Extended User Manual – Irix 15 mm f/2.4
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DEPTH OF FIELD SCALE
ExAMPLE NO 1
In this example, the lens is focused on the eighth
key from the font of the image. The lens aperture
is at its maximum setting of 2.4.
You can see in the image that only the neighboring
keys are in sharp focus at this aperture setting.
The term for this effect is “shallow depth of field”.
As this demonstrates, it would be virtually impos
-
sible to provide legible marks on the DoF scale for
this aperture setting. DoF scales are only useful for
a smaller aperture setting (higher f/number).
In the case of your Irix 15 mm lens, the lowest
number represents f/8.
