Aperture

huehnerhose · 2006-02-06T09:04:10+00:00

Hallo! Ich hab mal eine Frage bzgl Blendenangaben. Wenn von Über/unterbelichtung gesprochen wird, dann komme solchen angaben wie "Eine Blende mehr" o.ä. Bei...

huehnerhose

Hello! I have a question about aperture settings. When people talk about over- or underexposure, they often use phrases like ‘one stop more’ or similar. With lenses, you’re supposed to stop down by 1–2 stops for better optical performance. Do these figures refer to ‘aperture steps’ (4, 5.6, 8) or to whole ‘aperture values’ (4, 8, 16)? If I’m right, then “one stop” means halving the aperture opening. That is, stopping down one stop on a lens with a maximum aperture of f/4 would result in f/8. But if I’m now supposed to stop down two stops for optical performance, I’d have to stop down to f/16. So I’m thinking here that they mean “stop steps”, i.e. from f/4 to f/8, which would then only correspond to one “stop”? I’m a bit confused about this topic :) Thanks to anyone who tries to untangle my confusion :P Regards Sebastian

seba

Do these figures refer to "aperture steps" (4, 5.6, 8) or to whole "aperture values" (4, 8, 16)? If I am correct, then "one stop" means halving the aperture opening. The key factor is the amount of light. Doubling the amount of light is achieved either by doubling the aperture opening (area factor: ~1.4 (square root of 2), i.e. 1, 1.4, 2 ...) or by doubling the exposure time (factor 2, i.e. 1/60, 1/30, 1/15 ...). Have a look here , Seba

Gast

Hello Sebastian, The aperture values indicate the diameter of the aperture opening in relation to the focal length. For a lens with a focal length of 50 mm, an aperture of f/1.1 therefore corresponds to an aperture diameter of 50 mm, f/1.4 to 35 mm, f/2 to 25 mm, and so on. However, when the diameter is halved, the aperture area is only a quarter of the original, as the area of a circle is pi*r². This is why the steps from one aperture to the next are by a factor of approximately 1.4, i.e. the square root of 2. For the 50 mm lens: Aperture 1:1 – area approx. 80 cm² Aperture 1:1.4 – area approx. 40 cm² Aperture 1:2 – area approx. 20 cm² In other words, stopping down by one stop means going from 1 to 1.4 or from 4 to 5.6, because this halves the aperture area and thus also the amount of light. You can equate aperture and aperture step here. Does that clear things up? Best regards, Heiko

huehnerhose

Oh, what a load of rubbish... thanks! I was just thinking in terms of ratios like 1:x and not in terms of circular areas... Thanks!