VRay Camera Film Gate

[chriswatt]

I am wondering what is the real use of the film gate in VRay?

 

I have been trying to work it out all week and I really can't find the correct use for it.

 

I spent half of today rendering a VRay Cam with 36mm full frame focal lengths against its 50mm medium format equivalent and there is absolutely no different in the renders.

 

I had a bit of trouble matching the field of view with the the different film gates but settled on the equation for 50mm MF Focal length = (36mm lens size – 10%) x 1.5 or there abouts.

 

The distortion is absolutely the same between the renders. So why is it there?

 

I have searched high and low on the internet for the answer but there is not much information on it. I know in the real world Medium Format has less distortion than Full Frame but it does not seem to translate into VRay the same.

[Chris MacDonald]

I use it every time I do a photomontage. It saves having to work out crop factors for different lenses mounted on different camera bodies/sensor sizes.

 

It's just plain useful.

[chriswatt]

Ahh now I see when it is useful. Thankyou.

[Stephen Thomas]

Also the distortion thing is a bit of a red herring. Perspective is dependent on the distance from the camera to the subject. Whether you change film gate (sensor size) or lens angle, these are just alternative methods of adjusting the FOV. The distortion with wide angle lenses occurs because you move closer to your subject in order to fill the frame, so objects out to the side seem stretched.

 

The reason you don't see this effect with medium format cameras is that they generally don't make MF lenses with such a wide angle of view. Another feature of a larger film gate which you can see the effect of in 3dsmax is that depth of field will be shallower with MF when using same f-stop compared to 35mm camera.

[chriswatt]

Thanks stephen, it is great to know it affects the DOF as it would with a real MF camera. Thankyou for the answers guys, I appreciate it