# Zoom (ProShow)

INTRODUCTION
This is an introduction to changing a ProShow Producer layer’s zoom using a modifier. When the zoom value of a ProShow layer is entered as a decimal number, ProShow rounds the displayed value up or down in value. If the decimal value is 0.5 or larger, the displayed value is rounded up. If the decimal value is less than 0.5, it is rounded down. Unfortunately, that can provide an erroneous indication of what the layer’s actual zoom setting really is (see Rotate/Tilt/Zoom Values). However, ProShow truncates the displayed zoom value as a whole number. The actual decimal value entered is retained.

One way to get around the rounding problem is to change the layer’s zoom with a modifier. It is not a direct change in layer size but, it works. You can always work out what the layer’s actual zoom is because you know the layer’s set value of zoom and the modifier value. Together, they tell you the final zoom setting for the layer.

However, this is not the only reason to use a zoom modifier to change the size of a layer. We may use a modifier to force an aspect change to the layer. For example, converting a 16:9 layer to a 3:2 aspect. But, the reason to do this can be almost anything.

THE ZOOM MODIFIER
A zoom modifier is simply a value that represents the percent of change of the layer’s existing zoom setting. So, a layer with a zoom setting of 100 and a modifier of 10 gives the layer a final zoom setting of 110 when the slide is played. The simplest method of changing a layer’s zoom with a modifier is to simply add a Constant Value action.

When a layer’s zoom value is changed using a constant value modifier, the change is the amount of layer’s existing zoom by a percent of that zoom value.

Let’s say we know the layer’s existing zoom, Zs (start Zoom), and we know what value of zoom we want the layer to have via a modifier, Ze (end Zoom). To calculate the modifier, we use the following relationship:

M = 100 * (Ze – Zs)/Zs   (Eqn 1)

So, if the Start Zoom (Zs) is 50 and the End Zoom (Ze) is 60, the Modifier (M) is 30.

If we knew the Modifier and the Starting value of zoom, we rearrange Eqn 1 to get the following relationship:

Ze = Zs*(1 + (M/100))  (Eqn 2)

ZOOM MODIFIER RELATIONSHIPS
These are the basic relationships. Equation 1 provides the basis for calculation the modifier value. But, since the values of Ze, Zs, and M are related, knowing any two lets you find the value of the missing value. But, there’s more to this zoom modifier than meets the eye. It turns out that these relationships work in ProShow as given only if the two axes have the exact same zoom value. If they are unequal, the value of the opposite axis will have an effect on the calculation of the modifier for the other axis. The following relationships apply:

Mx = (100*(Xe-Xs)/Xs) * If (Xs < Ys, (Xs/Ys), else 1)
My = (100*(Ye-Ys)/Ys) * If (Xs≤ Ys, 1, else (Ys/Xs))

So, if our Start Zoom-X is 50, the Start Zoom-Y is 40, the desired End Zoom-X and Zoom-Y are both 65, the result would be Mx=30 and My=50.

Mx = (100(65-50)/50)1 = 30
My = (100(65-40)/40)40/50 = 50

CALCULATE MODIFIER FOR Xs = Ys:
Mx = (100*(Xe-Xs)/Xs)
My = (100*(Ye-Ys)/Ys)

• CALCULATE MODIFIER FOR Xs < Ys:
Mx = (100*(Xe-Xs)/Xs) * Xs/Ys
My = (100*(Ye-Ys)/Ys)

• CALCULATE MODIFIER FOR Xs > Ys:
Mx = (100*(Xe-Xs)/Xs)
My = (100*(Ye-Ys)/Ys)*Ys/Xs

These modifiers are particularly useful for creating thin outlines around a layer (using a layer with the same starting size behind it). Refer to Simple Frames: User Created Outlines to see how this technique applied there, manually. You might want to increase the layer’s size layer by something like 0.25%. While you can type change in zoom directly into the zoom-x and/or zoom-y box, the value that ultimately is shown is a decimal number. That is, if you type in 30.5, ProShow will change it to show only 31. If you have edit the zoom value at a later date, you may have no idea what decimal value is actually being used. If, instead, you had added a constant value modifier, you would have a way of finding the exact zoom value used to create the outline layer.  To change a layer’s given zoom from 30 to 30.5, a constant value modifier of 1.67 is what you would add to the zoom box.

ADDING A ZOOM MODIFIER TO A LAYER.
Right click over the zoom box, select Add Modifier. The Constant Amount radial button is selected by default. Enter a value into the Constant Amount box (1.67 for the example above). In the Actions section, notice the value you just entered (for the example above, that show an action line of:  (+) 1.67.