THE NUMBER ONE PROBLEM WITH
B & W PHOTOGRAPHY.
There is only one correct exposure for a particular scene.
While there may be several different exposures possible in
order to " place" a particular area of the scene in a tone or
zone, there is only one correct exposure.
That particular exposure is obtained only when the exact,
true ASA or film speed has been used.
( You'll never know if you are really using it unless you test ! )
Manufacturer's suggested film speeds must be adjusted for
each and every:
camera , lens , meter , and development combination.
in order for (zone system) controls to operate.
Your personal film speed may easily be 1 to 2 stops (tones or
zones) off. So, that scene with " 400 " speed film may get shot
in reality at 100 or 800 speed resulting in a loss of detail in the
shadows or highlights.
Once your personal film speed and normal development time
is determined predictable photographs will follow.
This will produce minimum density negatives ,with less grain ,
that allow more enlargement and maximize the number of
zones or tones you can capture from a scene.
The ( zone or tone ) film speed tests are calibrated
( or referenced ) at zone 1, which is almost black
in the print to produce this minimum density value.
The classic zone 1 density value is 0.10 above film
base plus fog. Film base plus fog being developed ,
unexposed film and assigned a value of zone 0.
In practice however, a value of 0.12 above film base plus
fog is widely accepted. The theory being, that like everything
else, today's paper isn't what it used to be.
Follow these " simple " instructions and we will determine
your personal film speed with an electronic densitometer.
E-mail us with your questions.
Required Materials:
1 roll of film. 18 % neutral test card, or even toned grey subject
if you can recognize zone 5 ( not very accurate ).
The Kodak 18% neutral test card is highly recommended
(if you don't have one already ). That shade of grey reflects
a Zone 5 exposure and is very useful in metering scenes.
Of course your photo of a grey card will
only produce a zone 5 print when you
have calibrated your equipment and
processing. This is the whole point of
these exercises!!!!
2 (two) 4800 degree K (daylight) photo floods.
( also highly recommended) or unchanging daylight .
SEE USEFUL PRODUCTS ( Photo floods under $ 25.)
Photo floods are relatively inexpensive and very useful in
portrait or product photography. In this exercise they are
also very valuable as they allow you to light the grey card
much more powerfully and consistently than daylight.
Very importantly this light intensity allows you to use
a minimum number of shutter speeds with the full
range of apertures which is inherently more accurate.
Adjust the light intensity until you are able to use a
shutter speed that you will often use in general
photography such as 1/125. As a result you will be
calibrated at a commonly used shutter speed.
Meter and photograph the gray card.
Avoid casting a shadow onto the card.
Avoid any reflection from the slightly glossy surface.
Focus on infinity. Use the test table page to record
you settings.
Expose frames 1-3 with the lens cap on.
Set light meter at twice the recommended asa.
The meter will register a zone 5 exposure
(that's what light meters do ).
Reduce exposure 4 (four) F numbers to place it on zone 1.
Expose frame #4 to this zone 1 exposure.
Change asa to 1.5 times that recommended.
Meter reading will yield a zone 5 value.
(that's what light meters do!)
Reduce exposure 4 (four) F numbers.
Expose frame 5 to the zone 1 exposure.
Expose frame 6 to the zone 1 value for the manufacturer's recommended asa.
Expose frame 7 to the zone 1 value for 0.75 times the recommended asa.
Expose frame 8 to the zone 1 value for 0.5 times the recommended asa.
Expose frame 9 to the zone 1 value for 0.25 times the recommended asa.
Expose the remaining frames to zone 5.
Use these frames to check your shutter speeds and apertures
by varying them to produce the same amount of exposure.
Any significant difference in the density of these frames
indicates a problem with your shutter or lens aperture.
Develop the film normally.
Your processing techniques , from chemical mixing to film
rinsing must be very consistent from roll to roll for tests and
zone system controls to operate.
This cannot be stressed enough. If you have not developed a
consistent dark room technique and temperature control,
please do not bother with this testing. With just a few
degrees of temperature variation from one roll to
another we will unable to draw any meaningful
conclusions from your data!
Record your settings on the
FILM SPEED TEST ASA SETTINGS AND RESULTS SPREADSHEET.
Mail the film to us with a copy of the table.
Include payment of $ 10 or use the Paypal link provided.
The table can be submitted via e-mail (download file,
update info, e-mail. and therefore returned via e-mail.
However, if you want the film back we will mail the
record with it.
Find the frame with the density 0.12 higher than a zone 0
(lens cap on). The asa listed under this frame is your asa
for that film, camera, lens, meter.
