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What do you mean f/1.8 equivalent? I thought focal lengths were different for different sensor sizes, not apertures.
by carlob 5y ago
What do you mean f/1.8 equivalent? I thought focal lengths were different for different sensor sizes, not apertures.
- bayindirh 5y agothe F number is calculated by f/D where f is the focal length and D is the diameter of entrance pupil. For a F/1.0, 50mm lens, you need a 50mm front element. In Opal's terms, this means their f/D ratio is 1.8. However, it doesn't mean it can capture equal number of photons with a full frame system with a f/1.8 lens, since their sensors' surface area is not equivalent. Another difference will be in DoF. Since the sensor is smaller, there'll be a big crop factor, it'll multiply everything. Hence the resulting DoF will not be anything like a full frame system. In other words, almost everything will be in focus. To add a cherry on top, they're not telling the T number of their lens, which defines how much light actually passes through it. F number and T number can be vastly different, intentionally or unintentionally, due to design parameters and features of a lens.
- numpad0 5y agoFocal distance is 4.81mm. 4.81mm/1.8 = 2.67mm. Don’t worry, there’s no such thing as “equivalent F-stop” and you also don’t have to have front lens element as wide as the aperture.
- AirborneUnicorn 5y agoAs I understand it, a larger sensor size will require longer focal lengths to match an "equivalent" view angle as a smaller sensor. As focal length increases, perceived depth of field becomes more shallow. Which is to say, a lens at f/4 on a 4x5 camera will will be much more shallow than an equivalent angle lens on a smaller film/sensor size.