At its birth about 1824, photography as practiced by its
first devotee, Joseph Nicephore Niepce, was a messy, all-
consuming pursuit that made use of such substances as
bitumen of Judaea, lavender oil, and pewter. Today,
chemical, mechanical, and electronic technology has made
photography a neat, transparent, facile technique which we
may easily apply to another messy, all-consuming pursuit:
gross anatomic pathology. Despite the amount of automation
available in photography, it is important to grasp a few
general principles, so that we may use to our advantage a
few powerful controls we have over the photographic
The main considerations in gross photography are , exposure
, focus, image size, composition, color balance, and film selection.
- I. EXPOSURE
This is essentially the problem of balancing the amount of
light coming through the lens with the sensitivity of the
film. We seek the ideal exposure and eschew the
underexposure (slide too dark) or overexposure (slide too
light). The determinants of exposure are:
A. FILM SPEED, measured as arbitrary standardized units
("ISO" or, formerly, "ASA"). ISO and ASA are numerically
equivalent units. The film speed depends on film
manufacturing process and type of development used on the
exposed film. Although films are packaged with a stated
ISO rating, some may be "pushed" to higher speeds by
special processing techniques. This should be kept in
mind before throwing away valuable film you have
mistakenly underexposed. The faster the film, the less
the resolution (causing increased "graininess"); also
colors are more subdued in fast film (such as Kodacolor
1000) than in "slow" film (such as Kodacolor 25). The
graininess and subdued colors of very fast films can be
used for artistic effect but are of no value in technical
photography. Therefore, we tend to choose slower films
for our gross lab cameras, so that we may produce
pictures with the greatest resolution and most accurate
color rendition. A film faster than ISO 160 should
probably not be used.
B. APERTURE, the setting of the iris diaphragm in the lens,
determining how much light is allowed through the lens
into the camera. Aperture measured as "f/ stops" (f/2.8,
f/4, f/16, etc). The f/ ratio is calculated by dividing
the focal length of the lens (see below) by the diameter
of the iris diaphragm opening through which light passes.
Therefore, the greater the diameter, the more light is
let in, and the smaller is the f/ ratio. Each f/ stop is
1.4 (the square root of 2) times the preceding f/ stop.
Each "stop" multiplies the amount of light by 2X. As an
example, f/1 lets in twice as much light as f/1.4 and
four times as much as f/2. The "speed" of the lens is its
f/ ratio at its widest aperture setting. An f/1.2 lens is
considered very "fast," while an f/5.6 lens is "slow."
Generally, fast lenses are more expensive than slow ones
and in fact do not have as good corner-to-corner
resolution as slower lenses. Because we generally have
plenty of light at our disposal in gross photography, we
opt for excellent resolution over lens speed. Most lenses
for our purposes are f/2.8 to f/4 at their widest
aperture settings. We typically choose to "stop down" our
diaphragms in most cases, because almost all lenses have
optimal resolution when not used at their maximum
aperture. The "ideal" f/ stop is generally taken as 2 to
2-1/2 stops "down" from the maximum aperture. For an
f/2.8 lens, therefore, the optimal aperture setting would
between f/5.6 and f/6.7. The other reason to stop down
from maximum aperture is to improve "depth of field" (see
"Focus," below). I personally shoot almost all my
specimen photos at f/8.
C. EXPOSURE TIME, or "shutter speed," measured in seconds or
fractions of seconds (1/30 s, 1/1000 s, etc) represents
the total time the film is exposed to the focused image.
It is determined by setting the camera shutter to open
for a specified length of time.
Effects of various shutter speeds:
1/1000 sec - 1/60 sec: These are OK for hand held camera
in existing light.
1/60 sec : Always use this with electronic flash, since
just about all flashes are specifically synchronized for
this speed. Using a slower speed (e.g., 1/30 sec) will
also work, but a faster speed (e.g., 1/125 sec) will ruin
the picture by failing to expose part of the frame. Note:
Some of the more modern and/or expensive cameras allow
flash synching at 1/125 second or faster speeds, but make
sure this is true of your camera before trying it.
1/30 sec - 1/2 sec : We tend to use this range for tripod
or copy-stand work, including gross photography. This
range is generally not acceptable for hand-held cameras,
because most people cannot hold the camera still enough
for this length of time. By using these slower speeds for
gross photography, we allow ourselves the luxury of
smaller apertures (giving us good depth of field and
maximum resolution from the lens) and slower films
(giving us maximum film resolution and best color
For example, each of the following exposure parameter set-
ups give the same exposure. Which would you choose for a
gross photograph taken on your copy stand, assuming you
have a camera with an f/4 lens?
- A. ASA 50 film; f/4; 1/30 sec
- B. ASA 50 film; f/8; 1/8 sec
- C. ASA 200 film; f/16; 1/8 sec
I would choose set-up 'B.' Set-up 'A' involves shooting
at maximum lens aperture, at which lens resolution is not
the best. Set-up 'C' lets us stop down the aperture for
good lens resolution but requires us to use faster film
with poorer resolution than the ASA 50. Therefore, 'B'
looks like the best compromise.
Even though a good copy stand will keep the camera
motionless and allow long exposure times, there is a
theoretical problem, called "reciprocity failure," which
may interfere with color balance in very long exposures.
But this is never a problem as long as you don't allow
the exposure time to exceed 1/2 second, and you'd
probably not notice it even if you shot a 2-second
exposure (which may occasionally be necessary when using
bellows at maximum extension; see below).
How do you determine exposure? There are two ways to do
Most cameras have a built-in light meter that monitors
the amount of light coming through the lens. This meter
attempts to optimize the exposure either by averaging
the total light hitting the film plane (an "averaging
meter") or using a small sample area (usually the
center of the field) to measure the amount of light
focused on that particular spot (a "spot meter"). In an
"aperture priority" system, the meter then looks at the
aperture you have set on the lens and automatically
adjusts the shutter speed to give the desired exposure.
In an "shutter priority" system, you set the shutter
speed and the light meter automatically adjusts the
aperture. These functions are available in what is
referred to generally as the "auto" mode. In addition,
most modern cameras have a "program" mode, which
completely automates exposure determination by choosing
both the aperture and the shutter speed for you. This
means all you have to do is compose the picture, focus,
and push the button.
Program mode has been a boon for photography in
general, because it allows you to concentrate on
composition and not have to worry about fiddling with
aperture rings and shutter speed knobs. There is,
however, a price to pay, especially in technical
photography. The main problem is that automatic
exposure systems (except in high-end cameras) are
standardized for snapshot type photography, where there
is no striking difference between background and
subject illumination. Also, an automatic exposure
system will attempt to make the subject have a
"neutral" brightness. In technical photography, we do
not necessarily want this; we want brain to look light
and spleen to look dark, just like these respective
subjects appear to us in real-time. Therefore, I do not
use the camera's automatic exposure system for routine
Because of the above considerations, I recommend that
you take advantage of the rigidly standardized exposure
environment of the copy stand and virtually always use
manual exposures. Determine the ideal exposure by
shooting a roll of film at various settings and then
stick with this exposure when shooting specimens. You
can still use the light meter when faced with an
unstandardized situation, such as having one of your
four floodlights burn out on Saturday and not being
able to find a replacement.
Parenthetically, I have found through experience that
when shooting documents of black printing on white
paper, you should use an exposure one stop brighter
than your standard setting for specimens. For instance,
if you normally shoot specimens at f/8 and 1/8 sec, you
should choose f/8 and 1/4 sec when shooting a document.
Never, never let the camera shoot black-on-white
printed documents on "Auto" or "Program," because the
camera will think you want the white paper to appear
neutral and will force a bad underexposure.
Another hint: When forced with shooting pictures on a
set-up you are unfamiliar with, you may have no idea
what settings to use. A good solution is to meter on
the palm of your hand (believe it or not, it makes no
difference what color you are; the palm of everyone's
hand looks about the same to a light meter) and note
what settings the camera's light meter indicates.
Simply switch over to manual and enter these settings.
Then you can shoot away and always get at least
There are two things to consider here, methods of focusing
and depth of focus.
A. Methods of focusing.
- Autofocus.Most manufacturers today produce autofocus
cameras aimed at various markets. The most popular of
these, aimed at the advanced amateur and the
professional, are probably the Minolta Maxxum series
and the Canon EOS. These cameras are packed with
automation which allow automatic film advance and
rewind, automatic and program exposure modes, and
autofocus. Automatic focusing uses a system whereby a
computer in the camera uses vertical lines in the
subject and focuses the lens by analyzing these lines.
I have not used autofocus systems in specimen
photography but have experience with them for snap
shooting. The problem is that if there are insufficient
vertical lines in the picture, the focusing system with
be fooled and can leave you with a terribly out-of-
focus picture. I have stuck with manual focusing for
specimen photography but would love to hear what the
autofocus aficionados have to say about its use.
- Manual focus. In this method you simply view the
subject through the viewfinder and turn a focusing ring
until the subject sharpens. If you have a choice, I
recommend a viewfinder with a split-field focusing
prism to help with critical focusing, but others prefer
a focusing grid, which, as far as I know, is only
available on high-end cameras, like the Nikon F series.
B. Depth of field
It is easy to focus on a flat object, such as a slice of
brain, but things get stickier when photographing objects
with depth, such as a windowed pediatric heart specimen.
Shooting these subjects requires a knowledge of the
concept of depth of field. It turns out that the zone of
depth at which the camera is in focus is greater at
smaller apertures (larger f/ numbers) than at larger
apertures. Therefore focusing is very critical when the
lens is "wide open" but much less so when "stopped down."
Let's say you are shooting an opened colon to
demonstrate, en face, a large villous adenoma. If you
focused on the "top" of the tumor (the part nearest the
camera) and shot the picture with the lens aperture at
f/2, the tip of the adenoma would be in focus, but the
sides would be slightly out of focus, and the surrounding
colonic mucosa would be totally out of focus and probably
not recognizable. However, if you stop down to f/16, the
entire specimen would be in focus. Since this results in
decreasing the exposure by six stops, you would have to
compensate by increasing the exposure time by a factor of
two to the sixth power, or 64. For good depth of field
and optimal lens resolution, I use f/8 routinely and
reserve f/16 and f/22 for subjects like the windowed
heart. Most cameras have a "depth-of-field preview
button" that lets you stop down the lens to its preset
aperture, so you can view how much depth-of-field you'll
end up with in the resulting picture (normally the
aperture diaphragm stays wide open until the instant the
picture is taken, so you have a nice, bright viewfinder
in which to compose the shot).
III. IMAGE SIZE
The size of the image in the camera depends on 1) the size
of the subject (of course), 2) the distance of the subject
from the camera, and 3) the focal length of the lens. The
focal length is the distance from the lens to the image when
the lens is focused on infinity. The effects of lens focal
length are as follows:
The greater the focal length,
- 1. The larger the image appears for a given distance.
- 2. The farther away from the subject you can be for a given image size.
- 3. The more critical the damping of camera motion to prevent blurring.
- 4. The slower and more expensive the lens.
- 5. The less the sense of depth and perspective.
- 6. The less the curvilinear distortion of straight lines.
- 7. The _more_ flattering to the face in portrait photography
(makes face less moony and nose less prominent).
- 8. The _less_ flattering to the body in figure photography
(makes subject look stouter).
Lenses are classified in groups based on their focal lengths
and other properties:
16 - 35 MM (WIDE-ANGLE LENSES). Rarely used in medical
photography, these are best for landscape and
architectural photography. They make landscapes look more
expansive and buildings more imposing. They tend to be
extremely sharp lenses that have excellent contrast.
50 - 58 MM ("NORMAL" LENSES). These are used for most
routine work, including gross photography. It is rarely
necessary to use anything other than a normal lens for
our purposes except when shooting close-ups so extreme
that the bulk of the lens shadows the subject, so that it
cannot be illuminated sufficiently. In this case you
80 - 135 MM(MEDIUM TELEPHOTO LENSES). These are used for
high-magnification macrophotography to increase working
distance, and for "over the shoulder" intraoperative
photography. For instance, you can be twice as far away
from the subject with a 100 mm focal length telephoto
than with a 50 mm normal lens and still get the same
image size on film.
200 - 2000 MM (LONG TELEPHOTO LENSES). These are usually
not used in medical photography but are indispensable in
sports, nature, and journalistic photography.
MACRO LENSES. Operationally, the only thing special about
these is that they have an extra long focusing extension
to allow you to focus on very close objects. They are
generally available in the "normal" focal length and the
medium telephoto ranges. For instance, Nikon makes two
excellent macros, a 55 mm and a 105 mm. Since they are
aimed at the technical market, macro lenses tend to have
excellent optics, are very durable, and are several times
more expensive than normal lenses of corresponding focal
lengths. Most macros in the normal lens category allow
you to focus down to objects close enough to give you a
"3:1" or "2:1" ratio; that is, the image size is one-
third or one-half, respectively, the size of the subject.
Most macro lenses can be used with an inexpensive
extension ring, which allows focusing down to 1:1 or
"life size," i.e., the image size is the same as the
subject size (Sigma makes a very nice, not-too-expensive
macro lens that focuses down to 1:1 without an extension
ring). This allows you to take some breathtaking shots of
otherwise unimpressive subjects, such as pituitary
adenomas. You can even make a corpus luteum look
VARIABLE FOCAL LENGTH (ZOOM LENSES). These are very
convenient for general photography, since you don't have
to move the camera so much. I am still waiting for
someone to come up with an affordable zoom lens that is
macro at all focal lengths and can focus on close
objects. Many of the lenses advertised as "macro-zooms"
are really just zoom lenses that allow close-up
photography only at a fixed focal length. When in "zoom"
mode, such lenses are not macro. Other zooms supposedly
have "continuous close focusing" throughout their range
of focal length, but the specs I have seen on these show
that they all have a minimal focusing distance that is
too long for practical use on a copy stand. My advice is
too stay away from zooms unless you are really up on the
capabilities of the individual models and know exactly
what you need.
BELLOWS. This is not a lens at all but simply a shade
that extends the lens very far away from the body of the
camera. This allows you to take true photomacrographs,
producing an image size up to three times that of the
subject. For instance, when shooting a 105 mm lens on a
bellows at full extension, the Lincoln Memorial on the
reverse side of a U.S. penny fills a 35mm frame. Multiply
this magnification by the amount you get when projecting
a slide in a lecture hall and you get some idea of how
Brobdingnagian a world you can present to an awed
audience. The only problem with the bellows is that light
intensity fall-off (as per the inverse square law) at
maximum extension requires you increase the exposure
accordingly. Also you have to be extremely careful about
camera motion, which is magnified correspondingly.
If you consider yourself more of a technical type than an
artiste, you are probably intimidated by this aspect of
photography. Although Ernst Haases and Edward Steichens are
probably born and not made, much technique of composition
can be easily learned by the average eye. In gross
photography, first step is good specimen preparation. This
is what separates the excellent from the mediocre; the
inspired pathologist from the drudge; art from mere visual
documentation. After you get comfortable with the camera,
you should spend almost all your time preparing the
specimen, with the actual photography being a brief
anticlimax. Here are some tips I find useful:
Cut away tissue that is of no interest, or that obscures
the interesting features.
Use props to position the specimen when necessary. A
slice of liver needs no props, but a gallbladder looks
better when you shove a few wads of paper under the
periphery to make it look like the saccular structure
that it is. Modeling clay is also a good material from
which to devise custom props.
Watch out for the obtrusive ruler. A lot of pathologists
remonstrate incredulously when I tell them I almost never
shoot a specimen with a ruler in the field. For one
thing, no one has made a ruler yet that is as unobtrusive
as I would like. Most specimens need no ruler, especially
full organs or full organ slices. We all know how big a
lung is; if not, we're only there for the free lunch
anyway. If you really want to know how big the lesion
was, just read the gross; it even gives all three
dimensions! If you really want to impress the conference
attendees with how big a goiter is, take a picture of it
with an everyday object, such as set of keys. Or, better
yet, bring the gross specimen to the conference and
ceremoniously drop it on the table with a loud thud.
I quit using rulers when I realized I never looked at
them except to marvel at how distracting they were. I
really don't think any one else looks at them either.
But if you're so anal that I can never convince you to
lose the ruler, do me a favor and shoot just one of your
frames on each specimen without it. I'll guarantee you
that nine times out of ten, that's the pic that you're
going to want to show at the conference.
Keep the background clean. This is a real pain, but to do
otherwise really compromises the photograph. It is much
easier to keep things clean when dealing with a fixed
specimen than a fresh, bloody one. On a related note, try
to keep the camera clean. Layers of dried gore
accumulating on the body of a tough Nikon F3 probably
won't hurt the camera, but it tends to gross out certain
people, particularly OSHA inspectors.
When photographing lungs or hollow viscera, use inflation-
fixed specimens when possible. You have to resist all
sorts of pressure from various circles to cut up the
specimen when it is in the fresh state, but, then again,
all great artists suffer for their work. I have yet to
see a gross photograph of uninflated, unfixed lung that
was any good. Inflation fixation of gut segments delays
your diagnosis a day but rewards you with gross
photographs that would bring tears to the eyes of any
Try to get rid of as much blood as possible. Otherwise,
the specimen ends up being just varying shades of red and
Watch out for distracting highlights. Fresh specimens
usually have very shiny surfaces that produce glare.
There are several things you can do to cut the glare on a
Formalin dip for just a few minutes; this preserves
color but dulls the surface; in overnight-fixed
specimens which have lost their color, soak in 70% EtOH
to partially recover color.
Turn off room lights.
Consider changing the lighting situation of your set-
up. Nice copy stands are usually set up with four big
floodlights. You may consider turning off the two on
the front of the stand and leave the two on the rear
on. Remember to adjust your exposure to accomodate the
loss of these lights.
Polarizer/analyzer filters do a great job, but the big
polarizers that go between the floodlights and the
subject are very expensive and fade out fairly rapidly.
H. Photographic backdrops. The choice of a proper backdrop
is essential for a professional looking photograph. The
best background is the one no one knows is there. Several
options are available:
Transilluminated light board with non-glare glass -
expensive; klutzes drop things on the glass and break
it; departmental business manager is incredulous at
expense of replacement and usually stalls its purchase.
Wet black velvet - less expensive ($12/yard); reusable
for a long time if you're careful; keep fresh, bloody
tissue off! Give each resident his/her own piece. Of
course, if you shoot anything that may have infectious
agents on it, you can't re-use the velvet, unless yuo
can find a way to sterilize it (another argument in
favor of shooting only fixed tissue).
Water immersion tray - Incredible shots of delicate,
"three-dimensional" objects make you into an amateur
Lennart Nilsson; solves problems of gravity and glare
simultaneously for such objects as villous adenomas,
chorionic villi, emphysematous lungs, etc. In my
experience, it takes quite a bit of patience to get a
good shot, as undesirable bits of grunge tend to float
into the field of view just as you are releasing the
Towel from surgery - sure sign of an amateur; an
embarrassment to say the least. However, if that's all
you've got, ask for a clean towel to replace the bloody
one they handed you the specimen on.
V. COLOR BALANCE
We perceive a sheet of paper illuminated by an incandescent
bulb to be just as white as if it were illuminated by direct
sunlight. This goes along with our concept that "white"
light is composed of light of all colors. This is true to an
extent, but various "white" light sources produce their
component colors in varying proportions. For instance, the
surface of the sun has a temperature of about 6000 Kelvins
and has much more blue light in it than the radiating
surface of a tungsten filament glowing at 3200 Kelvins,
which has more red light. This relation between temperature
of a glowing object and its color is well known to most
people (although not by its scientific name - Wien's First
Law), since we are taught from the fifth grade that a blue
flame is hotter than a red one.
Although the neurological visual processing system behind
our eyes compensates for this variability, the film in a
camera cannot. The solution is to make film where
sensitivity to the colors of the spectrum is specifically
balanced for the color distribution of the light source.
When shooting in daylight or with an electronic flash, we
need to use "daylight" film. Alternatively, when using
incandescent lights (such as the floods on the copy stand),
we need to use "tungsten" film. This is not some theoretical
consideration. If you try to use daylight film with the
floodlights you will get an unacceptably orange picture;
conversely, shooting tungsten film with a flash will produce
a picture that looks like it was painted by Picasso during
his "blue" period.
VI. FILM SELECTION
You will select film based on your need for good resolution,
your budget, the necessity of rapid processing turnaround
time, and the format in which your photographic work is to
Color transparency film. These yield the 2" x 2" mounted
transparencies known affectionately as "kodachromes" (in
the way that facial tissue is known as "kleenex"). The
actual frame size of the transparency is 24 x 36 mm.
E-6 process color reversal film (Ektachrome,
Fujichrome). Compared with Kodachrome (see below),
these are expensive; they have quirky color response
(being notoriously poor in rendition of eosinophil
granules, which look kind of dull purple rather than
vivid orange), and the slides fade with time (although
this may not be true of newer films in this category).
Nevertheless, the E-6 films are by far the most popular
in med center settings because of the ready
availability of the E-6 process. Most professionally
oriented processors can routinely turn around the film
in four hours. With a readily-available kit, you can
even process these films at home for about US$3 per 24-
exposure roll (plus a one-time US$30 investment for a
developing tank and reel).
Dye injection film (Kodachrome). Kodachrome is
superior in every way to the E-6 films, except that the
processing is slow and is usually done in large
reference centers where the film must be sent.
Eosinophils look great, and the slides last essentially
forever if stored properly. It is difficult to find
tungsten versions of Kodachrome, but the daylight
versions can be shot under tungsten illumination if a
special filter is used.
Color negative film (Kodacolor, Ektar). Also generally
available only in daylight versions, these films yield
color negatives which must be printed. It is preferable
to use color negative film for posters, rather than
having color prints made from your transparencies. This
is because color prints from transparencies usually
suffer from enhanced contrast that compromises the
accuracy of the rendition. When having color prints
processed, you must work closely with a skilled print
processor for good, publication-quality prints. The
automated printing machines used in "one-hour" facilities
are not capable of producing an accurate print from a
color negative of scientific subject (unless, perhaps, it
is a portrait of the scientist).
Polachrome film. This abomination of a transparency film
develops in a few minutes in a processor you can keep in
your desk drawer. It is extremely expensive, and the
dense emulsion makes slides too dark on projection; the
colors are less than impressive. It is best not to let
the clinicians know you have a Polachrome processor. They
will start giving you the conference cases even later and
will not realize how lousy the pictures are, while you
are grinding your teeth trying to find that audience-
pleasing mitosis somewhere on the screen.
Black-and-white film. Not to go into this at any length,
but you should use this for originals to be used for
publication. Black-and-whites made from color negatives
or transparencies are generally second-rate. Also you can
experiment with color contrast filters, which can really
Dr. Donald McGavin, Professor of Pathobiology, Univ. of
Tennessee College of Veterinary Medicine, generously
provided many fine suggestions from detailed review of the
first version of this paper, and I have incorporated most of
them into the current version. However, the opinions given
here are ultimately mine, as are any errors. I also wish to
posthumously thank my father, G. O. Uthman, who taught me,
among many other things, the basics of photography.
Please send any constructive comments about this paper to Ed Uthman, (firstname.lastname@example.org). I am
especially interested in correcting any errors that may have crept
Copyright (c) 1995, Edward O. Uthman. This document may be
freely distributed. It may be reformatted for purposes of
compatibility. It may be freely used for personal and
educational purposes, but it may not be used for commercial
purposes without prior written consent of the author. It maybe included in toto or in part as components of other
documents with proper attribution.
While I have made every reasonable attempt to include only
accurate information, it is very likely that some of the
information is wrong. Therefore, I am not responsible for
anyone's screwing up their pictures because of a naive
belief in everything said here.
Version 2.00, June 30, 1995
Published By: PathIT ©, a Division of Pisces Design and Consultancy, London N20 8HL
Created by the Documentation Center at AUB in collaboration with Al Mashriq of Høgskolen i Østfold,
970822/bl - Email: email@example.com