¡2 Focusing and Depth of Field
The focusing of wide-angle lenses appears to be relatively non-critical due to their large depth of field.. However, careful focusing is actually necessary to utilize the high imaging quality of this lens to the full.. To ensure maxi- mum brightness of the focusing screen and the best recognition of the ide- al focusing point, the aperture should be opened by pivoting the stopping- down lever toward the shifting knob.. The aperture setting ring therefore remains on the set working aperture so that the aperture can later again be closed to the working aperture quickly using the stopping-down lever directly before the shot without moving the eye from the viewfinder..
Focusing can generally take place before or after the parallel shift as de- sired.. However, if the LED focus display of an autofocus camera is used for manually focusing, focusing must take place in the centered position (i.. e.. with a non-shifted lens) because the AF sensor requires incidence of light approximately parallel to the axis, but the light is obliquely incident on the sensor when the lens is shifted.. The parallel shift which then takes place after the focusing does not influence the set distance..
The f-numbers at both sides of the index mark for distance and aperture indicate the depth of field: If e.. g.. everything from ¡ m to 3 m should be sharp, the distance ring should be set so that the meter figures ¡ and 3 are above the same f-number (here: 8) at both sides of the index mark..
