Join Brian Bradley for an in-depth discussion in this video A closer look at the exposure controls, part of SketchUp: Rendering with V-Ray 3.
- [Instructor] In the real world, photographers use exposure at its most basic level to control brightness levels in the images that they are shooting and so hopefully create images that at least look technically correct. Going beyond that of course, they also use exposure to help elicit an emotional response from anyone who may be viewing their images, and although we will here be looking at the controls of the technical side of exposure in V-Ray, it is good to keep in mind that these same controls can also be used to help shape the final aesthetic or feel of the rendered images that we are producing.
Now in Chapter Two of this course, we looked at how the sunlight tool in V-Ray can be used to create a physically accurate daylight simulation given that it has been designed to create the same level of illumination, the same virtual energy output as the real sun and sky. In simple terms then, this is a very, very bright light source inside of V-Ray. In fact, if we were to render a sunlit scene here without the use of exposure, what we would get is an image that essentially looked like a nuclear explosion in progress.
To demonstrate what I mean by that, let's go into the Settings tab on the asset editor and in the Camera rollout, set the exposure value to zero, so essentially turning off exposure control for the rendering camera. If we take a render now, you can see exactly what I meant, nuclear explosion in progress. Clearly then, learning to use the exposure controls that we have will be an extremely important skill to master whenever we want to render with the V-Ray engine. Of course, there are other ways in which we could control illumination in a scene such as this.
We could for instance jump into the Lights tab and in the sunlight controls, set the intensity value way down to something like 0.00025, which when we render, would give us a fairly decent level of exposure for the scene. The problem with doing that is that we essentially break the physicality of this well-designed lighting system. If we want realistic light behavior in our scenes then, which can help us avoid unnecessary noise problems in an image for instance, we should try to keep the physicality of the system intact, at least wherever possible, which is why, more often than not, making use of V-Ray's exposure controls is the best way to handle illumination levels in our scenes.
Taking a cue from our primer on exposure values exercise then, a good starting point for an EV value here would probably be around about the 15 mark with 15 being typical of a clear, bright, sunny day. Given that we are using a mid-morning setting here however, and are in an enclosed space, let's reset our sunlight intensity to one, go back to an EV setting of 12, and then switch the standard camera UI over to advanced mode. What we can see now is that we are currently using an ISO value of just short of 470 here with f-stop and shutter speed values of eight and 300 respectively.
Watch what happens though if I switch the UI back again, set an EV value of zero and then jump back to advanced mode. We are now using an ISO value that numbers in the millions. This is because rather than being a true EV system which, as already noted, will throw up a variety of shutter speed and aperture settings for a single exposure value, what we are actually working with here is an Auto ISO mode, meaning V-Ray is making exposure changes by updating only the ISO value on the camera which makes perfect sense really, seeing as ISO is the only part of the exposure triangle that doesn't control other effects on the V-Ray camera.
If we go back to our exposure setting of 12 then and take a render, the result that we get shows our system is working nicely with the target EV giving the expected feel to our image. Of course, if we feel much more comfortable using the more standard camera controls of ISO, f-stop, and shutter speed, then we can most certainly go ahead and do that.
- Gamma handling in V-Ray 3 for SketchUp
- Working with interactive rendering
- V-Ray light types
- Working with irradiance mapping
- Rendering animations
- Working with the V-Ray camera
- Using the Materials UI
- V-Ray FX tools
- Stereoscopic 3D rendering
- Using V-Ray objects