--- title: "V-Ray Physical Camera" canonical: "https://documentation.chaos.com/space/VRAYHOUDINI/113281488/V-Ray%20Physical%20Camera" format: markdown --- This page provides information on the V-Ray Physical Camera parameters that can be added to standard Houdini cameras. ## **Overview** --- The V-Ray Physical Camera allows you to use real-world parameters to set up the virtual CG camera (e.g. f-stop, lens focal length, etc). This gives you access to lens properties such as aperture (F-Stop) and shutter speed as well as depth of field, motion blur, and more. V-Ray Physical Camera also makes it easier to use light sources with real-world illumination such as[ V-Ray Lights ](https://docs-chaos.atlassian.net/wiki/spaces/VRAYHOUDINI/pages/113280263)with physical units or [V-Ray Sun Light](https://docs-chaos.atlassian.net/wiki/spaces/VRAYHOUDINI/pages/113279170). To add V-Ray Physical Camera parameters to a standard Houdini camera, use the **Physical Camera** button on the [V-Ray Shelf.](https://docs-chaos.atlassian.net/wiki/spaces/VRAYHOUDINI/pages/113280420) This will add a new tab to the selected Camera's parameters. ## **Parameters** --- ## **Main** --- --- ### **Aperture F-number vs Shutter Speed vs ISO** **Cheat Sheet** 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. - F-number determines the size of the opening in the camera lens. What the number refers to is the ratio between the aperture's focal length and the actual diameter of the aperture. A smaller F-number means a larger aperture. The larger the Aperture, the brighter the scene becomes but that also introduces more [Depth of field](#DOF). - Shutter Speed determines how long the lens stays open when taking the photo. The numbers refer to fractions of a second. The slower the Shutter Speed, the brighter the scene becomes but that also introduces [Motion Blur](#motionBlur). - ISO determines the camera's sensitivity to light in the scene. Lowering the ISO means that more light is needed to achieve good lighting. Increasing the ISO means that less light is needed to achieve good lighting. A day scene, lit with a [V-Ray Sun](https://docs-chaos.atlassian.net/wiki/spaces/VRAYHOUDINI/pages/113279170), for instance, looks best when captured with around 100 ISO. > Macro (anchor) ## **Depth of Field** --- > Macro (anchor) ## **Motion Blur** --- > ℹ️ 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. > ℹ️ > ℹ️ 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. ## **Distortion** --- > Macro (anchor) --- ### ** ** **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. ** ** > Macro (anchor)   --- ** ** ### **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. > Macro (anchor) --- ### **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](#ExampleMotionBlur). 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. > Macro (anchor) --- ### **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. > Macro (anchor) --- ### **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. > Macro (anchor) --- ### ** ** **Example: Vignetting** > Macro (anchor) --- ### **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. --- > Macro (anchor) ### **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. > ℹ️ In this example, the falling roof tiles are moving faster than the flower pot, which causes the difference in the motion blur effect. For the images in this example, the following constant settings were used for some parameters: **Exposure **is set to **Exposure Value**, **Exposure Value** is set to 7 and **Vignetting **is on.