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When it comes to adding a photographic depth-of-field effect to our renders, there are a couple of options available to us whilst rendering with V-Ray in SketchUp. We could for instance render out a Z-Depth G-Buffer image that could be used in a post-production application such as Photoshop to add blur after the fact. But if for some reason we need physically accurate depth of field, then we will need to use to V-Ray Physical Camera and its built-in depth-of-field capabilities. When we are looking to create in-scene effects such as depth of field with the V-Ray Physical Camera, we really need to keep in mind the fact that many of the choices we make for our camera setup, such as the focal length of our lens, camera placement for composition, lighting, and exposure requirements, all of these will affect how we create and ultimately control depth of field in our scene.
We also have a choice over the behavior of our V-Ray Physical Camera. It can be used exactly like a real camera in that depth of field is always a factor of the focal length, or we can override this behavior for a simpler setup and a more artistic, rather than realistic, approach to creating the depth-of-field effect. Because we do have this flexibility, we should note that any numeric values we work with in this video really are specific to the scene and the shot that we have composed.
You will need to adapt the values to work with the exposure of your scene, the focal length of your lens, and the type of depth of field you want in the shot. But perhaps one of the first things that we will need to decide is just what the point of focus is in our depth-of-field shot. In other words, what do we want in and what do we want to be out of focus? In our case we're going to work with our pool ornament as the in-focus part of the scene and we're going to create a subtle depth-of-field effect on our table. Of course we do need to go and enable depth field on our V-Ray Physical Camera, so let's come into the Options Editor, into the Camera rollout, and if we scroll down, you can see we have the depth-of-field controls and we can just switch that on.
A problem I have at the moment is that in the free version of SketchUp we actually don't have any easy way of measuring the distance from our camera in the scene to our point of focus, to our garden ornament. There are indeed free scripts that will allow us to measure the distance from our SketchUp camera to certain points in our scene. As we don't have any of those scripts installed though, we are going to be working with just the tools available with the default SketchUp and default V-Ray installs. Because that is the case, as well as turning on our depth-of-field effect, we also want to go and enable this Override Focal Distance control.
This will allow us to set a specific distance in our scene from the camera, at which our point of focus resides. What we can do now is engage in a little bit of educated guessing with the help of SketchUp's Tape Measure tool. The first thing I want to do is come and dismiss our Options dialog and I want to come over to SketchUp Zoom tool, because I want to reset my camera view to a 50 mm lens. This setting roughly approximates human vision, and it will allow us to make a rough estimate of where, behind this table, our camera is positioned.
So if I just left-mouse-click to select the Zoom tool and then just enter 50 mm on my keyboard and use the Enter or Return key, you can see we have now set a 50 mm focal length in our view. Now, as we say, we can roughly tell where, behind the table, our camera might be. Because we of course need to measure the distance from our pool ornament to the approximate position of our camera, we are going to use SketchUp's Tape Measure tool. First of all I want to come up to the Camera menu, come to Standard Views, and go to a Top view.
Then I just want to middle-mouse-scroll out and then grab the Hand tool and just pull everything into place, just so that we can use the Tape Measure tool very easily. If we go and grab that tool, we can take a measurement for ourselves. So, first click to approximate where our point of focus is in the scene. Then if I just use the left arrow key on my keyboard, I can constrain to the green axis, and we can take a rough estimate of where in the scene we think our camera is. So if we say something around about there, we have a measurement then of roughly just short of 48 feet, which is what I will round things up to.
To dismiss the Tape Measure tool, I am just going to press once on my spacebar. Now before I go and enter any values in our depth-of-field controls, I do just want to click on our depth-of-field camera tab here, just to reset our view. This of course takes us back to a 65 mm lens as well. Now with that set, I can go back into the Options Editor and we can work with our Override Focal Distance parameter. One thing we do need to keep in mind about this Override parameter is that it works in scene units, so we need to enter a value in inches into this field.
Do bear in mind that no matter what display unit we are currently using, SketchUp behind the scenes always works in inches, and this is the measurement that this particular parameter will always require. So, a quick use of the calculator will tell us that 48 feet is the equivalent of 576 inches. So now we have our point of focus set in the scene, but of course we don't have our depth-of-field effect. Just as with a real camera, we need to set our F Number, or F stop value, so that it will give us a depth of field effect in the scene.
In this instance, I am going to set a value of 2.2 in here. Of course, something we need to keep in mind is that with this Exposure option checked, our F Number is also handling exposure in the scene. For this reason then, we're going to need to compensate now for the change in brightness values by altering one of the other exposure parameters. As the ISO value doesn't really control any other effects on the V-Ray Physical Camera, generally speaking, this is the parameter that I choose to work with.
In this instance, we are going to set it all the way down to a value of 5. Now we should have a scene that is ready to render with a depth-of-field effect enabled, so let's dismiss our dialog and take another test render to see if that is the case. And our render reveals that it most definitely is the case. You can see we have a very nice subtle depth-of-field effect working on our table. Of course, if this is a little too subtle for us, we can increase the depth-of-field effect, if go back into our Physical Camera controls. We could lower our F Number; of course that would mean we would need to compensate by altering our Exposure controls once again.
There is another option for increasing the strength of our depth-of-field effect, and this is to work with the Override Focal Length option. This will allow us to override SketchUp's lens value and enter one of our own. Now remember, at this moment in time, we are working with a 65 mm lens in the SketchUp viewport, but we can alter that by changing this to something really strong, like 120 mm. Now of course, typically speaking, changing the focal length of our camera would completely change the framing of our shot.
But with our Override Focal Distance option enabled, this actually doesn't happen. We get the depth-of-field effect increased as if we had to 120 mm lens on our camera, but the framing of our shot will not alter. In fact, let's take a render and show you that that is indeed the case. Well, clearly, we have dramatically increased the strength of our depth-of-field effect, so much so that our table is becoming almost invisible in parts.
And you can also see that we have not changed the framing of our shot at all, which can be really, really handy in certain instances. Again, it is not physical behavior, but certainly it is an override that can help us out in many, many cases. So, depth of field with the V-Ray Physical Camera works exactly as per real-world cameras. The only difference really is that we have to deliberately enable the effect in our V-Ray Physical Camera to get it working, and we do have a couple of non-physical overrides that can help us out, that can give us some very fine artistic control over our depth- of-field effects.
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