [ http://www.slimeland.com/ ]

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>  well,I'd like to put forward a question,"How to Calculate or know the Focal
> Length of the perspective type Camera in POV-RAY3.6",can anybody be so kind
> to help me? 

WHile it is possible to include a lens into the rendering process, 
normally a pure raytracer implements a so called pinhole camera. As
such there is no focal length, everything from 0 to infinity is in
focus.

-- 
Paul Bourke
pdb(NOSPAM)swin.edu.au

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jiangzhijun wrote:
>  well,I'd like to put forward a question,"How to Calculate or know the Focal
> Length of the perspective type Camera in POV-RAY3.6",can anybody be so kind
> to help me? I am a new user to the POV,Thanks!
> 
	To make a povray camera that produces the same effect as a given
focal length on a 24x36 real life camera, you need to add the
following to the camera definition:

angle 2*atan2 (36, 2*f)*180/pi

	For a 50mm camera lens, this gives an angle of about 40.

		Jerome
- --
******************************
*      Jerome M. Berger      *
*  mailto:jeb### [at] freefr   *
*  http://jeberger.free.fr/  *
******************************
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> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> jiangzhijun wrote:
>>  well,I'd like to put forward a question,"How to Calculate or know
>> the Focal Length of the perspective type Camera in POV-RAY3.6",can
>> anybody be so kind to help me? I am a new user to the POV,Thanks!
>>
> To make a povray camera that produces the same effect as a given
> focal length on a 24x36 real life camera, you need to add the
> following to the camera definition:
>
> angle 2*atan2 (36, 2*f)*180/pi
>
> For a 50mm camera lens, this gives an angle of about 40.

Do you have a formula to set the aperture as well for focal blur? :-)  That
would be useful.

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"scott" <sco### [at] spamcom> wrote:

> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > jiangzhijun wrote:
> >>  well,I'd like to put forward a question,"How to Calculate or know
> >> the Focal Length of the perspective type Camera in POV-RAY3.6",can
> >> anybody be so kind to help me? I am a new user to the POV,Thanks!
> >>
> > To make a povray camera that produces the same effect as a given
> > focal length on a 24x36 real life camera, you need to add the
> > following to the camera definition:
> >
> > angle 2*atan2 (36, 2*f)*180/pi
> >
> > For a 50mm camera lens, this gives an angle of about 40.
>
> Do you have a formula to set the aperture as well for focal blur? :-)  That
> would be useful.

  Thanks for the above all, :)
  I am on my way to generate such a video sequence:A focus-length-fixed
perspective camera,moving along certain axis or direction,before some
object in the scene.
  I have done some expriments to recovery the focus-length of the above
camera,but was exhausted to find that the focus-length seems floating,Is
that real in POV? and how to fix the camera focus-length even when it moves
along?

       angle 2*atan2 (36, 2*f)*180/pi
  if this 'angle'  is fixed,does it mean that the focus length is fixed?

Post a reply to this message

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scott wrote:
> Do you have a formula to set the aperture as well for focal blur? :-)  That
> would be useful.
> 
	Not out of the top of my head. I'll think about it and let you know
if I find it.

		Jerome
- --
******************************
*      Jerome M. Berger      *
*  mailto:jeb### [at] freefr   *
*  http://jeberger.free.fr/  *
******************************
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jiangzhijun wrote:
>   I have done some expriments to recovery the focus-length of the above
> camera,but was exhausted to find that the focus-length seems floating,Is
> that real in POV? and how to fix the camera focus-length even when it moves
> along?

>        angle 2*atan2 (36, 2*f)*180/pi
>   if this 'angle'  is fixed,does it mean that the focus length is fixed?
> 
	If your only camera settings are "location" and "look_at", then the
field of view (focal length) will change when these values change.
The best way to control directly the FOV is with the angle keyword, e.g:

camera {
   location -z
   look_at  0
   angle    40
}

	For more details on camera parameters, I can only refer you to the
documentation (section 2.3.1):
http://www.povray.org/documentation/view/3.6.1/246/

		Jerome

- --
******************************
*      Jerome M. Berger      *
*  mailto:jeb### [at] freefr   *
*  http://jeberger.free.fr/  *
******************************
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