The Vray physical camera differs from the 3ds Max standard camera in that it has adjustable settings for ISO, shutter speed and f-stop. These settings can aid in the lighting and overall look of the scene. At first, the Vray Physical Camera settings can appear daunting as there are many settings you can tweak but for the average user who is not an expert in photography, impressive results by changing the following settings can be seen.
Film gate and focal length
It really depends on where your camera is placed within the scene, and what you wish to have in view. You may find yourself restricted by walls and other objects, but you can easily overcome this using camera clipping or setting the object that is causing the obstruction to not be visible to the camera in the object properties. As a base point I would set your focal length to 45mm and your film gate anywhere between 40mm and 60mm.
If your goal is to replicate a real camera then you can find out the specification by doing some internet searching. You will find information on all the settings within the Vray physical camera. I recommend following this guide which goes through the necessary settings and functions of a Canon PowerShot, You can easily adapt this work flow to any real camera.
Determines the length of time the camera catches the light, the slower the shutter speed, the brighter the image. Motion blur can also be affected by this because a short shutter produces less blur due to a smaller length of time being captured. For interior visualisation a good starting speed is 60 and depending on your intentions with the f-stop you may have to use a slower shutter speed.
This controls the size of the camera aperture (the hole that lets the light pass through). A smaller number means a larger hole which will make the object closest to the camera sharper and the background blurred. This is a powerful effect when setting up close up shots and at the same time making other objects appear out of focus which is called depth of field (DOF). By decreasing the f-stop you are brightening the image and you may experience over brightness or a burnt out image. To compensate for this the shutter speed will need to be shortened.
A good f-stop number to start at when focusing on an object closest to you is 2 or 2.8. I use the standard f-number series when choosing the f-stop as these values are exactly twice or one-half the amount of light of the neighbouring f-number. More information on the f-number series can be found here.
For standard camera views without DOF, change the F-stop to 4 or 8 depending on the lighting within your scene. When changing the f-stop, you either double or halve the amount of light that passes through, therefore you need to either double or halve the shutter speed to keep your scene from being under or over exposed.
All other settings can remain their default values. You would only adjust the ISO value if a desired DOF effect has resulted in an under or over exposed image. The only way to control exposure is with the ISO as this has no effect on DOF whereas F-stop and shutter speed do.
If you have any questions about this post feel free to leave a comment and I will do my best to answer as soon as possible.