# What is the Perspective Distance value?

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I use Perspective Distance all the time in Vectorworks to change the amount of perspective in my view. I understand its function, but it just occurred to me that I don't understand what the value actually is. Does it relate to something in a physical camera?

For RW Cameras there's the "Field of View" parameter which alters the exact same thing, but in that case it's easier to understand what the number is referencing.

Just curious 🙂

The distance is the distance between the center of projection and the view plane, if that helps.  What you see will depend on layer scale and crop rect, if that is on.

I'm once again curious what the "Perspective Distance" value actually relates to in real life. What is the 'view plane' referred to above (in Vectorworks I mean)? If the view plane were visible or measurable that answer would make more sense to me. Also, I'm not sure what layer scale has to do with it. I'd be thankful for additional explanation there.

I realize this parameter changes the amount of perspective, but is it referring to a measurable distance? Or is it a scale factor of some sort? Or is it an arbitrary number? (that's a valid answer).

With some playing around, it seems that there's a relationship of 1:1.111 between the Perspective Distance and the width of the camera view at that distance. For example, if I set the Perspective Distance to 10, then 10" away from my camera's origin the width happens to be 11.111" wide. This ratio seems to hold true for any distance and also in other units, though I'm not sure what conclusion can be drawn from this, haha.

I'm down the rabbit hole a bit, and at the end of the day it's just curiosity and not crucial. Currently when students ask what that number is I simply say it's arbitrary and there's no reasoning behind it. Hopefully I'm wrong.

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