The depth of field scale shows clearly how much of the subject will be sharp at any given distance and aperture. The
figure opposite the triangular index mark is the focused distance, in this case 25 ft. The figures to either side of the
index mark represent aperture settings. For instance, at f5.6 the depth extends from about 13 ft. to infinity. At
nearer subject distances the depth of field is reduced: thus at 8 ft. it only extends from about 6 to 11 ft.
The Retinette II and IIB models have an automatic depth of field indicator, consisting of two pointers coupled to the
aperture setting. At any aperture, therefore, the pointers directly indicate the depth of field available, and they
move outwards at small apertures and inwards at larger ones.
Zone Focusing
The Retinette user will often aim at snapshots by seizing a situation as he comes across it without many
preliminaries, certainly without setting up a tripod, and mostly with the least possible loss of time. To attain this he
will not only have to know his camera inside out but he also needs a ready-for-shooting lens setting which will yield
a sharp picture every time. Such settings are the focusing zones. Here the relatively short focal length of the
Retinette lenses scores; it gives the advantage of a comparatively large depth of satisfactory definition even at the
more open apertures.
From what was said about depth of field on the previous pages, it is clear that the stop is used to regulate the
definition of the picture in depth (both towards foreground and background) from the point at which the lens is
actually focused. Now, the idea could occur to the beginner to try to use the smallest stop every time to make sure
of sharp pictures. That, however, would mean that in the majority of cases he would not arrive at a practicable
exposure time because, while it is true that the smaller the stop the greater the depth of field, it is also true that the
smaller the stop the longer the exposure time.
In consequence, the best zone focusing is the compromise between a well-selected medium stop and a suitable
distance setting, yielding a fairly extensive zone of definition and still allowing for a reasonably short exposure.
The more frequently used zone focusing settings are set out in the zone focusing table on page 43, and it may be
found useful to copy them out on a piece of paper which can be fixed in the top flap of the camera case for ready
reference.
The Depth of Field Tables
These tables have been included in this book, in spite of the fact that the Retinettes are fitted with a depth of field
calculator, in order to supply perfectly accurate figures which cannot be obtained with the calculator, the distance
scale not being calibrated in sufficient detail.
The tables are computed on the assumption that the circle of confusion is of 1/20 mm. diameter. The figures on the
left of the table relate to the setting of the lens stop. The bold (middle) figures in each group indicate the distance