Wednesday, 1 January 2003

Exposure Control

The difference between a ‘good’ and ‘fine’ print
is in the retention of detail in the deepest shadows and highest highlights.
Once the basic exposure for a print has been determined it is usual to apply
several steps of dodge or burn in order to balance the detail in the shadows
and highlights. This can become a most compulsive obsession in the darkroom.
It is not unusual to execute a dozen or more dodge and burn steps for a given

Each step is applied for a given time, and if the print
is to be reproduced all those times must be recorded, and each individually
recalculated if any of the exposure conditions change. One reason exposure may
change is if the lens aperture is adjusted to give longer exposure times, so
that the dodge and burns are more manageable.

Longer dodge and burn times are easier to manage because
there is usually a short (1 second say) ‘error’ when synchronising the
position of the mask with the operation of the enlarger. This error has a
smaller impact when the dodge or burn time is longer.

So if you decide to perform a
dodge for five seconds you may well stop the aperture down to give a ten
second dodge – remembering at the same time to double the base exposure.
Sounds simple enough, but with up to a dozen such steps the calculations
interfere with the artistic thought processes that are on-going at the same

The whole story is similarly
complicated if the enlargement factor is changed, or the contrast filtration(s),
or the paper batch. Considering Ansel Adams’ ‘how to’ series,

is useful to think of a dodging or burning-in time as a
of the total exposure. We can become quite proficient at
estimating the effect of dodging or burning an area for, say, 20
percent of the total exposure time.’

Adams, A (1995), The Print, Vol III The
Ansel Adams Photography Series, (pp 102). Little, Brown & Company

In Adam’s ‘Clearing Winter Storm’ example his ten
dodge and burn steps use only six different times. There are two –2s dodges,
one 1s, one 2s, one 3s, one 9s, and three 10s burns, with a 2 to 4s
corner burn. The 9s burn is performed in three 3s sweeps and two of the 10s
burns are performed through a hole rather than by a simple mask (see fig. 1).
The image of Adams’ hands literally dancing in the enlarger light stream through all these steps
is compelling and helps to illustrate his philosophy of the print as

Figure 1 Burn Map for the Ansel Adams example
(showing duration and types of dodge/burn steps)

The performance of the print, the subjective decisions
about exactly where to place the mask, by how far to overlap the surrounding
area, and exactly when to end the operation, are the factors that should be
consuming the attention of the photographer. It is this process that makes each
print unique, and it is uniqueness that is the wet darkroom’s unassailable
strength over the digital workflow.

It is worth then creating a method of work that simplifies
the numbers, mental calculations, and feats of memory required in the print
performance, so that the creative mind is at greatest liberty to realise that

Using percentages helps in this respect, especially when
the exposure must change, but there are still many different actual numbers to
remember, the duration of each dodge or burn step. Fortunately the process can
be further simplified.

First of all, in practice there is a minimum dodge-or-burn
time that produces an effective result. This will vary between different
material combinations but there are only a relatively few such combinations in
use by any given photographer. The minimum effective dodge or burn time for a
given paper/developer combination can be determined through experience. I
generally constrain dodge and burn times to a minimum of 5% of the base exposure
time with Ilford Multigrade IV™ RC Gloss developed in Multigrade Developer™.

Secondly, the precise dodge and burn time is not decided
rationally and absolutely whilst reviewing the proof print but rather is part of
the subjective performance of the print, within bounds. What this means is that
instead of thinking about three separate burns with three separate burn times of
1s, 2s, and 3s we can think of three separate burns that are around 2s. The
actual difference between the burns is decided on-the-fly during the exposures.
All three burn steps are applied with the enlarger set to 2s. The first burn can
then be given ‘about half’ the 2s exposure time. The second burn is given
‘most’ of the 2s exposure time. The third burn is definitely given one full
2s burn followed by ‘about half’ of this standard 2s exposure time.

The above scenario reduces the number of times that have to
be considered and the need to constantly change the enlarger timer setting
(reducing chance for error).

When creating a ‘fine’ print the subjective terms
‘about half’ and ‘most’ are counter-intuitive. It seems that such
approximations lack accuracy and so cannot give rise to a controlled final

The subjective approach does however work. The absolute
‘inaccuracy’ is controlled by the size of the standard burn or dodge step
chosen. The 3s exposure above will be given at least 2s and no more than 4s, and
so will not be that inaccurate.

Also, it is unlikely that a difference between, say, 3.9s
and 4s would yield a perceivable difference in the print. The dodge and burn
steps need not be applied with any accuracy greater than, say, 5% of the base
exposure time. For a 10s base exposure the effect of a 3s burn can be achieved
anywhere between 2.5 and 3.5s.

Most especially, the subjective approach works because the
precise, final decision of how much of the second 2s exposure we give to the
third burn is taken as the exposure is being applied. The photographer is not
concerned with resetting the enlarger timer, only that the third burn should
receive one full standard exposure and one partial standard exposure. During the
partial standard exposure the thought processes are entirely concerned with what
was perceived from the proof print, and the subjective effect desired, and how
well the operation has been carried out so far – in real time.

This constrained-subjective method is further supported
when one considers that there is no such thing as ‘the final print’. The
printing of a given negative will always change as it is informed by the
development of the photographers’ style. A constrained-subjective approach
creates a workflow where the print is given the opportunity to reveal something
new that has not been previously, consciously considered – by its very
subjective nature.

Figure 2
Fixed Increment example burn map (note
regularity in time & subjective language)

The ‘standard exposure time’ for dodge and burn steps
is determined on a per-print basis and is a function of the base exposure time
and the minimum effective dodge or burn time. Performing all dodge and burn
steps with a single enlarger timer setting (or multiples thereof), instead of
perhaps a dozen different timer settings, greatly simplifies the printing

Once the proof print has been evaluated a decision is taken
regarding the relationship between the different dodge and burn amounts required
and the responsiveness (i.e. sensitometry) of the paper/developer combination.
For a base exposure of 60s with a 50% sky-burn and a 25% central dodge, for
example, the enlarger timer would be set to 15s. The base exposure would be
achieved with 4 ‘standard exposures’ for the print, during one of which the
dodge would be applied. Two further ‘standard exposures’ would then be made
to burn the sky area. The entire print is made with only one timer setting.

The principal is also useful for split-grade printing. If
the entire print may be given 80% at grade 5 followed by 20% at grade 0 the
timer would be set to 20% of the base exposure and applied 4 times at grade 5
and once at grade 0. Eliminating the need to reset the timer reduces the
opportunity for error.

Such a method should not be applied thoughtlessly or
slavishly. As the number of ‘standard exposures’ required for a dodge or
burn step increases the chance of miss counting also increases, so eventually
the method becomes more complex than continually adjusting the timer. The
important principal is to establish some method that aids and simplifies
repeatability within the confines of the print’s sensitometry and the
photographer’s creative freedom. As a worked example the figure below shows
the dodge and burn map for the photograph at the head of this article.

Because of the extreme latitude I originally found the
exposure for the main window through one test strip and the left-hand wall
through a second. These suggested 45s for the window and 9s for the wall. I
decided to work at a fixed 9s exposure increment, with one increment for the
base exposure. A series of additional 9s fixed increment exposures were applied
as per the map.

The base exposure need not have been a single increment. In
this case the smallest burns were 100% of the base exposure. Had they been 20 or
50 percent then the base exposure may have been made from 5 or 2 increments,
respectively. Also if I had needed to dodge an area I may have arranged the
fixed increment in order to provide an entire exposure step for the burn
operation and one step with no planned dodge or burn. Planning to have a dodge
and burn free single exposure increment creates space for last minute
adjustments. Usually applied as the final exposure increment this allows for
last minute tweaks based upon the printer’s immediate reaction to the print as
is has just been performed.

The fixed increment exposure method is much simpler in
practice than in theory. By design the method is imprecise. The purpose is to
give rigour to the numeric process of exposure so that there is a well-defined
framework for the creative process. This means that some liberty can be taken in
setting the fixed increment value. If the numbers aren’t as convenient as in
the example they can be tweaked. Each increment will be used in an ‘about’
way. The base exposure however should be an exact number of fixed increment

The benefit of the fixed increment exposure method is that
during printing we need only count exposure increments whilst concentrating on
the precise nature of the dodge or burn. In the example, the +4 burn of the main
window illustrates this. How far into the image this burn extends, and for how
long the burn maintains its maximum reach, is the on going subjective thought
process during the burn operation. The outcome affects the floor in a major way.
The feel of the image can be entirely controlled by the amount of burning
to this floor area.