This ratio is approximate, and breaks down in the macro range of the larger format ( the value of m in the numerator is no longer negligible ) or as distance approaches the hyperfocal distance for the smaller format ( the DOF of the smaller format approaches infinity ).
32.
But he does not invert this to find the " S " corresponding to a given " c " criterion ( i . e . he does not solve for the hyperfocal distance ), nor does he consider focusing at any other distance than infinity.
33.
The "'Depssi "'card ( Depth of field, sunrise, sunset indicator ) is a handy guide / reference card that has two functions; it enables the outdoor photographer to quickly select the hyperfocal distance for different lenses ( or zoom settings ) using various apertures.
34.
Fixed-focus lenses are unable to produce sharp close-ups, or images of objects that are only a fraction of the hyperfocal distance from the camera which, depending on factors including the size of the camera, may be within 2.4 3.7 meters ( 8 12 feet ).
35.
Two commonly used alternative focusing techniques are zone focusing and hyperfocal distance, either to free the photographer from manual-focus; or where autofocus is too slow, or the photographer cannot be sure the focus point will fall where the photographer chooses to place their subject in a quickly changing situation; and which also facilitate shooting " from the hip " i . e . without bringing the camera up to the eye.
36.
I'm not sure what the hyperfocal distance for a typical telescopic sight is, but since 1 ) the sights are very small, 2 ) the distances involved are very large ( otherwise you wouldn't bother with a telescopic sight ) and 3 ) the acceptable amount of blur is quite high ( you don't need to be able to see the object clearly, you just need to be able to see where it is in order to aim at it ), it wouldn't surprise me at all if focusing at infinity worked fine the vast majority of the time .-- talk ) 18 : 40, 5 March 2011 ( UTC)
