This is a tale about trying to find the best battery replacement for a
classic Minolta SRT 101.A
black Minolta SRT 101 was my first "adult" camera in 1970.I recently decided I should again have a Minolta SRT 101.I ended up with two SRT 101 bodies while collecting the lenses I
wanted.Although both bodies
were clean and mar free, they needed new seals and I detected the
slightest of possible delays at some shutter speeds.Both went to my long time repairman for a CLA (Clean, Lube, &
Adjust) and new seals.
Upon receiving the camera bodies back I was confounded that they were
both equally smooth, crisp, and seemed to function wonderfully.Now to the reason for this posting.What battery to use.
I thought the best solution would be easy to come by.The original PX625 mercury batteries that these camera used from
the factory are no longer available in the US.I had read online different possibilities.Different people had different opinions.While many said which battery solution was best, and gave general
reasons why, none seemed to have actually compared the possibilities and
provided the results.This
has lead me to actually document my process of finding the best possible
solution to this problem.I
have attempted to do that here.
As I have stated at other times, I am not a camera repairman.I am not an expert.I
am mechanically inclined and at the time could not find a detailed
comparison on the internet.
I decided to approach the problem by testing three available
solutions.Testing would
consist of comparing the readings from each solution on the Minolta
pair, against the readings from my Canon 5D Mark III, and Sekonic Light
Meter.Only fresh batteries
were used in all devices for the testing.
The Three Minolta Solutions Tested--
1) Duracell recommended replacement battery for the Minolta SRT
101 (PX625ABPK Alkaline Battery, 1.5v)
2) The Paulbg.com adapter ring which is designed to allow usage of a
smaller hearing aid battery (ZA675 Zink Air Battery, 1.4v)
3) The CRIS MR-9 which is an adapter allowing a commonly available 1.55v
battery to fit into the adapter and when placed into the camera
circuitry reduces the voltage output to the desired 1.35 volts
(Energizer Silver Oxide 386 Battery 1.55v).
Methodology--
--3 different constant lighting conditions were used to compare
the exposure results: Strong Light, Medium Light, Lower Light
--2 aperture settings were used for each test: 1 Stop From
Largest Aperture (f4) and 1 Stop From Smallest Aperture (f11)
--The same lighting scene was used by all devices for each
exposure reading
--The control devices have previously been tested to ensure their
relative accuracy
--Test exposures were recorded with each device at both aperture
setting, for a total of 6 exposure settings for each device
--Both Minolta's used the same MC Rooker 35mm lens
06/17/15 - All three of the below solutions will only work in
cameras that compress the positive and negative sides of
the battery togather in some form for good contact. Cameras like the Canon Canonet
QL17 GIII have a slot where the battery is placed sideways into an
existing slot. The battery must in these cases be of exact
thickness. Some of the below replacement batteries are thinner
than others and thereby may not fully making contact with both the positive and
negative sides.
The 675 battery size solution listed below will NOT easily work in a
Canonet QL17 GIII. The 675 is approximately 20 thousandths thinner
than the other two batteries and will not work in the Canonet and some
others without something to make up the additional thickness, such as
aluminum foil.
This also applies to the Wein 1.35v battery........
Proposed Solutions--
The easiest off-the-shelf solution, Duracell 625A, 1.5v "Photo"
battery.Marketed by
Duracell as a drop in replacement for the Minolta SRT 101 and other
cameras that originally used the mercury PX625, 1.35v battery.No adapter or other modifications required.Insert into camera and use.
The cost is straght forward for this solution (One Size 625A Alkaline
Battery = $3.59)
The second solution for Minolta SRT 101 and similar cameras.Requires purchase of an adapter ring from Paulbg.com in England.Said to be a onetime adapter cost as it can be reused repeatedly.To be used with one of several 1.4v Zinc Air readily available
hearing aid batteries.Here
is shown a size 675, 1.4v Zinc Air battery from Walgreens, a pharmacy
common in the US.Battery
slips onto the ring, and the setup into the camera.
(Some have used this battery without the above ring by either adjusting
the cameral tension or using an O ring or something similar to fill the
space)
06/17/15 - If you go to a hardware store and ask for a #9 plumbing
O-Ring, it will work perfectly.......
The cost of this solution is (Paulbg Adapter = $7.23ea + Shipping =
$2.46 + One Size 675 Zinc Air Battery = $2.12 x 4 for Pack)
The third solution for Minolta SRT 101 and similar cameras.Requires purchase of the C.R.I.S. MR-9 adapter.Also a one time cost as it can be reused repeatedly.In this unique solution a commonly available 1.55v size 386
battery fits into the adapter.The adapter is the correct size needed and contains circuitry
which converts the 1.55v battery output to the required 1.35 volts that
the camera originally used.
This is the most expensive solution (MR-9 = $36.99 + Shipping = $8.50 +
One Size 386 Silver Oxide Battery = $1.80)
Results--
*Minolta SRT 101 #1 - #2604731.#2 - #1489639
** A + or - character after the
shutter speed indicates that the exposure was not exactly centered in
the ring.If the needle was centered in the
middle third of the ring, no plus or minus was used.If needle was in the upper third of the
ring I used +, meaning 1/3 to 1/2 stop more exposure was indicated.If needle was in the lower third of the
ring I used -, meaning 1/3 to 1/2 stop less exposure was indicated.
Conclusions--
I was surprised how little exposure difference the three
solutions made overall.
Before a studio photographer jumps in and states that a 1/3 to 1 stop
difference is important, I would like to add that this can be
compensated for.With the
Minolta you can adjust the film speed ring by 1/3 of a stop.By understanding how the battery functions in your camera,
exposing a test role, and then for all future exposures adjusting the
film speed setting on the camera accordingly, a person can have correct
exposures that are as accurate as the camera metering system is capable
of achieving.
The Canon 5D Mark III and the Sekonic light meter were both
almost exactly in sync with only minor differences in a couple of spots.I think that this can a attributed to some differences in the
light gathering area between the two.
I will let people look at the data and draw their own detailed
conclusions.The number of
times that test camera 1 had the lower exposure compared to test camera
2 were too similar form me to draw a conclusion as to which camera
underexposed throughout the test.
The number of exposure differences between the two test cameras
did drop with each solution that was closer to the factory required 1.3
voltage
---1.5v solution had exposure differences between cameras on every
comparison
---1.4v solution had 4 of 6 exposure comparison differences between
cameras
---1.35v solution had 3 of 6 exposure comparison differences between
cameras
The four times that the exposure differences between the 2
cameras was more then 1 stop difference might be explained by slight
changes in the lighting between test shots.I did not use a studio setting for the tests.Exposures were conducted in the daylight, ensuring that no cloud
cover occurred during the test shots.That is not to say that a high thin cloud could not have passed
in front of the sun during one or more exposures.......
Battery depeletion curves were not taken into consideration for
these tests.There are other
sources out there that provide drop off curves for the batteries in
questions.It is something
that needs to be considered.
The reason that the camera manufacturers went with the mercury battery
is its sharp drop off shoulder.That battery would remain at or near the 1.3v output level until
just before it went dead.
The other batteries tested here however have a different curve and would
likely start out with the full voltage, but would slowly fall until
unusable.This is another
factor that must be considered in your choice.I personally removed it from the equation by factoring in the
decision I would ensure I always placed fresh batteries in the camera
every time I used it.
Bottom line to me is that I think a person could successfully use any of
the three solutions to power their camera exposure meter if they are
carful.There is significant
cost difference between the solutions.It is close enough that each person will have to make up their
own mind which path is best for them.
I hope you enjoyed the comparison.
Bruce Varner
*Caution - The results above only apply to the Minolta SRT 101
and more precisely to these two 101's.Whether you would get the same results cannot be guaranteed by
the above tests.Fair
warning!
