CANON EOS FAQ Version 2.4
All original material is Copyright © 1992, 1993, 1994, 1995 Alvin
Chia-Hua Shih and Robert M. Atkins.
Date: November 1993
The "Canon Test Method" usually assumes optimum conditions. For
example, battery life on bodies is usually performed with the
lightest, cheapest lens (50/1.8 II), and that there are 20
seconds between exposures.
The typical EOS user is a user of zoom lenses, which are bigger
and heavier than the 50/1.8II. There is also significant battery
draw for simply metering the scene, even if no exposure is taken,
since all of the electronics power up, and AF is activated.
For tests involving flash, it is assumed that the flash is
exactly half discharged on every shot. With the A-TTL program, it
attempts to stop down as far as possible, meaning that the flash
is closer to fully discharged. With built-in flash, you lose
light because you probably don't have the 50/1.0L. That is to
say, you run into the guide number formula, distance =
GN/aperture, and thus require a full flash.
Some 2CR5 batteries may just not be very good. If you find a
brand that works well, stick with it.
The main draws of power are the electronics and motors. When
playing with AF you're activating motors. Also, when first
familiarizing one's self with a camera, one tends to leave the
display on for longer intervals. When any switch is pressed, the
camera electronics come on--even when the main switch is the LOCK
Here are three ways to test this assertion:
With the camera in aperture priority, set the minimum aperture
for the lens. Use hold down the DOF preview button, and then turn
the main switch to "L". Notice that the lens stays stopped down.
Remove the lens. It's still stopped down. Now reattach the lens.
As if by magic, the aperture opens again!
With a 430EZ attached, turn the main switch to "L" and let the
flash go to "sleep". Depress the shutter button or flip the AF/MF
switch. The flash wakes up!
Find a radio station that picks up RFI interference, and play
with the buttons. The electronics will come on and interfere.
[640 kHz works for me.]
Robert M. Atkins posted a nice summary of measurements based on
his 630. Newer cameras will draw more power due to faster CPUs
and more features.
From: email@example.com (robert.m.atkins)
Subject: EOS battery use - Some hard numbers
I just measured some current draw data for an EOS 630 with a
35-135 USM lens which might be of interest:
Lens focusing (infinity to close focus) 200mA for 0.25s
Film winding (1 frame) 600mA for 0.25 s
Mirror flipping up & shutter release 350mA for 0.1 s
Exposure determination (i.e. depress shutter
release 1/2 way to give exposure reading 100mA for 6 s
Film rewind (36 exposures) 450mA for 8.5 s
Any function button 100mA
(current is drawn until function is set)
Maximum current drawn was a 1.6 amp transient on motor start up
Adding up these numbers you find that to focus from infinity to
closest focus, get an exposure reading and hold it for 5 seconds,
release the shutter and wind on one frame takes about 835
mA.seconds. Let's be cautious and say I missed a few transients
and assume the real value is 1000mA.seconds. To expose a full
roll of 36 exposures and rewind it would then require close to
40,000 mA seconds. A 2CR5 has a claimed capacity of 1300 mA.hr (=
4,680,000 mA.seconds), thus we should be able to get about 115 36
exposure rolls from a 2CR5!! However, if you focus a couple of
times and take 3 exposure readings every time you take a shot
(which is not all that unusual for the kind of work I do), then
this number will drop by a factor of about 3, to maybe 40 rolls
per battery. This still seems a little optimistic - maybe 2CR5s
are not really 1300 mA.hr at the current draw rates
found in the camera?
The numbers do point out a few things thought. First, the small
USM lenses do not draw much power, so there would be little to be
gained by using manual focus. Second, the real power draw is when
the shutter is depressed 1/2 way to get the exposure reading. If
you don't take a picture you get 100mA draw for 6 seconds. If you
do take a picture the current draw stops after the frame is wound
(i.e. less than the full 6 seconds). Lastly, there is significant
discrepancy between the claimed capacity of 2CR5s and the
resultant theoretical number of rolls of film you should be able
to get through the camera.
Bob Atkins AT&T Bell Labs email (direct) att!clockwise!rma
Brett Cheng has supplied similar numbers for the Elan:
Subject: Elan Current Consumption Numbers (long)
Summary: test measurements of Canon EOS Elan power consumption
Keywords: Canon EOS Elan battery power
Sender: firstname.lastname@example.org (Brett Cheng)
All this discussion about power consumption in the EOS cameras
got me curious, and since I've been meaning to do some power
measurements on my Elan anyhow for some time, I thought I'd
investigate a little. These are just some quick measurements done
with what little equipment I have available at home, and I didn't
try to accurately measure durations of the transients. If I get a
chance some rainy day perhaps I redo these more accurately...
Bob Atkins recently posted a very informative list of
measurements on his 630. I haven't attempted here to break down
the consumption of the actual meter, shutter release, mirror flip
up, film wind, etc. of taking a photo as he did. I expect the
Elan is very similar in these respects, so this is not a repeat
of his measurements for the Elan.
However, since some other recent posts have been discussing
standby current and flash charge current, I've mainly
concentrated here on measurements relating to these or other
unexpected power consumption. I apologize for the length - I
think there are a few things of interest and of relevance to the
recent/ongoing battery discussion.
In particular, I set out to answer for myself these general
a. check the "L" and standby current (expected to be very low)
b. outside of the obvious items (motor wind, using flash, etc)
are there any other significant current draws?
c. is the built-in flash always charged, and will attaching a
430EZ change this as suggested in a recent post? (wasn't sure
about this one)
The test subject:
Canon EOS Elan, 28-80m f/3.5-5.6 USM lens,
Duracell-XL DL245A battery (2CR5)
Test method: definitely not Canon's Standard Test Method :-)
- Off and standby current is very low (both ~25 microAmps) so
removing the battery doesn't really gain you much.
- In fact, after reinserting the battery after a period of time,
the flash charges up at least partially.
- The flash in the Elan does always seems to be kept charged, or
at least mostly charged up. So when off (L) for a long period of
time, maybe no different from removing the battery.
- Attaching a 430EZ doesn't seem to affect this.
- With the camera set to "L", pressing the controls/turning dials
still causes some current drain.
- Aside from using built-in flash (also zoom flash, red eye
lamp...) which will obviously chew up batteries,
metering/focussing several times before each shot will waste most
power over that required for the shot anyhow (i.e. film advance,
- Don't leave the camera in IR remote/self timer mode for 15 days
or your battery will be dead :-)[editorial note: The self timer
will in fact cancel itself after a few minutes, so you don't need
to worry about this - RMA]
Details: (for those of you still interested)
First the measurements, numbered for later reference;
detailed comments follow...
Cmd Action/condition (mA) duration
1 L "off" 0.024 continuous
2 P "standby" 0.025 continuous
3 L turn QCD or
main dial 90mA 2 sec (!)
4 L press shutter
or any button 90mA momentary
5 L hold any button
except shutter 90mA 2sec max, then->standby
then 90mA momentary on
6 P press shutter 1/2 way,
AF off, no AF light
ie meter only 103mA 6 sec
7 L->P shortly after P->L 93mA 2 sec
7a L->P after camera off for
several minutes 200ma+ transient,
93mA 2 sec.
8 P turn QCD or
main dial 93mA 2 sec
9 P push AF mode button 93mA 2 sec max, then-> standby
90mA 2 sec on release
10 P push Drive mode
button 93mA 2 sec max, then-> standby
then 90mA momentary on
11 P push Drive mode button
& select self-timer
mode 3.6mA continuous while in self
timer/IR remote mode
12 P press shutter 1/2 way,
then AE lock 100mA until 6 sec after release
of AE lock
13 P focus inf-closest ~350mA <1sec (not too accurate)
14 P pop up flash 300mA <1sec (ditto)
15 P press shutter 1/2 way
red eye lamp on 280mA while shutter depressed
and lamp on
16 P after fire flash 2.2A peak decays to 500mA after
5sec, then -> standby
17 P->L after fire flash, immed
-> L 2.2A peak decays to 500mA after
5sec, then -> off
18 P->L after fire flash, immed
remove battery, -> L,
popdown flash, then
replace battery 1.9A peak decays to 500mA after
5sec, then off
19 P->L repeat 18 with 430EZ
attached & charged
battery 1.9A peak decays to 500mA after
5sec, then off
20 L camera in standby for
several minutes, then L.
Now remove battery for
several min, then
replace battery ~700m <1 sec, then->off
22 P rewind film (36exp 280mA(av) 14 sec
A. Standby vs. off seems to draw only very slightly more
(~1microAmp). So indeed storing the camera with battery in "L"
mode should last ~5.9 years. From this fact alone, I don't think
it's worthwhile taking the battery out for periods of non-use
(unless you're talking years of non-use)
B. Interestingly 3,4,5 show that even when camera is "off" (L),
the buttons are not completely disabled. I was surprised to find
that the main and QC Dials draw current for 2sec when camera is
off. So don't fiddle with those dials. Curious that "L" doesn't
actually disable those controls.
C. Item 6 is expected, matches similar measurement for EOS 630.
If you press the shutter 1/2 way a lot, this will be significant,
and this doesn't even include focusing. Aside actually taking the
picture (which you presumably need to do eventually :-) ), and
using the built-in flash, it still seems that metering/focusing
several times before the actual shot is the most wasteful.
D. Not sure what 7 is - you always get ~90mA for 2 sec when you
turn on the camera. This is likely the micro and other circuitry
starting up before entering standby - note all the other 90mA x
2sec items. But perhaps 7a could be the flash charge being topped
E. Item 11 is interesting, but not unexpected once you think
about it - standby current is much higher when in self timer/IR
remote mode. This would be because the IR detector has been
enabled. Leaving the camera in this mode for extended periods
could contribute to shorter battery life. However, if you set up
camera for self timer/remote photo and it takes you lets say
3-4min before you finish, the extra consumption for remote mode
is not much more than the consumption of a 6sec metering period,
so under normal circumstances this is nothing to worry about.
F. Item 14 - most of this is probably the flash zoom head motor
which moves the zoom head when you initially pop up the flash.
Similar reading @28mm. This reading was done with the camera
already on standby for a while. Item 15 shows red eye lamp is
another battery eater as expected.
G. No surprise here - 16 shows using the built-in flash is
expensive on batteries. The flash charge measurement is probably
not too accurate but I tried to catch the peak current and approx
H. 17-19 show after using the flash, it is charged up again even
if the camera is turned off - this along with 7a seem to confirm
earlier posts saying that the flash is always charged when the
camera is turned on and the battery is in. Having a 430EZ on and
attached doesn't seem to change this as someone earlier had
suggested. Didn't think it would...
I. I think 20 is similar to 7a, topping up the flash
charge...Perhaps if I waited longer, the current would be
greater? - I don't know, I didn't have the time to try... Anyhow,
this tells me that maybe the idea of some recent posts to remove
the battery after every use is maybe not such a good idea,
especially if it is true that the flash gets partially charged up
when you insert the battery. Then again, maybe no difference in
the end since with the battery installed and the camera off for a
while, the flash will discharge eventually and it will need to be
charged again (7a?). Probably need some more measurements
regarding this matter to be sure...
No. You can run the battery down until it's completely dead. It
can last for up to 2 rolls of shooting (maybe more). However, it
is a good idea to buy a spare battery by the time the camera
gives you one blinking bar.
No. The EOS cameras are designed to remember their state
information between batteries. On the EOS-1, there is NOVRAM
maintained by a lithium button cell. The cell is supposed to be
good for 3 to 5 years (under normal conditions). On the EOS 600
series, there is an EEPROM which gets updated. It is supposed to
last through 10000 updates. If it wears out, it will need to be
replaced by a Canon service centre.
I assume the 10s/Elan/A2/Rebel also have the EEPROM [RMA]
No. The shooting capacity of the A2/E is unaffected by the VG10.
(see 8.1.12 for details of the external battery pack)
Other than the obvious cutting back on the use of the built-in
flash, try setting CF13. Since metering is a relatively expensive
operation, and since it operates for a relatively long time, it
is probably a good idea to cut back if you can.
Harald Brandt reports that metering on the EOS 5 costs 150 mA
versus 23 uA for standby mode. By setting CF13, the metering goes
off immediately after the shutter button is released.
He also reports that Canon Sweden was able to lower the cutoff
voltage by 0.5V to prevent the camera from locking up before the
battery is totally consumed, and that he was able to get the
operation performed under warranty. Other Canon service folk may
not have heard of this, so keep nagging!
Here is an article posted by Harald Brandt [edited down a bit
because it covered some unrelated topics--ACS]:
From: Harald.Brandt@eua.ericsson.se (Harald Brandt)
Subject: EOS 5 & Battery life, Current drain, CF2, Flash
Organization: Ellemtel Utvecklings AB, Sweden
Date: Tue, 9 Feb 1993 18:37:00 GMT
CONTENTS: BATTERY WARNINGS, CURRENT CONSUMPTION [...]
In happiness of the new precious wonder camera, autofocusing and
measuring every possible spot around me, even loading a film
after some time, I soon noticed the battery symbol was half, and
after the end of the film, camera said I should replace with a
new one! In disappointment, I called Canon Sweden to complain.
This was how it started.
They said that especially the EOS 5 is set very (extremely) high
concerning battery warning. They have discussed this with Canon
Amsterdam (which handles all Canon questions for Europe, and who
in turn ask Canon Japan), and they have not gotten a proper
answer on why, except general mumble about very cold weather in
the northern Europe. Canon Sweden has decided to reprogram that
thing for anyone with warranty who complains about too short
battery life. The most fantastic thing is that they can do that
by simply connecting a cord to the flash contact on the top, and
then pushing a button on the computer! Very elegant! (They have
previously also done that on EOS10, and those people have been
The test/service program from Canon Japan contains the following
recommended thresholds (on battery check or after pushing the
shutter release halfway, i.e loading the battery with 150 mA):
Half symbol: 5.0 - 5.5 V
Empty symbol: 4.5 - 5.0 V
Flashing symbol: 4.0 - 4.5 V
With this, the shutter will be inhibited at about 3.5 - 4.0 V
Factory and service manual claim a "set voltage" of 4.2 V should
be used to obtain that, but Canon Sweden says that the above
thresholds will be exceeded by about a half a volt if set that
way, and have instead found that he "set voltage" should be 3.6
My camera was found to be set extremely high:
Half symbol: 5.8 V
Flashing symbol 4.8 V
Shutter inhibit 4.2 V
It is obvious that the above is a bit crazy, since even a new
Li/MnO2 battery will deliver, at the most, about 5.8 V under
Now, after adjustment, my camera has the following thresholds:
Half symbol: 5.2 V
Empty symbol 4.7/4.8 V
Flashing symbol 4.3 V
Shutter inhibit 3.6 V
I wanted them to measure current consumption on my camera to
check if it is OK. The following was measured:
Standby (Camera ON) 23 uA
Shutter button at half 150 mA (metering for 6 sec if CF13 is 0)
Rewind with film 400 mA (I think it was set to fast (CF1))
The above is within spec. (Wind (forward) should be 650-800 mA in
From the above, one can easily conclude that metering is very
expensive. It does not matter if you set CF4 (disable AF) since
circuits are either on or off (I have asked, but not checked
myself). However, current for AF-motor is not included in the
above values. It is extra, but only for a very short time (in
contrast to Nikon, where it drains until it after some time has
stopped hunting :-), don't be angry Nikon people, I am just
teasing, I have myself been a Nikon guy)
One can also conclude that if you forget to turn your camera off
for 24 hours, that corresponds to only 13 seconds of metering!!
Every 6 second metering drains 0.25 mAh from the battery, and
there are only 1300 mAh in it. So a good recommendation, while in
your playful mode (measuring and AF-ing every possible spot. I
still haven't passed that stage) is to set CF13 to 1, thereby
setting the timer to 0 sec. Alvin said that would cause trouble
if you want to shift exposure (not exp compensation) when in
program mode. Yes and no. It makes it a bit awkward but it is
possible: Use AE-lock button to get or lock exposure, shift exp
(main dial) press shutter release half way.
I have also CF4 set (inhibit AF when the AE/CF button is pressed.
Good fast alternative to turning the lens to manual when I want
to preset focus to some point, or when using AI Servo. But so
far, I can not claim to have a long habit of that way of working.
What's your opinion? (And by the way, What does the letters "AI"
stand for in "AI Servo"? It disturbs me that I do not know that.)
Best Photo Regards,
NOTE: See also section 8.1.10 for more information on A2/A2E
NOTE: AI stands for Artificial Intelligence
NOTE: I believe that Canon USA are unwilling to make voltage
adjustments to the A2/A2E unless the camera is outside the
official Canon specs. [RMA]
It would appear that "Not all lithium batteries are created
equal.". Canon sells a 2CR5 which is manufactured by Sanyo. Sanyo
and Panasonic are the manufacturers of "genuine" 2CR5 batteries.
All others are "equivalents" which may have different properties.
So, try out various brands to see which ones deliver acceptable
(see 8.1.12 if you have an A2/A2E)
In cold weather, the reaction rate of the chemistry within the
lithium cells slows down. When very cold (-36 degrees and below),
the reaction rate may slow down to the point of not being able
to power the camera. This is particularly true if the battery is
not at full charge.
One way is to keep swapping batteries in and out of a warm
pocket, forcing the reaction rates back up. However,this is
highly inconvenient when gloves are being worn, and may cause
missed opportunities during battery changes.
Canon recommends the use of the EOS 1, Power Booster E1, and
Nicad pack E1 (along with Nicad Charger E1). This setup is rated
for 30 rolls of 36 exposures at -20 degrees F. For those who do
not wish to invest in an EOS 1, Canon offers nothing.
However, there is a 3rd-party pack called an "UnderDog" from JVB
Designs in (of all places) Miami Florida. It is a small lead-acid
battery that can be attached to the bottom of the camera via the
tripod socket (note that there is no tripod socket on the battery
pack). A wire runs from the pack to a 2CR5-shaped module.
Since the EOS bodies are not designed for this sort of thing, a
notch will need to be cut into the battery covers of units like
the Elan, 10s, and Rebel. For the 600-series, the grip will
require modification. (The A2/E version is still undergoing
For extremely cold environments, the battery unit can be placed
in a pocket to keep it warm. When the battery unit is not
required to power the camera, it may be used as a low-voltage
pack for a flash in conjunction with the appropriate Quantum
The last known price for 2 batteries and a charger was
approximately US$150 The manufacturer can be contacted at:
PO box 53-0095
Miami, FL 33153.
or via Compu$erve at: 70671.1312@CompuServe.COM (John Van Beekum)
By the way, don't forget that power is only one consideration in
cold weather shooting. Watch for condensation problems (lens,
film, eyepiece,etc.), moisture in the flash, etc.
This information was gathered from Canon sources, however it is
not a direct quote from Canon and should not be treated as such.
The rate of battery consumption is different for the different
cameras in the EOS line. A lot of things influence battery
consumption, including the CPU speed of the camera electronics,
the winding speed (fps), the use of some functions such as eye
controlled focus (A2E) and of course the built in flash, red eye
reduction and so on. Thus the newer full featured bodies, like
the A2E, use more battery power than simpler models such as the
Rebel. The approximate order of efficiency (with no flash use) is
Elan, (Rebel and 630/RT), (10s and EOS-1), A2, A2E.
Battery use symbols. Basically you can use the camera up to the
point at which the shutter will no longer fire. The battery use
indicator is a guide, but the camera will function normally all
the way up to the point where it decides to prevent you from
taking a picture. The battery level indicator on the A2/A2E is
set differently from that on other EOS bodies, and may seem to
indicate the battery is running out faster than on earlier
cameras. Even though the manual states that you should replace
the battery when the battery indicator reads empty, Canon now
state that this is not needed. For maximum battery life Canon
recommend that you continue shooting until the shutter no longer
releases (just make sure you are not just about to get the shot
of a lifetime when that happens!). Depending on just how the
internal battery check levels are set you could get as many as 5
more rolls of film through the camera after the battery
indicator shows empty. On the other hand you may not get more
than 1 roll if the internal levels are set at the low end of the
Canon have set the point at which the shutter fails to fire at a
battery level which will give full camera function under the most
adverse conditions of camera use. For example for the A2E the
camera will quit when the battery voltage drops below the point
at which it could use eye controlled focus and built in flash
with red eye reduction at a temperature of -20C (4.2 volts for
the A2E). There is some discussion as to whether this is too high
(see the posting by Harald Brandt in 8.1.7 above). As far as I
know, Canon USA do not support the reprograming of the cutoff
voltage to a lower level. My guess, based on my own opinions
and not those of Canon, is that they do not want to lower this
voltage and run the risk of the camera operating improperly under
adverse conditions. With the lower voltage you might be OK
most of the time, but you could not be certain that every
frame would be properly exposed and focused when operating below
4.2v. Note that since the A2/A2E can draw more current than
earlier cameras, the battery voltage at cut off has to be set
higher to ensure full operation under all conditions.
Not all batteries are equal. A new 2CR5 should have a terminal
voltage of 6.4 volts. However the real test of the battery is
under load. Some batteries may read 6.4 volts off load, but show
a significant voltage drop when under load, while others may show
little voltage drop. Thus a "bad" battery might give a low
battery indication after only a few rolls, particularly on an
A2/A2E where the low battery threshold is higher than on other
cameras in the EOS line. In the absence of hard data it is
difficult to say which batteries are "best". If you get poor
performance, try a different brand. If you are happy with battery
performance, stick with the brand you are using. I have had good
luck with Sanyo and Panasonic batteries, but your experience may
The are no rechargeable 2CR5s at present. A NiCad of that size
would not have enough power to operate the camera for much more
than about 1 roll of film, not even that if you use flash. There
are rechargeable Li cells on the market with much higher capacity
than NiCad cells (3 or 4 times as much), but they are not yet
available in a 2CR5 package. Only the EOS-1 has the capability of
using AA cells, which are available in rechargeable form. The
only problem with the 2CR5 seems to be its cost, typically $12 or
so. However there is considerable mark up on these batteries. If
you buy in bulk they can be obtained retail for around $6. Rumor
has it that "Price Club" stores sell 2CR5s for about $6 also.
I have built a 4 x 1/3 AA cell rechargeable NiCad battery pack in
a 2CR5 package myself as an experiment. Note that you really need
5 NiCads to give you 6v, 4 will only deliver 4.8v - but you can't
get 5 1/3 AA cells into a 2CR5 shaped package! With a full charge
it will provide power for about 1 roll of film (36 exp) in an EOS
630 if you do nothing except press the shutter release each time.
If you do any kind of focus "checking" and exposure "checking" or
mess around with many of the settings etc. you probably won't
make it through 1 roll. Only if every 2CR5 battery store in town
was closed and you had to take a few pictures would this
approach be worth trying. My advice: Buy 2CR5s until someone
comes out with something better!
The BP-5 is an external D cell battery pack for use with the
A2/A2E. It consists of a 4 cell battery holder, a dummy 2CR5
battery, a 4 ft coiled cord and a dedicated camera grip cover.
List price is $75. Canon claim 200 rolls with alkiline cells or
100 rolls with NiCads at 20C/68F (cf 26 rolls with a 2CR5). At -
20C/-4F a 2CR5 will give 8 rolls, as will the alkaline pack, but
the NiCads should be good for 65 rolls. (all figure for 36exp
rolls, eye controlled focus on, 100% AE, 0% flash). An external
AA cell pack is currently under development by Canon, but as of
11/93 no details are available.
If all you want is "a little bit more", you might want to simply
shop more carefully when buying NiCad AA cells. Some cells are
rated for 600 mAh, whereas others for 800 mAh. Another option is
lithium AA's. Popular Photography stated that one set of lithium
AA's lasts about twice as long as one set of NiCads. However,
lithium batteries are expensive and are not rechargeable.
The 430EZ has a high-voltage jack. It is designed to accept power
from the Canon Transistor Pack E. With it, recycling time can be
reduced to 3 seconds and shooting capacity is on the order of 250
full-powered flashes with the NiCad Pack TP. The Transistor Pack
E will accept 6 "C" cells, or a special NiCad pack from Canon.
Canon does not recommend using NiCad cells in the Transistor Pack
E. (I have no idea why not.) Canon warns the 430EZ can be damaged
from overheating if fired at faster recharge rate provided by the
Transistor Pack E. Canon has recently added the "Compact Battery
Pack E". It holds 6 AA cells and also plugs into the high-voltage
pack. It may be attached to the camera via the tripod socket, or
put in a shirt pocket, or attached to a belt via the included
carrying pouch. It is rated for100 full powered flashes with
Canon doesn't recommend the use of non-Canon high-voltage packs
(of course), but no reports [to my knowledge] of a 3rd-party pack
damaging a430EZ have been reported. The most popular 3rd-party H
packs are based on lead-acid technology. To attach the pack to
the 430EZ, an additional adaptor cable is required. Damage to
your flash as a result of connecting to a 3rd-party pack will (of
course) void the warranty.
A low-voltage pack.
A low-voltage pack.
A low-voltage pack connects to the battery terminals of the flash
and delivers 6V at a slightly higher current than NiCads would
normally provide. Some packs are just big NiCad batteries. Others
are lead-acid. To get the power from the pack to the battery
terminals, a matching "battery adaptor" is required. These
adapters are designed to fit into the battery chambers of
specific flash units. Since there is no opening to run the cable
to the battery adaptor, the door to the battery chamber must be
left partially open, or a notch must be cut into the door. In the
case of the former, the battery door is usually held shut with a
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