We have been developing kits to
photograph insects in flight since about 1975, back
in the days of film cameras and complicated home-built flash
units to get the requisite
short duration multiple flashes at the power required for 64 ISO
speed film.
Below is a photograph of the current state of our art.
A cover fits over it for storage or
transport. For scale, the base (almost the width of the first
image) is 1.13 metres long.
The black rectangular item just
right of centre is the normal trigger beam with
a pair of IR LEDs (Infra-red Light Emitting Diodes) and sensor
at the tip.
We can slide the box across the 'stage' to
allow for the insect's speed of flight.
The operator sits behind the sliding box and
tries to tease insects with soft paint brushes
to fly in the wanted direction. A bright
window in the wanted flight direction is a big help
except for some species of moth.
Inside the white box is a another
beam break (5 IR LED/sensor pairs) occasionally
used for different views. This used to be our primary flight
direction (towards
the camera at the right) but we get more flights and better
images with the
insects flying across the 'stage'. The setup is large enough to
include
the whole of the UK largest Dragonflies with a bit of margin.
The camera is on a mini sliding
mount looking left into the dark box but
focus locked onto the centre-line marked in white just below the
centre of the
first image.
There are 3 flashguns all
electrically (not radio or 'slaved') connected to the
camera:-
All of the guns run at very reduced
power, typically 1/32 (3% of
maximum power) in
order to get a very short flash to freeze the wing motion.
Details later.
The camera is set at X-sync
speed, F29 (very small for maximum depth of focus)
fast multi-frame and mirror locked up. The control electronics
'holds down the shutter'
for the time required for the camera to take 3 frames (or
however many you want
and the flashguns can manage)
Bottom left is the control
electronics:-
A small PC of great vintage with parallel printer port
used as control signals. It runs
MSDOS from Windows 95 but with the right fudges for port
access and a PCMCIA
parallel port card you could use anything. If we built
the kit again now we would use
a 'Raspberry Pi' and write the software
in Python.
A
large steel case containing sense amplifiers for the beam break,
and power supplies.
This content of this box is about 20 years old &
can't be re-built the same.
Ref: P34_20090503_1523_917 Flight
tunnel setup (ft1)(r+mb Sample@768).jpg 146K
Inside the large white box - the
painted background, replaced with black velvet and the
flash turned off for night flying moths and multi-flash.
Ref: P34_20090503_1524_927 Flight tunnel setup (ft1)(r+mb
Sample@768).jpg 108K
A clearer view of the camera and
flashes 1 & 2.
Flash 2 being on its side is fine because it is set to very wide angle.
Ref: P34_20090503_1524_933 Flight tunnel setup (ft1)(r+mb
Sample@768).jpg 126K
Another view of the kit configured
for strobe effects. Flashgun 1 is moved so as
not to illuminate the black velvet background, and is the only
flashgun used for this.
The exposure varies.
Ref: P34_20100917_1125_436 Flight Tunnel 1 multiflash strobe
configuration (orig)(r+mb Sample@768).jpg 148K
The electronics has been moved from
system to system and is very old.
The sense amplifier looks for sudden reductions in brightness
rather than
absolute levels so adjusts well for ambient light. This is the
decades old
schematic:-
Ref: Flight Tunnel 1 (FT1) Beam Sensor (web
size).gif
The setup is complex, and its a year
between main sessions, so we work from a check-list
that includes lots of setup details. The easiest way of
presenting this information seems to
be simply include the list with irrelevant stuff removed:-
Canon 1D Mk III CHECK LIST FOR FLIGHT TUNNEL - 19 Sep 2010
----------------------------------------------------------
Boot Toshiba Micro-PC into DOS (F8 at start of boot)
and start FLIGHTUN (else shutter is left pressed) &
CD \FLIGHTUN<enter>
F<enter>
(or continue from previous hibernation).
Flash cables into Camera Hot shoe.
Check Hot Shoe battery OK Light.
Select Flash power 'SE' for required guns
Load in Camera preset file:-
Settings include 1/250 sec, F29, Manual, Fast
Multi-frame,
MIRROR LOCK mode 2 (mirror STAYs up after
each shot)
30 minutes to power off, 160 ISO
No aperture board, Normal angled sky board.
STROBE flash:
Fit 16cm aperture board (stops flash
lighting background).
Camera changes from standard:-
Single frame,
ISO 250, Shutter speed to match MULTI.
Fill and background Flash: OFF
Main Flash: Move to Forward position
MULTI --- off,
1/32,
50Hz: Set
shutter to 0"3 (300mS = 16 frames)
or 80Hz: Set shutter to 1/5 Sec
(200mS = 20 frames)
FLASH: Position Gun Angle
Power Zoom
Main (Left)
5 90 1/32
50 (OFF FOR STROBE)
Normal: Mounted in raised rear position
MULTI: Mounted in low forward position extreme left.
Fill (Horizontal mounted
sideways under camera lens,
18mm = diffuser pulled out and over flash aperture)
3 90 1/64
18 x times y Hz as Requ.
Background
2 Dip 1/32
28 (OFF FOR STROBE)
Select Stage aperture size & Fit Canon 28-135 mm ZOOM.
Normally used at 105mm near closest focus.
Software shutter press time is 450mS to give 3 frames per press.
Test barrier & trigger selection.
Shutter release switch cable connected.
Up the Tunnel: Frame and Focus in
front of barrier.
Across the Tunnel: Frame & Focus on Cross flight line.
Lens to Manual Focus (if used to set auto-set focus).
Lens to Stabilizer OFF (if present)
Expose test card using a beam break - check required guns flash.
REGULARLY:
Check flash 'ready' lights
WHILE DISMANTLING: All flashguns to OFF
