Model Railroad System  2.2.1
Overall User Manaual
Camera Programs Reference

AnyDistance and Closest compute the view angle in both real and scale units. It also computes the effective scale of the imaging plane, such as the size of a 35mm slide, which might be used as a transparency for model window panes or locomotive number boards.

Both programs work the same. The only difference is that Closest uses the closest effective focus of the lens and AnyDistance uses a user specified focus distance. Given the input parameters, the distance, the lens, the scale, and the film size, a diagram is displayed with the dimensions of the view. This diagram can be printed using the Print... menu item under the File menu.

New lenses can be entered with the New menu item under the File menu. The Open... and Save.. menu items can load and save the set of available lenses.

Both programs solve the equation below and display a diagram illustrating the solution. AnyDistance uses a user entered value for $D$ and Closest uses the closest focusing distance for the selected lens.

\begin{equation} W_{view} = (D S) 2 \tan(\frac{\theta}{2}) \end{equation}

Where:

\begin{eqnarray*} W_{view} &=& \mbox{The scale view width.}\\ D &=& \mbox{The distance between the scene and the camera lens.}\\ S &=& \mbox{The model scale factor.}\\ \mbox{and} \\ \theta &=& \mbox{The lens view angle.} \end{eqnarray*}

The main GUI screen of the AnyDistance program is shown below. The Closest program is much the same, except that the distance parameter is omitted.