Originally posted by Digitalis Actually, the f/stops between f/4.0 and f/5.6 is f/4.0,f/4.3, f/4.5, f/4.8 f/5.0, f/5.6, But why stop there? To be realistic 1/3rd stop increments are deliver an acceptable amount of precision for exposure control especially when you take into account the Dynamic range of current digital sensors. The only situation where really high precision lens transmission and aperture control was needed was in cinematography, where older film stocks didn't have much DR (4 stops or so) and a 1/8th of a stop variation in exposure could ruin an entire shoot.
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But what I was getting at was I think the lens (and camera) manufacturers use 3.5 and 4.5 when they mean half stops, not 1/3. I have my camera set to move in 1/2 stops, yet as I adjust the aperture it goes 2.8, 3.5, 4, 4.5, 5.6. Why doesn't it go 2.8, 3.4, 4, 4.8, 5.6? The next half stop after 5.6 shows correctly as 6.7