|
by Mark
Thellmann, InLiquid artist
Part V: Obtaining the Proper Photographic Exposure
Kodak makes what is called a gray card, as an
aid to perfect exposures, but I have always found this term misleading.
This card just happens to have been printed
a neutral gray color, but more importantly it is a surface which
reflects exactly 18% of the light which strikes it. Many other
colors can do this if they are of like density, not just the color
gray. This 18% is a magic percentage, because it is what all light
metering devices are calibrated to in order to obtain the perfect
exposure for the film you are shooting (providing you remembered
to set the ISO number correctly, if your camera requires you to
do this manually.)
Most of the time, what you are photographing
in nature is reflecting light at this 18% value, but when photographing
artwork, unless we are aware of this 18% value, we may get the
wrong exposure. For instance, if you are photographing a painting
with dark tones, the meter will measure the light reflecting at
18% (that's all it knows how to do), but the painting is reflecting
light at maybe only 9% (its tones are dark and dark means more
light is being absorbed than reflected), so the slide is going
to come out overexposed one stop (9 is half of 18) and that means
the slide will be twice as bright as it should be, leading to
loss of detail, tonality, etc. You will be heard throughout the
processing lab exclaiming, I've lost my detail... my tonality!
Exactly the opposite happens with a painting which incorporates
a lot of light, airy, soft pastels. This time you will say, I've
lost my light, airy pastels. This is too dark. It's blocked up!'
So, how do we acquire the correct exposure?
Three possible ways that I know of... 1) Take a TTL (through the
lens) meter reading with your camera. If what you are photographing
is reflecting light at 18%, your exposure should be right on (providing
your camera is working correctly and the lab doesn't process your
film in exhausted chemistry.) If you suspect otherwise, you can
bracket your exposures by 1/2 stops: two half stops over and two
half stops under or...
Place the gray card in front of your subject
and take a meter reading using it by first focusing on the artwork
and then carefully removing the camera from the tripod and moving
it in so that the gray card completely fills the viewfinder (do
not refocus or you will affect bellows factor). Then take your
meter reading making sure you, nor the camera, is blocking any
of the light or you will be measuring shadow. This should be the
proper exposure because you have provided the meter with a source
having an 18% reflectance value, which is what the meter is dying
to see.
Use a hand held incident light meter and measure
your lights directly. Incident meters are not influenced by how
much light is being reflected or absorbed by the subject. This
is the way they do it in Hollywood.
Take a reflected meter reading and an incident
meter reading and average the two together. Use this exposure.
If you have taken copious notes, you be able to determine which
method works best for you and finally exclaim, I am a great art
photographer! Just look at this!
Mark
D. Thellmann has been an art photographer, fine artist,
and photography instructor for the past 25 years. He has recently
produced a video entitled Take Perfect
Photos of Your Art and Craftwork which discusses and
demonstrates the necessary camera equipment, lighting, film exposure
and methods of photographing paintings, sculpture, woodworking
projects, fabric art and jewelry.
A second video entitled Alternative
Photographic Processes with Polaroid Films (time-Zero
film manipulation, image transfer and emulsion transfer) reveals
the techniques Mark uses to create fine art. These fine art images
can be found in the Polaroid Museum Collection and on greeting
cards and posters throughout Europe, the U.S. and Canada.
The videos are available from Show & Tell
Communications for $29.95 each plus $4 postage and handling. To
order, contact Show & Tell Communications: 856/488-9093. NJ
residents, add 6% sales tax. Visa and Mastercard accepted.
Mark Thellmann's artwork, displayed
on this site, is also for sale and available in many sizes.
Commissions accepted.
Please contact Mark Thellmann at Show &
Tell Communications: 856-488-9093 or markthellmann@aol.com.
All materials copyright Mark Thellmann.
No reproduction without permission. ALL RIGHTS RESERVED.
See
Part I , Part
II, Part III or Part
IVof Mark Thellmann's series
|
