Pentax 6x7 Manual page 25

Magnifications and Exposure Factors
A reading of 3.2 on the magnification scale
indicates that a magnification of 1/ 3 .2 will be
obtained . When metering with an independent
light meter, exposure must be increased as
indicated in the chart below. Exposure com-
pensation is not required as such when using
the accessory TTL metering Pentaprism Finder.
However, film reciprocity varies with different
f ilms, and required compensation should be
made accordingly in compliance with the
manufacturer 's guide, with or without TTL
metering.
In close -up work, the depth of,field is gener-
ally shallow. Best results can be obtained by
preselecting the lens aperture. However, as
inbetween shutter speeds are not available, the
aperture should be opened up an additional
1/ 2
stop at the
1.5
magnification setting . At
the " 2 " setting, lower the shutter speed 1
step, or open up the aperture a full extra stop .
SMC MACRO TAKUMAR EXPOSURE FACTORS
MAGNIFICATION
E XPOSURE FACTOR
Why Exposure Compensation is Necessary
With close-ups, the volume of light reaching
the film plane decreases by half in porportion
to magnification increase. TTL meters over-
come this problem by measuring the total
amount of light entering the lens. However,
unless the meter is located behind the lens,
this loss requires compensation .
Irregularities in Coior Film
With time exposures in excess of 1 sec.
using color film , certainirregularites in film
response often lead to undereposure ; thus,
exposure times often have to be increased at
slow speeds . Moreover, with most reverse
color films, color reproduction characteristics
change with exposures longer than 1/ 10
second . However, irregularities can be
avoided by using CC filters
. Refer to guides
published by the respective manufacturer for
exact data concerning color reproduction
characteristics and required compensation
for the film in use .
23