Can you solve this equation?

Started 1 month ago | Questions thread
A Marcus Forum Member • Posts: 50
Re: Can you solve this equation?

A 0.71 speed booster alters the focal length of the lens it is mated with. Thus the 35mm focal length lens becomes 35 x 0.71 = 21.81mm let’s say the final focal length is about 22mm. The original maximum f-number of the 35mm lens is f/1.8. The working diameter of the aperture is about 35 ÷ 1.8 = 19.4mm. With the speed booster in place the math to find the revised working f-number is 22 ÷ 19.4 = 1.1 written as f/1.1. This is a speed gain is about + ½ f-stop.

A 22mm lens, mounted on a compact digital 1.6x crop factor, delivers an angle of view of about 54° camera held horizontal. If you mount a 22 x 1.6 = 35mm on a full frame camera, this lash-up will deliver a 54° horizontal angle of view.

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