This page provides information on the Physical camera attributes that are part of the V-Ray Camera Attributes.
Overview
The VRayPhysicalCamera 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 VRayLight with physical units, or VRaySun and VRaySky.
Choosing the Physical camera option for a camera node in Maya creates the Extra VRay Attributes as a rollout in the Attribute Editor for the camera.
Adding the V-Ray Physical camera attribute will automatically enable the Treat as VRay Physical camera setting.
Physical Camera Attributes
Treat as VRay Physical camera – Causes the standard Maya camera to act as a VRay Physical camera, and enables the remaining parameters in this rollout.
Type – Determines the type of the physical camera to simulate. This mostly has an effect on the motion blur effect produced by the camera:
Still camera – Simulates a still photo camera with a regular shutter.
Cinematic camera – Simulates a motion-picture camera with a circular shutter.
Video camera – Simulates a shutter-less video camera with a CCD matrix.
Film gate (in mm) – Specifies the horizontal size of the film gate in millimeters. Note that this setting takes into account the system units configuration to produce the correct result.
Focal length (in mm) – Specifies the equivalent focal length of the camera lens. This setting takes into account the system units configuration to produce the correct result. Vertical film gate size is calculated by taking image aspect ratio into account (vertical film size = horizontal film size / aspect ratio). This parameter is available only when Specify FOV is set to Off.
Specify FOV – Specifies the source for the camera's field of view setting.
Off – The field of view is determined by the Focal length (in mm) parameter.
Specify – The FOV parameter becomes available for manual setting.
From Maya camera – The field of view is determined by the settings of the Maya camera.
FOV – A value for the camera's field of view when Specify FOV is set to Specify.
Zoom factor – Specifies a zoom factor. Values greater than 1.0 zoom into the image; values smaller than 1.0 zoom out. This is similar to a blow-up rendering of the image. For more information, see the Zoom Factor example below.
Distortion type – Determines what formula is used to calculate the distortion for the camera
Quadratic – This is the default distortion type. It uses a simplified formula that is easier to calculate than the Cubic method.
Cubic – This is the distortion type used in some camera tracking programs like SynthEyes and Boujou. If you plan on using one of these programs, use this distortion type.
Lens file – An external .lens file is used to determine the distortion for the camera.
Texture – A displacement map from Nuke can be used to determine the camera distortion.
Currently, Lens file distortion type is not supported with V-Ray GPU.
Distortion amount – Specifies the distortion coefficient for the camera lens. A value of 0.0 means no distortion; positive values produce "barrel" distortion, while negative values produce "pillow" distortion. This parameter is available only when Quadratic or Cubic is selected as the Distortion type. For more information, see the Distortion example below.
Lens file – The file used to calculate the camera distortion. This is only available when the Distortion type is set to Lens file.
Distortion map – The texture used to determine the camera distortion. This is only available when the Distortion type is set to Texture.
F-number – Determines the width of the camera aperture. For more information, see the Exposure Control: F-Stop (f-number) example below.
Horizontal/Vertical lens shift – Values other than 0 tilt the lenses to simulate 2-point perspective.
Guess vertical lens shift – Click to automatically set the Vertical lens shift parameter to achieve 2-point perspective.
Shutter speed – The shutter speed, in inverse seconds, for the still photographic camera. For example, a shutter speed of 1/30 of a second corresponds to a value of 30 for this parameter. For more information, see the Exposure Control: Shutter Speed (s-1) example below.
Shutter angle – Shutter angle (in degrees) for the cinematic camera.
Shutter offset – Shutter offset (in degrees) for the cinematic camera.
Latency – CCD matrix latency, in seconds, for the video camera.
ISO – Determines the film power (i.e. sensitivity). Smaller values make the image darker, while larger values make it brighter. For more information, see the Exposure Control: Film Speed (ISO) example below.
Specify focus – This allows you to specify a focus distance different from the camera target distance.
Focus distance – Sets the focus distance of the camera.
Exposure color correction – Specifies how the F-number, Shutter speed, and Film speed (ISO) settings affect the image brightness. For more information, see Exposure, Field of View and Focus Distance example above.
No Exposure – Shutter speed, F-number and ISO settings do not affect the image brightness;
Physical Exposure – Image brightness is controlled by the Shutter speed, F-number and ISO;
Exposure Value (EV) – Uses the Exposure value to control image brightness. Grays out the ISO parameter and uses Shutter speed and F-number values only for Motion Blur and Depth of field respectively.
White balance – A color that can be used to alter the image output. Objects in the scene that have the specified color appear white in the image. Note that only the color hue is taken into consideration; the brightness of the color is ignored. For more information, see the White Balance example below.
Exposure value – Controls the exposure value when the Exposure Value (EV) option is selected. Higher values make the render darker, whereas lower values make the render brighter.
Enable vignetting effect – When this option is enabled, the optical vignetting effect of real-world cameras is simulated. For more information, see the Vignetting example below.
Vignetting amount – Specifies the amount of the vignetting effect, where 0.0 is no vignetting and 1.0 is normal vignetting.
Enable Bokeh effects – Defines the shape of the camera aperture. When this option is disabled, a perfectly circular aperture is simulated. When enabled, a polygonal aperture is simulated. This option has an effect when depth-of field is enabled.
Number of blades – Specifies the number of blades of the polygonal aperture.
Blades rotation (in radians) – Defines the rotation of the blades.
Center bias – Defines a bias shape for the bokeh effects. Positive values make the outer edge of the bokeh effects brighter; negative values make the center of the effect brighter.
Bokeh anisotropy – Values other than 0 stretch the bokeh effect horizontally or vertically to simulate anamorphic lenses. If you want the ratio of height to width of the bokeh to be k:1, then the value for anisotropy should be sqrt(1/k)-1. For example, for anamorphic bokeh, which is 2.39:1, the anisotropy value should be -0.353.
Enable Depth-of-field – Turns on depth of field sampling. For more information, see the Depth Of Field (DOF) example below.
Enable Motion blur – Turns on motion blur sampling. Keep in mind that motion blur is not rendered with V-Ray IPR. For a visual aid, see the Motion Blur (MB) example.
Aperture map – Specifies a texture to define the shape of the aperture.
Affects exposure – When enabled, the size and shape of the aperture specified in the Aperture map affects the exposure of the final image.
Cat's eye bokeh – Controls the strength of the optical vignetting, also known as "cat's eye" vignetting. This effect is due to the fact that the shape of the bokeh highlights resembles the shape of the aperture. As the distance to the optical axis increases, the bokeh highlights are progressively narrowed and begin to resemble the shape of a cat's eye. The larger the distance from the image center, the narrower the cat's eye becomes. Optical vignetting tends to be stronger in wide angle lenses and large aperture lenses, but the effect can be noticed with most photographic lenses.
Rolling shutter mode – Specifies whether the rolling shutter effect is enabled and the direction of the shutter. The Rolling Shutter effect options are active only if the Motion Blur is enabled. For more information, see the Rolling shutter mode example.
Disabled
Top to bottom
Bottom to top
Left to right
Right to left
Rolling shutter duration – The time for the shutter to pass through the image in 1/seconds.
Camera shader texture – Allows a V-Ray OSL texture to be attached to the physical camera. OSL textures allow additional options to be added to the camera such as blur, color and others. Note that this options is not supported when rendering in the Viewport IPR.
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.
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.
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.
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, for instance, looks best when captured with around 100 ISO.
Example: Zoom Factor
This parameter determines the zooming (in and iut) of the final image. It doesn't move the camera forward nor backwards.
The images in this example show the effect of changing the Zoom factor. The following constant settings were used for some parameters: Exposure is on, F-Number is 8.0, Shutter speed is 60.0, Film speed (ISO) is 200.0, Vignetting is on, White balance is white.
Zoom factor = 0.5
Zoom factor = 1.0
Zoom factor = 2.0
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.
Distortion Amount is 1.0, Distortion type is Quadratic
Distortion Amount is -1.0, Distortion type is Quadratic
Distortion Amount is 1.0, Distortion type is Cubic
Distortion Amount is -1.0, Distortion type is Cubic
Example: Exposure Control: F-Stop (f-number)
Note: All the images from the following examples are rendered using the VRaySun and VRaySky 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. See the Depth of Field Example for more information.
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, Film speed (ISO) is 200, Vignetting is on, White balance is white.
F-Number = 4.0
F-Number = 5.6
F-Number = 8
Example: Exposure Control: Shutter Speed (s-1)
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 would be. In reverse - if the exposure time is shorter (high shutter speed value), the image would get 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, Film speed (ISO) is 200, Vignetting is on, and White balance is white.
Shutter speed is 10.0
Shutter speed is 60.0
Shutter speed is 125.0
Example: Exposure Control: Film Speed (ISO)
The Film speed (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 Film speed (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.
Film speed (ISO) is 200
Film speed (ISO) is 400
Film speed (ISO) is 800
Example: Exposure, Field of View and Focus Distance
The focus distance of the physical camera (as specified by either the Target distance or the Focus distance parameter) affects the exposure of the image and the field of view for the camera, especially if the focus distance is close to the camera. This is an effect than can be observed with real-world cameras as demonstrated in the images below.
The set up is a white board with a small black rectangle and a camera in front of it. Notice how changing the focus distance produces images with different brightness even though the illumination and all other camera parameters are the same in both cases. Also notice the change in the field of view.
The camera is focused on the white board; the grey color is approximately RGB 104, 104, 104.
The camera is focused at infinity; the grey color is approximately RGB 135, 135, 135.
Side view of the camera focused on the white board.
Side view of the camera focused at infinity.
Example: White Balance
Using the White balance color allows additional modification of the image output. Objects in the scene that have the specified color will 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, Film speed (ISO) is 200.0, and Vignetting is off.
White balance is white (255, 255, 255)
White balance is blueish (196, 226, 255)
White balance is warmer (240, 200, 114)
Example: Vignetting
This parameter control the optical vignetting effect of real-world cameras.
Example: Depth Of Field (DOF)
To enable the DoF effect you need to turn on the Depth of field option DoF & Motion blur rollout 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. And at last but not least the Focus distance determines which part of the scene will be actually on focus. To get the focus near, you would 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 on, F-Number is 1.0, Shutter speed is 4000.0, Film speed (ISO) is 100.0, Vignetting is off.
Depth of field is off
Depth of field is on, Focus distance is 7.30 m
Depth of field is on, Focus distance is 4.34 m
Example: Motion Blur (MB)
To enable the motion blur effect, you need to enable the Motion blur option in the DoF & Motion blur rollout 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 will produce more motion blur, as the movement of the object is tracked over a longer time. In reverse, short shutter speeds will 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.
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 on, Film speed (ISO) is 200.0, and Vignetting is on.
Motion blur is off
Motion blur is on, F-Number is 8.0, Shutter speed is 80.0
Motion blur is on, F-number is 16.0, Shutter speed is 20.0
Example: Rolling shutter mode
The first image only has motion blur applied. Rolling shutter mode is Disabled. The second image has Rolling shutter mode set to Top to bottom.
