FS7: Speedbooster calculations, am I right with this?

A

alohype

Veteran
Hi!

Am I calculating it correctly?
Will
12mm 2.0 Super35 e-mount lens get exactly same FOV and light gathering as
17.5mm 2.8 Full Frame lens on a SpeedBooster?

My calculations are like this: 12mm*1.6 (super35 crop)= 19.2
17.5 * 1.1 (crop with SB)= 19.25 (plus additional stop of light)

Thanks for help!
 
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You are right except it is as simple as: 12mm divided by 0.71 (speed booster reduction factor) = 16.9mm. Or if you are going other way 16.9mm x 0.71 = 11.999mm.

Since both of the lenses' FOV in question is for when they are used on S35 sensor, therefore whether they are originally Full Frame or Medium Format or any other format lenses is irrelevant (of course as long as their image circle is big enough for Speed Booster use to begin with, here minimum being Full Frame ), no need to include additional crop factors in this equation.
 
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You want to get the same image as an 18mm f/2.8 lens on a FF camera?

You need a s35 12mm f/2 lens on the FS7 s35 sensor.

You can get it by two ways,

-add a SB to a FF 18mm f/2.8, and turns into a s35 12mm f/2 lens.
-Get a native s35 12mm f/2 lens.

The speedbooater calculations are simple. Just x0.71.
 
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