I know when they measure zooms, you see numbers like 10x or 3x or 14x...and I know you see the number of millimeters the lense is...30-200mm, etc...and I know the sensor size (1/3", 2/3", 35mm) has some bearing on the actual image as well.

When looking at cameras like the Red or a 2/3" sensor camera is there anyway to compare how much zoom...how close objects will look at their maximum zoom? Is there a formula to figure this out on my own if the industry doesn't make it easy to compare this?

I'm real curious to how much MORE zoom you can get with real high quality glass on a high end camera compared to the inexpensive cameras like the Sony Z1u or Ex-1. Those have 1/3" and 1/2" sensors, 12x an 14x zoom ratio, 30-360mm roughly lenses.

How would this compare to say a Scarlet or 2/3" sensor with a 42x from Canon and a 800mm lense? Would this appear twice as close at max zoom or 3 times closer?

How to figure that out?