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To add V-Ray Physical Camera parameters to a standard Houdini camera, use the Physical Camera button on the V-Ray Shelf. This will add a new tab to the selected Camera's parameters.
UI Path:
||Select camera|| > V-Ray Shelf > Physical Camera button
||Select camera|| > V-Ray menu > Object Properties > Physical Camera
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Parameters
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Main
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Aperture F-number vs Shutter Speed vs ISO
Cheat Sheet
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The main options that control the brightness of a V-Ray Physical camera are Aperture F-number, Shutter Speed and ISO. They affect each other and you need to balance them according to your scene. Keep in mind that these settings do not correspond to those of a real-life camera. They apply only to the V-Ray Physical camera.
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Depth of Field
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Motion Blur
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When rendering Alembic file sequences (e.g. file.$F4.abc), V-Ray expects a velocity attribute for creating the Motion Blur effect. To generate the "v" attribute prior to export, use a Trail SOP. The "Geometry Velocity Blur" option has to be set to "Velocity Blur" under the Render → Sampling tab of the Geometry node. This limitation is not present when rendering a sequence stored in a single Alembic file (e.g. file.abc). V-Ray is able to interpolate between the neighboring geometry samples, provided that the topology/point count of the contained geometry does not change. |
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Distortion
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Example: Distortion
The difference between the two types of distortion is slightly visible. The Cubic type should be used in some camera tracking programs like SynthEyes, Boujou, etc.
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Example: F-Stop (F-Number)
Note: All the images from the following examples are rendered using the V-Ray Sun and Sky set with their default parameters.
The F-Number parameter controls the aperture size of the virtual camera. Lowering the F-Number value increases the aperture size and so makes the image brighter since more light enters the camera. In reverse, increasing the F-Number makes the image darker, as the aperture is closed. This parameter also determines the amount of the Depth of Field (DOF) effect.
The images in this example show the effect of changing the F-Number. The following constant settings were used for some parameters: Exposure is on, Shutter Speed is 60.0, ISO is 200, Vignetting is on, White Balance is white.
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Example: Shutter Speed
The Shutter Speed parameter determines the exposure time for the virtual camera. The longer this time is (small shutter speed values), the brighter the image is. In reverse - if the exposure time is shorter (high shutter speed value), the image is darker. This parameter also affects the motion blur effect, see the Motion Blur Example.
The images in this example show the effect of changing the Shutter Speed. The following constant settings were used for some parameters: Exposure is on, F-Number is 8.0, ISO is 200, Vignetting is on, and White Balance is white.
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Example: ISO (Film Speed)
The ISO parameter determines the sensitivity of the film and consequently the brightness of the image. If the ISO value is high (film is more sensitive to light), the image is brighter. Lower ISO values mean that the film is less sensitive and produces a darker image.
The images in this example show the effect of changing the ISO. The following constant settings were used for some parameters: Exposure is on, Shutter Speed is 60.0, F-Number is 8.0, Vignetting is on, and White Balance is white.
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Example: White Balance
Using the White Balance color allows additional modification of the image output. Objects in the scene that have the specified color appear white in the image. E.g. for daylight scenes this should be peach color to compensate for the color of the sun light, etc.
The images in this example show the effect of changing the White Balance. The following constant settings were used for some parameters: Exposure is on, F-Number is 8.0, Shutter Speed is 200.0, ISO is 200.0, and Vignetting is off.
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Example: Vignetting
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Example: Depth Of Field (DOF)
Enable DoF effect from the Depth of Field tab of the physical camera. The effect is most strongly seen when the camera is close to an object, for example when doing a macro photo. For a strong DoF effect, the camera aperture must be open wide (i.e. small F-Number value). That may lead to a very burnt and bright image, so to preserve the same illuminosity over the whole image, the Shutter Speed must be shortened. Last but not least the Focus Distance determines which part of the scene is actually on focus. To get the focus near, you need a small value and reverse - higher value for far focus.
For the images in this example, the following constant settings were used for some parameters: Exposure is set to Exposure Value, F-Number is 1.0, Exposure Value is 7.0, Shutter Speed is 125, Vignetting is off.
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Example: Motion Blur (MB)
Enable the Motion Blur effect from the Motion Blur tab of the physical camera. The amount of motion blur is determined by the speed of the moving object itself as well as the Shutter Speed setting of the camera. Long shutter speeds produce more motion blur, as the movement of the object is tracked over a longer time. In reverse, short shutter speeds produce less motion blur. Keep in mind that to preserve the same brightness over the whole image, the F-Number value has to be corrected as well.
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In this example, the falling roof tiles are moving faster than the flower pot, which causes the difference in the motion blur effect. |
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