petrochemist
TPF junkie!
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- Mar 9, 2014
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Whilst this is true, lenses show more aberations when fully open than when closed down a stop or two.For all practical photography purpose and DoF, all stars, including our sun, are at infinity.
Consequently there is no need to use a middle or smaller aperture to deepen the DoF.
By the same token a wide angle focal length like 20 mm has pretty deep DoF even when using a large aperture .
With longer lenses it can also be difficult to get the focus spot on infinity so the increased DOF can be useful to correct for slight misfocusing.
f/8 does seem excessively small for a 20mm focal length though.