Saturday, September 11, 2010

Batteries or Rechargeable

The intro picture has nothing to do with today's experiment except that I used batteries in the SB 900. Normally one tries to avoid a sharp shadow from the flash but in this picture I wanted the shadow to repeat the form of the sculpture on the little tower. The picture was taken in the castle of Gruyere/Switzerland . The sculpture is from the artist HAFIS. The old White balance and gel the flash technique is much stronger here due to the rusty surface.

Now back to on topic: The Metz 45ers get their power from one of three sources: A battery cage or a rechargeable pack that are inserted in the bottom of the grip, or and external battery pack.
Today we look at the internal sources only and ignore the external packs for the time being.

The flashes are delivered either with a battery cage to be filled with 6 AA (or mignon) cells. Some versions are delivered with a Metz rechargeable pack where 6 rechargeable cells are in a pack cage and a dedicated recharger. The individual rechargeable cells of the rechargeable pack can normally not be changed or taken out by the user.

Now we all know that the old NiCD rechargeables are a pain in the ass. They need constant fussing about, care and maintenance to work properly. So they have not been very practical for anyone without a full time assisitant, to whom to delegate charging and de-charging the packs once in a while and re-charing them at the right time. Whenever you wanted to do some shots at the spur of the moment the packs were not fully charged. Charging on top of the current charge provoked memory effect, which had to be healed later with days of charging and uncharging.
A complete un-charging and re-charging took 4 hours at best.

For most hobbyists the rechargebale pack went inbto the closet and the flash was operated with batteries in the battery cage. 2000% less hassle.

Later the NiMH rechargeables and the eneloops (like NiMH but hold the charge longer) came to market which made life a lot easier. Many people used a electronic charger like from Ansmann with 6 loading bays and one or two sets of NiMH or eneloops and popped them into the battery cage and went from there.

However (there seems to be always a however) the flash units have 3 pins in the power bay and the connection pins from the battery cage and the rechargeable pack are different.

There has been endless debate in many forums if it makes a difference in practice to put your rechargeables into a battery cage. Some people have posted nice instructions on their blogs how to dissect an old Metz Rechargebale pack with NiCd cells and replace them with Eneloops. Of course that has the drawback that you will habce to get a new charger as well, and it needs to be a charger that can charge the cells when they are connected in a row together (in the pack).

One nearly spooky aspect of Metz as a company is their efficient customer service. Ask any question on their website and you will receive an answer normally within two business days that not only answers your question but also some taht might be connected and for good measure throws in all manuals in pdf of all parts that were mentioned. I don't know how they keep up that stellar performance in this day and age, but way to go Metz!

The customer service is cited of explaining that older models suffer from less power, when rechargeables are used in the battery cage, newer models have a new electronic and it doesn't matter anymore. Still many posters in the forums insist that they do not see a difference in practice.

The reason for the two seemingly contradictory statements is simple. As explained earlier, one of the big advantages of automatic flash is, that the "unused" power is stored for the next shot. So if you have a realtively large aperture like 4 or 2.8 and shoot in Automatic or TTL mode, the flash might only use 20% to 50% of its power depending on distance and subject. So if the "fully" loaded flash has only 95% instead of 100% power, one might never notice.

However I intend to do experiments later on where we test limits of automatic flash and compare the 45ers to the modern hardware, I would like to know, if there is a difference in the flashes I own and how much is the difference.

And that brings us to today's experiment:

Three battery cages with: left fresh batteries, middle NiMH freshly re-charged, but well used and on the right the new NiMH recently bought and charged and no longer fully charged. Kind of a usual mix that can be found in any Hobby Strobist's bag.

Not in the picture but also used is a Metz NiMH pack (from 2009).

First I determined the current voltage of all packs:

The batteries gave 9.5V which is 6x 1.6 not unusual for fresh out of the pack.

The older NiMH gave 8.1V which is 6x1.35 again higher than nominal but not unusual fully charged.

The newer NiMH gave 7.85V which is 6x1.31, still well above nominal.

The Metz Pack gave also 8.1. Notice the difference in contact pins.

The set up is as follows:

- I tested three different flash types 45 CT5, a 45 CT4 and the newest 45 CL4 digital.

- The flashes were connected to my D300s (all of them are safe, I measured the trigger voltage) shooting a corner of a room. The motive is a grey felt cloth clipped to a light stand.

-Each flash is fired with full power in manual mode, the output is measured by a Gossen Lunasix used as flash meter.

-Ambient light is very low, curtains are drawn. The ambient light measurement would have been 1/4 second at f4 as determined by the camera.

- The camera is set to 1/60 and f/11 as determined by a flash meter reading, which is 7 stops above ambient level. A test shot without flash at this setting is completely dark (not shown)

- The camera and the light meter are set to ISO 200.

- Absolutely unnecessary as we will shoot full manual the flashes are also set to ISO 200. Just for fun.

The camera and flash (in this example 45 CT5) looked like this:

I like the display on the 45 CT5. If it is on a tripod it might not be easy to look on top. It is nice to see on the backside what has been set by wheel on top.

Test 1 45 CT5

Flash meter reads 16.1 which is f16 and a 1/10 stop

(The Gossen measures in 1/10 of a stop and gives a decimal reading)

The New NiMH (eneloop type) noticable darker.

Flash meter reads 11.6
Oha! that is a half stop less!

The usual NiMH type.

The flash meter reads 11.7.

As expected nearly same result. 0.1 stop difference is within tolerance.

Test 2 45 CT4

Despite the lower number a newer model that replaced the CT5. Basically the same result. I do not repeat the pictures.

Test 3 45 CL4 digital

All variations I tried including the newer Metz recharge pack and an old Metz recharge pack produced the same result.

They did really improve the electronics quite bit!

The meter read in all instances exactly 16.9. The 0.8 difference to the first shot above come from the fact that I used the wide angle adapter on the first two flashes and not on the CL4 digital.


1) The current models like CL4 digital don't care what voltage is delivered and always deliver constant output including maximum output.

2) The older models deliver around 0.5 stops less maximum power when rechargeables are used in the battery cage. more so there seem to be slight variations in maximum power depending on the actual voltage of the power source.

3) The wide angle reflector causes a drop of 0.8 stops maximum power. (the manual says 1 stop)

Open questions:

Which models are exactly with the new cool electronics?
When using automatic how much do I have to deduct from the maximum distance indicated when using rechargeables?

Answers soon


  1. Using the 45 cl-4 what I have found is as follows.

    Setting the flash at Manual full power.

    I get a reading of f11 at 10 feet.

    When I change the setting to half and quater power I get the same reading.

    Two anomolies.

    One is that the power is less than I would have expected, ( with either battery type).

    Secondly I would have expected the result to be different when the Manual settings are changed to full, quarter and half power.

    The forgeone is the results when using a flash meter and without the diffusers.

    In practice when I use my studio grade digital camera and repeat the change in settings on the flash while keeping the f stop on the camera I do get Both an increase in percetable power as evidenced by having to set the camera to f16 instead of f11 AND there is a vast difference in the results when changing from Full to Half and Quarter Power.

    In summary

    It would appear that the flash is working correctly and as stated BUT for some strange reason a meter can not be used to prescreen the results.

    My theory is a follows.

    Using the Manual flash setting one is NOT adjusting the output of the flash at all.

    Rather one is changing the duration of the flash NOT the power.

    Much like changing the shutter speed on a camera changes the exposure without changing the intensity of the light source.

    This phenomenon appears to be relavent to Thyristory type flashes as other NON thyristor flashes that I use do not exhibit this affect.

    My question then is this:

    How does one actually measure the output of a flash or alternatively do we simply pre test our shots first.

    Thank you

  2. Your test is base on "normal" battery holder(6x1.5V).The battery connection to the Metz is position 12 o´clock for "+" and position 7 o´clock for"-".
    Acturally, when you using the org. NiCd battery holder from Metz, the "-" is in position 2 o´clock.

    Pls refer to my link

  3. Yes, that is exactly the purpose of the test.

    The Battery Holder is easier to use because you do not have to dismantle it to change the cells and you will not require a special charger.

    I really prefer my Anssmann Charger that detects flawed cells.

  4. it's really an amazing and helpful post,.
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  5. Keep posting more detailed and informative post about the batteries,..
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