Introduction


  • This lesson will take you through creating and using a V-Ray Physical Camera
  • The information centers around vrayPhysicalCamera extra attributes
  • This lesson topic is approximately 25 minutes in length
  • Lesson covers all 3 Learning Cycles for the Lesson Topic – Lecture, Demonstration, and Activity

 


 

Contents


Overview
Available Materials
Lecture
Demonstration
Activity                                 
Additional resources     
                        


Overview


Goal - This lesson will give you a basic understanding of the V-Ray Physical Camera so you can properly set it up and manage your exposure.

Objective – We will be able to create and configure a V-Ray Physical Camera for your 3D scenes            

Outcome – You will understand the basics of the V-Ray Physical Camera and how it helps use light sources with real-world illumination (VRayLight with physical units or VRaySky and VRaySky

 


 

Available materials


To set up the lesson follow the links below and download all available materials.

Lesson plan download
Presentation (Lecture) download
Demonstration tutorial download                                       

Scenes & Assets download                                       

 

Lecture



1. Terminology

 The V-Ray Physical Camera is based on a real-world camera so the concepts of photography apply. Here’s some terms to be aware of when thinking about the Physical Camera.

  • Aperture
    • The hole in a camera lens that allows light to travel through to the inside of a camera
    • Normally referred to by the F-Stop or F-number
  • Lens Distortion
    • A slight warping on the edges of an image normally from the physical properties of a wide-angle lens
  • ISO (International Standards Organization)
    • Main governing group that standardizes sensitivity ratings for camera sensors
    • A camera’s sensor (or film) sensitivity to light during the exposure process
  • White Balance
    • A calibration process to adjust color temperatures in lights (or film stock) that makes sure white objects appear white
  • Shutter Speed (or Exposure Time)
    • The length of time when the film or digital sensor inside the camera is exposed to light
    • The camera’s shutter is open to take a picture

2. Physical Camera


 а) Aperture

  • Referred to as F-number in V-Ray Physical camera
  • The opening in the camera lens that allows more or less light to pass through into the camera
    • Almost like the pupil of our eyes
  • The smaller the opening the smaller the amount of light in the exposure
    • The image will be darker unless other adjustments are made to areas like Shutter Speed or the ISO
    • Changing from one Stop to the next (F/11 to F/8) lets in twice as much light during the exposure
    • The difference between F/8 and F/4 is not twice, it’s 4 times as much light
  • Plays a huge role on Depth of Field
    • The larger the opening (smaller F-number) the shallower the focus area is in depth
    • The smaller the opening, the more distance between objects that are still in focus

 

 

b) Shutter Speed
  • The amount of light that reaches the film or image sensor is proportional to the exposure time
    • 1/500th of a second will let half as much light in as 1/250th
  • Faster Shutter Speeds can capture fast moving objects with less motion blur
    • Action sports shots, a moving car, etc.
  • Slower Shutter Speeds allow more light into the camera during the exposure process
    • Other adjustments to the camera (F-Stop or ISO values) need to be made to maintain proper exposure
  • NOTE: “Proper Exposure” can be subjective but normally refers to an image that is considered in the middle between under exposed (too dark) and over exposed (too bright)

 

 


c) ISO
  • The higher the number the less light is needed to expose an image
    • Outside on a bright, sunny day a lower ISO (like 100) would be used to get proper exposure
    • At night or in a dark room, a higher ISO would be needed to expose the image properly
  • Less sensitive rated film stock (ISO 100 or 200) need a longer exposure time (slower Shutter Speed) or a larger aperture (lower F-number) to compensate for proper exposure
  • In the real world, higher ISO values will introduce more grain or noise to the image
    • Luckily, in the our 3D scenes, we don’t have to worry about this negative effect

 

 


d) Exposure Value (EV)
  • A number that represents a combination of a camera’s Shutter Speed and F-number, so that all combinations will make the same exposure have the same EV
  • Exposure Value is also used to indicate an interval on the photographic exposure scale, with a difference of 1 EV corresponding to a standard power-of-2 exposure step, commonly referred to as a Stop
  • Although all camera settings with the same EV should give the same exposure, they do not necessarily give the same picture
    • This is not a problem in 3D because all the camera components are virtual and will render the same results as opposed to physical objects that could have slight differences when they were manufactured

 

e) Focal Length
  • The distance between the lens’s glass and the film/sensor inside a camera (measured in millimeters)
    • Short distances are referred to as wide-angle lenses because of their angle of view
    • Long distances are referred to as telephoto lenses and compress the space between subjects and their backgrounds
  • Natural viewing angles are normally in the range between 35mm and 55mm
  • With short focal lengths, perspective is exaggerated, while long focal lengths flatten perspective

 

 


f) White Balance
  • Color balance is the global adjustment of the intensities of the colors (RGB)
  • A goal of this adjustment is to render specific colors – particularly neutral colors – correctly
    • The general method is sometimes called gray balance, neutral balance, or white balance
  • Color balance changes the overall mixture of colors in an image and is used for Color Correction
    • Generally speaking, you want to balance the amount of each primary color so colors like white will appear correct or pleasing
  • Some factors that can affect this is the color temperature of lights
    • Warm colored lights (3200° K) can appear white if balanced right
  • In the real-world of film, different stock is balanced for daylight (outdoor) use of Tungsten (indoor) and will create a natural white when used with the correct lighting temps.

 

 


g) Physical Camera Overview

  • To convert an existing Maya camera to a V-Ray Physical Camera, we add the Physical Camera Attribute from the menu in the Attribute Editor
    • The camera’s shape node must be selected
  • This will add Extra V-Ray Attributes to the bottom of the Attribute Editor
    • Camera is not a V-Ray Physical camera until the checkbox Treat as VRay Physical camera is Enabled
  • The Camera settings (extra attributes) override some of the Camera settings from the V-Ray Render Settings
    • These settings control the way geometry is projected into the image
    • Allows each camera to have different render settings

 


  • Type
    • Still camera – simulates a still photo camera with a regular shutter
      • Use the Shutter speed setting for exposure time
    • Movie camera – simulates a motion-picture camera with a circular shutter
      • Uses the Shutter angle and Shutter offset attributes
    • Video camera – simulates a shutter-less video camera with a CCD matrix
      • Uses the Latency attribute
  • F-number – determines the width of the camera aperture
  • Shutter speed – the speed of the camera shutter in inverse sec.
    • If the shutter’s speed was 1/30s the value of the parameter would be 30
  • ISO – determines the film power (sensitivity)
    • Smaller values make the image darker, larger values make it brighter
  • White balance – allows additional modification of the image output
    • Objects in the scene that have the specified color will appear white in the image
    • Note: Only the color hue is taken into consideration; color brightness is ignored

 

 


h) Focal Length
  • 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 accounting image aspect ratio (vertical film size = horizontal film size / aspect ratio)
    • With short focal lengths, perspective is exaggerated, while long focal lengths flatten perspective

 

 

Focal length: 120mm

Focal length: 300mm

 

 

i) F-number
  • Lowering the F-number value will actually make the image brighter
    • The camera aperture is being opened, so more light is making it’s way into the camera
  • Plays a large role in Depth of Field
    • For more details, see the Physical Camera – Depth of Field and Motion Blur Training topic

 

 

F-number: 1.4

F-number: 2.8

 


j) Shutter Speed
  • Determines the “exposure time”
    • Attribute value is expressed as a fraction, with this value being the denominator
      • A value of 10 means 1/10 of a second; a value of 5 means 1/5 of a second
    • The longer this time is (small shutter speed value) - the brighter the image would be
    • In reverse - if the shutter speed is shorter, the image would get darker (high shutter speed value)
  • Plays a large role in Motion Blur
    • For more details, see the Physical Camera – Depth of Field and Motion Blur Training topic

 

 

Shutter speed: 10

Shutter speed: 5

 

 

k) ISO
  • Determines the sensitivity (brightness) of the image
    • If the film speed (ISO) is high (more sensitive to the light), the less light is needed to expose the image
    • Higher values are usually used for "night shot" images

 

 

ISO: 20

ISO: 1.25

 


 


Conclusion



 

a) Aperture
  • The pupil of the camera, allowing more or less light in
b) ISO
  • A measurement of how sensitive a camera’s sensor (or film) is to light
c) Shutter Speed
  • How fast the camera is open to allow what’s in front of the camera to be exposed to the sensor (or film)
d) White Balance                    


Demonstration



Time to see it work!

Watch while I demonstrate how to adjust the camera settings on our V-Ray Physical Camera
Demonstration tutorial   

 

                         

 


Activity



Time to do it yourself!

Use the provided scene file to learn how the different settings within the V-Ray Physical Camera will effect your renders.
We have also provided a final scene for your reference.

 

 


Dialing in the right values

  • Treat as VRay Physical camera: Enabled
  • Type: Still camera
  • Focal length: (animated)
  • F-number: 1.4
  • Shutter speed: 10
  • ISO: 20

 

                                           

 


Additional resources


Find more training resources listed below: