The DARKROOM COOKBOOK, Third Edition

38 THE DARKROOM COOKBOOK
Through agitation exhausted developer in areas of high density is replaced with fresh developer,
which continues to develop the highlights, increasing the contrast.
The third, increased sharpness is the result of adjacency effects that occur at the boundaries
of image detail. One of several adjacency effects is the Eberhard effect, which increases
fi ne-line detail in the negative, essential to maintaining quality in prints greater than approximately
10� enlargement. Adjacency effects only occur when the negative is allowed to stand
without agitation for at least 50 seconds. This allows naturally occurring convection currents
to move the developer across areas of high and low density.
There are four methods of agitation: Intermittent, minimal, continuous, and stand development
which will be discussed in its own section below. In order to obtain negatives with the
highest degree of edge sharpness and contrast of fi ne detail, intermittent, minimal, or stand
development must be used. Continuous agitation should be avoided.
Intermittent Agitation To take full advantage of adjacency effects to achieve a high degree of sharpness,
agitate continuously for the fi rst 50 to 60 seconds to prevent chemical defects and then
for 10 seconds every minute thereafter.
Minimal Agitation You can gain additional sharpness by using minimal agitation. This is accomplished
by adding 50% to your normal development time and agitating continuously for the
fi rst 50 to 60 seconds and then for 10 seconds every 3 minutes.
Continuous Agitation This method is especially popular among those using JOBO rotary processors.
The fi lm is agitated non-stop for the full time of development. The direction of agitation
should be varied to avoid streaks or patterns on the fi lm. Development time should be
reduced by 20%.
The difference between intermittent, minimal, and continuous agitation will only be
apparent with enlargements greater than approximately 10�. If you never intend to make
greater than 10� enlargements, it is not as important which agitation method you use.
A 35 mm negative enlarged 10� will be approximately 8 � 14 inches. A 4 � 5 inch negative
enlarged 10� would be approximately 40 � 50 inches. In other words, those developing
4 � 5 inches or larger negatives usually will not need to concern themselves with the difference
as most photographers rarely if ever print as large as 40 � 50 inches. However, those
using 35 mm or 120 fi lm should use intermittent agitation unless they may someday wish to
make 20 � 24 inch prints (20� enlargement), in which case they should consider using minimal
agitation or stand development.
Shorter Agitation Intervals Before adjacency effects were thoroughly researched and understood a
number of fi lm makers, chief among them Agfa, recommended agitation every 30 seconds.
Today, if a formula requires a more frequent agitation cycle than once per minute you
should consider the reason. If the reason is to prevent staining or some other form of negative
defect, I highly recommend not using the formula. There are too many excellent formulas
to choose from without chancing damage to your negatives with a poorly formulated developer
that might damage your fi lm if you do not agitate in a proscribed manner. One agitation