Smal question about aperture

[tomas_p]

Hi Radiance or all.

I have one smal question.
In which units is the aperture in Octane?
Are these examples valid or not?

F1 = 1,0000 oct.ap. (1/1)
F1,4 = 0,7143 oct.ap. (1/1,4)
F1,8 = 0,5556 oct.ap. (1/1,8)
F2,8 = 0,13571 oct.ap. (1/2,8)
etc....


Thanks

[radiance]

aperture radius in in cm.

Radiance

[tomas_p]

Thanks

So. I hope this is correct.

Octane aperture value = ( ( focal length in mm / lens aperture ) / 2) / 10

[colin]

just a quick thought radiance,

wouldn't it make more sense to use well known and established aperture parameters - rather then a "new" value unknown to most?
i know 2/2,8/4/5.6 etc. doesn't look as elegant as 1,2,3 - but i'd say i'm not the only one who grew accustomed to f-stops.
i guess what i'm trying to ask is if there's any chance you'd be willing to change octanes aperture values into f-stops?

what an elegant way to higjack a thread...
colin

[ieatfish]

If nothing else, maybe a setting to toggle between the two methods?

[ROUBAL]

There is a thing that I wanted to ask for some time and that I have forgotten :

If you look at the node named Mesh Preview Imager, you will find a cursor for F Stop, with The ISO cursor, and the Exposure cursor.

So, the Aperture cursor has probably an other effect...

For my own, my current theory is that in actual photo cameras, DOF is function of the Focal length, the F Stop value, the distance from the object in focus and the dimensions of the film plate or the sensor.

The smaller is the film plate or the sensor, the bigger is the DOF range. That's the reason why digital camera usually have a larger DOF range than classical cameras : their sensor is generally smaller that usual film plates formats.

I remember that someone asked why the film plate dimension was not present as a setting in Octane. This may be an answer : rather than adding a setting for the film plate dimension, the Aperture setting directly acts on the focus range, aka the DOF. I think that It is an other way to manage the formula in a more intuitive way, maybe more suitable for artists than photographers.

@Radiance : Any enlightment about this parameter would be welcome.

[tomas_p]

Hi all.

Here is a simple chart between angle of view (used in Octane > fov) and focal length of curent (Nikon) camera lens. Yu can put the focal length and F-stop to this equation. I hope is good.

Octane aperture value = ( ( focal length in mm / F-stop ) / 2) / 10


Regards
Tomas

[tomas_p]

Sorry
The chart

http://www.nikonlinks.com/unklbil/lens_angle_chart.htm

[ROUBAL]

@tomas_p : I was writing my post while you posted yours.

What do you think about my explanation ?

Your chart shows the angle of vision and doesn't uses the film plate dimensions. It is probably for 35mm format (24x36mm) only, but I'm not sure that it is really related to something usable within Octane.

[tomas_p]

Hi ROUBAL

I think, youre thought is not wrong in base, but I think with optics is it a bit more complicated.
Is a lot of objectives types and formats for cameras. ( fullframe kinofilm, kinofilm with crop factors, midle format like Hasselblad { other lens diameter }, large format like Sinar { other lens diameter } and many others ). I think, due to this is in Octane separate F-stop (darking efect of F-stop in real lens) and aperture (the aperture radius like in real lens in cm).

Regards