Newsgroups: rec.photo
From: john@nmt.edu (John Shipman)
Subject: Shoulder mounts for bird photography (long)
Originator: acs@genie.csri.toronto.edu
Organization: Zoological Data Processing
Date: 7 Jan 93 10:46:08 GMT

There has been a fair amount of traffic in the BIRDCHAT
mailing list lately on bird photography.  In reply to this
traffic, I have prepared two postings on little-known
techniques (shoulder mounts and flash projection) that have
proved especially useful to me; I thought you folks on
USENET might also find them useful.

1. CAMERA SUPPORT AND PHOTOGRAPHIC STYLE

The debate on this mailing list so far seems to be between
the tripod fans and the hand-held fans.  But I maintain
that a well-designed gunstock (or shoulder mount, as it
is known in photographic circles) can be superior to either
for the style of work that I prefer.

I hate trying to photograph birds with tripods.  The only
thing I use a tripod for is to hold up my scope.

The type of bird photography I prefer is not for everybody.
My principal aim is documentation.  I generally bird alone,
which can lead to credibility problems when you see
something rare.  A nice crisp slide can be very convincing.

For those rare situations when the birds cooperate, I like
action shots---birds in flight, taking off, landing, or
walking---and dramatic closeups.

For this type of shot, portability is a great virtue.  You
can get wonderful pictures with an 8"x10" plate camera and
three strobes from the top of a 60' scaffold two feet away
from a nest.  Noel Porter and Eric Hosking did all this
decades ago, but it isn't a very portable style.

2. THE STALKING STYLE

My ideal is to have a rig that is as ready to wield as a
cowboy's six-shooter---something you can draw and aim in
seconds.  Also, sometimes I like to work in salt marshes or
climb over fences.  Try setting up a tripod or even a
monopod in some really nice semi-liquid mud, or on a
boardwalk 12" wide.

I often stalk nervous targets, and this means minimizing
any sudden motions that might be frightening.  Setting up a
tripod is out of the question.

I find using a camera on a tripod to be a very unnatural
process.  When the bird is moving to the right, you have
to move the camera to the left.  Using a shoulder mount
is like using a rifle; you are basically pointing at the
bird, which is a more natural motion of your arm.

3. LENS SELECTION

How long a lens?  This depends on the size and steadiness
of the user.  For the stalking style I prefer, anything
shorter than a 400mm is just too frustrating, and the
longer the better---500mm or even 600mm.  My first
published photo, a Trumpeter Swan in New Mexico published
in _American Birds_, was taken through a Questar working
at around 1500mm---not from a tripod, but on a shoulder
mount, braced against the car window.

The small, lightweight mirror lenses (usually around 500mm)
seem like a great idea for bird work but many who try them
have difficulty getting good results.  What I recommend for
this application is to use a shoulder mount that is NOT
necessarily as light as possible!  Two or three pounds of
oak, for example, can add enough mass to the optics to stop
them from bouncing around and make it a lot easier to see
when you have achieved critical focus---and this is one of
the REAL battles of photography.

When you are taking pictures of small subjects like birds,
depth of field is a serious problem.  An interesting fact
from optics is that the depth of field does not depend very
much on the focal length of your lens---it is mainly a
function of the reproduction ratio (the ratio of the size
of the subject to the size of its image on the film).  When
you are working near the close-focusing limit of a fast
telephoto, your depth of field may be measured in
*fractions* of an inch!  Therefore, achieving critical
focus, especially when you or the bird may be moving, is a
lot harder than it looks.

A 90-lb. woman of my acquaintance really likes the 400mm
Novoflex Follow Focus system with an Olympus body.  This
system has an integral shoulder mount that is adjustable
for length and angle.  The lens is decently sharp; it may
not be quite as tack-sharp as the Japanese and German
lenses that cost as much as a compact car, but for people
with realistic budgets it is a good buy.

I have found that the ultimate sharpness of the lens is
seldom the limiting factor in bird photography.  Much more
often, I find that the real battle is to get the shot
critically focused and the exposure correct.  Steadiness
(and a good focusing screen) really help in focusing.  None
of the microprism focusing screens work with long
telephotos; get a body that accepts interchangeable screens
and switch to one of the all-matte varieties.

I routinely shoot my 600mm rig at 1/250 and even 1/125 if
I'm well braced (out the car window, against a fencepost).
Even in a situation where you have no support, like the
middle of a marsh, sometimes 1/250 will work if you're
steady.

4. DESIGNING A SHOULDER MOUNT

I have looked at several commercial shoulder mounts, but
the best solution is to make your own, or find a friend who
is handy with tools.  My current rig was constructed by my
friend, neighbor and birding companion Phillip Johnson.  He
used mostly aluminum structural shapes (1" aluminum
U-channel, square-section and angle) and pieces of an old
maple cutting board.  It is much lighter than the (rather
heavy) camera components, about 2 lbs. versus 12 lbs. of
lens, body and motor.

I haven't the time to answer individual letters about how
to design a good shoulder mount, but here are some general
principles that have worked out in the designs I've looked
at.

One of the reasons a custom design beats a commercial
design in most cases is that it can be made to fit your
body and your optics.  It is hard to design a commercial
product that can adapt well to the wide variations in the
location of the tripod socket of various cameras and
lenses, not to mention the various shapes and sizes of
people.

For small, light optics, you can probably get away with
just providing a tripod mount (1/4" x 20 thread) for the
lens, or just the body.  But for the heavier and bulkier
optics, you should consider providing tripod mounts for
both the lens and the body.  The particular optical rig I
use is a 300mm lens with a 2x teleconverter, and the
teleconverter is not designed to put up with a lot of
stress, so in my case a primary function of the shoulder
mount is to hold the lens and body in rigid alignment with
each other so there is no strain on the relatively delicate
teleconverter.

(Since everyone always asks, I prefer the doubled 300mm to
the regular 600mm because it focuses much closer, 13'
instead of 25', and I often get close enough to birds to
care about this difference.  After considerable testing I
concluded that there is no loss of sharpness with a
high-quality teleconverter, as opposed to the $40 Vivitrash
model.)

One critical design principle is to provide as many points
of support as possible.  My rig has four points of support.
My left hand operates the focus ring, and my left elbow is
braced against my rib cage.  My right hand operates the
camera controls (motor trigger and exposure controls) and
my right elbow is also against the ribs, so my arms both
form triangles.  There is a wooden shoulder piece that sits
on my shoulder.

My rig also has a cheek brace.  This is an idea from rifle
design: gunstocks are often designed so your cheek rests
against the stock in shooting position.  On my rig, the
cheek brace is a piece of maple with a small hollow rasped
into the end.  When I put the rig against my shoulder and
fit my cheekbone into this hollow, my eye is automatically
centered in the finder.  So the cheek brace indexes the eye
position and also provides a fourth point of support,
allowing me to use my neck muscles to steady the rig
further.

If your camera has the usual hinged back, you will probably
have to design the cheek brace so that it swings out of the
way while you are changing film.

Below is a pathetic attempt to illustrate the design of my
rig using ASCII characters.

                                            _____
     I                                     /     \
+--------------------------------+         |  c  |
|    a       a'     a''          |         |     |      _____
+--------------------------+-----+         |     |     /    /
    [I]                    |  e  |   I     |     |    /    /
                           +-----+-------------------/    /
                           |         b        x     / d  /
                           +-----+-----------------/    /
                                    [I]           /    /
                                                 /    /
                                                ------

Key:
  a. Mounting screw for the lens (with 2x teleconverter)                
  a', a''.  Alternative mounting holes for use with 1.4x
            teleconverter (420mm) or no teleconverter (300mm)
  b. Mounting screw for the body
  c. Cheek brace (pivots back around point x for film loading)
  d. Shoulder piece (slightly concave to the rear)
  e. Spacer, height depends on relative body/lens spacing

Elements a and b are 1" aluminum U-channel; element e is 1"
aluminum square-section; and elements c and d are maple.

5. HARNESS DESIGN

After fighting with straps of various designs, I eventually
decided that what I wanted was something more like a
harness.  I made a harness from 1"-wide webbing stock and a
locking carabiner (both available at your friendly local
mountain-climbing supply store), and stitched together
using 50-lb. test Dacron saltwater fishing line in a
darning needle.  The harness distributes the weight of my
rig to both shoulders.  Initially I thought I could get
away with using a regular (non-locking) carabiner, but
changed my mind the first time I dropped the rig.

Here are front and back views of my harness design:

    ___               ___
   /   \             /   \            Basically it is a figure-8
  |     |           | o o |           of webbing.  You put your
   \   /             \ - /            arms into the loops of the 8
    | |               | |             which are connected in the
  \\   //          ||     ||          middle of the back (at the
   \\ //           ||     ||          point marked with a star);
    X*X            ||_____||          a separate piece of webbing
   // \\          a||-----||b         is attached across the
  //   \\          ||     ||          loops (points a-b) in front.
                                      Attach a carabiner at point
 Back view         Front view         "a" for right-handers, which
                                      hooks to a ringbolt on the rig.

I would like to hear from anyone who has tried a commercial
shoulder mount that they could stand.

John Shipman (john@nmt.edu)


-- 
John Shipman/Zoological Data Processing/Socorro, NM/john@jupiter.nmt.edu
``Let's go outside and commiserate with nature.''  --Dave Farber

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