I'm aware that pov's camera is a pinhole.

I'm starting out on a technical rendering exercise, where I need to make
pov's output look as much like a real camera.

What I know, is my image sensor size, and the focal length of a given lens
in our system, and what field of view it gives.

I would like to be able to vary the focal length, and get the corresponding
change in field of view, as well as the appropriate distortion as we get
into the lenses that have FOVs like 120 degrees.

Is this available as a macro or .inc somewhere?

Thanks

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> I'm aware that pov's camera is a pinhole.
>
> I'm starting out on a technical rendering exercise, where I need to make
> pov's output look as much like a real camera.
>
> What I know, is my image sensor size, and the focal length of a given lens
> in our system, and what field of view it gives.
>
> I would like to be able to vary the focal length, and get the 
> corresponding
> change in field of view, as well as the appropriate distortion as we get
> into the lenses that have FOVs like 120 degrees.
>
> Is this available as a macro or .inc somewhere?

You can set the horizontal FOV with the angle keyword in a camera.

Focal blur can be defined with the aperture, blur_samples, focal_point,
confidence, and variance keywords. With the right settings, and good
objects the render is nearly indistinguishable from a photo.

Aperture varries in the same manner as f-stops. An aperture of 0.125
very roughly corresponds to an f/8 setting. However, since the POV
simulation of focal blur is not based on a model of a lens, this is not
100% correlation. In a POV camera the depth of field varies
*differently* in relation to the distance to the focal_point than how it
varies in a RL camera.  POV ray-traces from the camera to the
scene and returns the color, with focal blur it just uses some
Montecarlo randomization to sample some extra ray-traces to find
an average, there is no diminishment of light at a distance like in a
RL camera.  The number of samples per pixel to take are set with
blur_samples, confidence, and variance; the number of ray-traces
has a big impact on render speed.

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Here's a something that may help with DOF.
http://www.wozzeck.net/images/index.html

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"Tim Attwood" <tim### [at] comcastnet> wrote:

> ,,,,since the POV
> simulation of focal blur is not based on a model of a lens, this is not
> 100% correlation. In a POV camera the depth of field varies
> *differently* in relation to the distance to the focal_point than how it
> varies in a RL camera.

It would be interesting--and visually useful--if  POV offered an "alternate"
type of focal blur, one that blurred the image only from the camera to the
object/point of interest, then kept the distance beyond that sharp. I'm
thinking along the lines of "hyperfocal distance" in a real camera lens,
but more extreme. I believe (and this is subjective, of course) that it
would help to make the blurring more realistic. As for outdoor scenes on a
bright and sunny day. It would seem to me that implementing such a blur
would *only* (?) require that image pixels "beyond" the point of  max
sharpness not be jittered. As it is now, pixels are jittered (equally?) in
*both* directions relative to the max sharpness point.

Ken W.

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