Practical difference between Focal Width and Focal Distance?

Testing6790

Hi all,

I was playing around with getting a wider shot yesterday and found that these two options do roughly the same thing. Narrow or widen the shot. I tried rendering the scene by adjusting one of each and checking for differences and I didn't really see one.

What is the difference?

Richard Haseltine

Do you mean Frame Width? That has its most noticeable effect when you have a very wide aspect to your camera - try setting the aspect ratio to 10:1 and then experiment with the Frame Width setting, noticing how the behaviour of the perspective changes. This is a new feature added as people were having problems getting acceptable results with widescreen renders.

glaseye

Erm, I take it you're talking about frame width and focal length; focal distance is used for the distance between the object and the camera lens (for use with depth of field)
Frame width would be the size of the negative on a rol of film (remember those ) most commonly 36x24mm, hence the default value of 36 (nowadays that would be sensor size )

The focal length would be the convergence point for the camera lens, usually the 'base' lens would be about 50-55mm for the above mentioned camera (shorter for most digital cameras)

So, a wider frame widht with the same focal length gives a wider view (Field of view), In rendering it makes the biggest difference when you use depth of field. longer focal length gives a smaller 'depth area' were the image will be in focus.

LoL, Richard beat me to it (didn't get a notice as I would in the old forum....)