VRay for Rhino Manual

The Physical Camera feature allows the camera’s reaction to light to mimic that of a camera in the real world. This means a much more natural reaction to light as well as an added dimension of control over the lighting of your scene. There are also added ways to adjust your rendered result.

Type of Camera

In V-Ray’s physical camera parameters you will see that there are three options within the types of cameras. The first is a still camera, and the other two, cinematic and video, are for use with animations. We will only be concerned with the still camera, as the others are used to do camera matching with existing footage. The still camera may still be used with animations, and produces great results.

Exposure

In the real world, exposure is the act of light affecting the film or a sensor, and there are three aspects that dictate the resulting affect of the light. The first is known as ISO speed. The ISO speed refers to the sensitivity of the film or sensor. A larger ISO speed corresponds to a greater sensitivity to light. The second aspect affecting the exposure is the aperture. This corresponds to the size of the opening that allows light to pass to the film or sensor. This value is referred to as F-stop, and smaller values equate to a larger opening, and thus more light. The last component that will contribute to the exposure is the Shutter Speed. The shutter speed is the amount of time that the light is allowed to affect the sensor. A longer amount of time will allow in more light, leading to a brighter image.

Adjusting Exposure

Now that we know what determines the exposure how do go about properly adjusting it for our image. This can be done through either of the three parameters: ISO, Aperture, or Shutter Speed. In order for these parameters to have an affect on the exposure of the image Exposure must be checked in the physical camera settings. Depending on some of the other affects that are being used adjusting the camera via one parameter might be more appropriate than another.

Using Aperture

When using aperture to adjust exposure remember that there is an inverse relationship between the value and the result. Meaning that a small value will increase the brightness of your scene, and that a large value will decrease the brightness of your scene. If you have depth of field enabled, then the aperture value will determine how much depth of field will be in your scene. A smaller value will create a narrow depth of field, in which objects will have to be closer to the focal distance of the camera in order to stay in focus. A larger value will create a greater depth of field. This will allow objects to stay in focus even if they are farther away from the focal distance. If you are trying to get achieve a particular depth of field, then it is recommended that you adjust the exposure through the shutter speed or the ISO setting.

Using Shutter Speed

Shutter speed can be another good way to adjust the exposure of your image. The parameter itself actually expresses itself as 1/x. In other words inputting a value of 4 actually means a shutter speed of one quarter of a second. Therefore a larger value actually means that the shutter speed is faster, and that will translate to a darker image. If you are doing any animation, with either moving objects, a moving camera, or both and also have motion blur enabled then the shutter speed will have a direct effect on the amount of motion blur. A longer shutter speed will cause a greater amount of motion blur, where as shorter shutter speed will decrease the amount of motion blur. The amount of blurring will also be determined by the speed of the objects as well. If you are trying to have a certain amount of motion blur, then it would be advised to test different shutter speeds until the right amount of blurring occurs, and then adjust for exposure with either aperture or ISO value.

Using ISO

The ISO value is extremely useful for exposing a scene. With rendering the ISO value does not have any side effects or byproducts like aperture or shutter speed. This allows you to tailor the other parameters to the needs of your scene, and the ISO can act as the determining factor in the final exposure of the image. This would be extremely useful to properly expose a scene with both depth of field and motion blur. The ISO values are also have a linear relationship which is not the case with both aperture and shutter speed. For ISO values a larger number will also mean a brighter image, which may be easier to remember.

Adjusting white balance

The white balance feature allows you to compensate for the color of the lighting of a scene by determining which color V-Ray interprets as white. This can be very useful for counterbalancing the color of the V-Ray sun, accurate color matching for placing rendering in a photo, or a quick and simple adjustment of the tone of an image. Typically colors used for adjusting the white balance of an image are lighter and under saturated.