Studying old electronic flash

kl122002 · Jun 5, 2023

While I was working on my Metz 60 CT-4, I have taken some time to study older electronic flash (back to 1950s ). Suprising I noticed their Guide Numbers (GN) is very different from today's standard. They are not just show for feet and meter, but also in different film speed and type .

For example , the Ultrablitz Cornet L has GN spec like this :
92...105 B&W (17 DIN / 40 ASA)
46...53 Colour (18 DIN / 50ASA)

That's way lot brighter than my 60 CT-4 ? And it is just using 3.6V NiCd internal battery ?

Chan Tran · Jun 5, 2023

If they are in meter and not in feet. The Metz 60 would have the GN of 42 for ISO 50 in meters. What doesn't make sense that why the GN is higher for ASA40 than ASA50?

Dennis-B · Jun 5, 2023

Take those old "guide numbers" with a grain of salt. Most were notoriously overstated. However, print film has always had a lot of latitude on both sides of the guide number. The makers also used their own "standards" for output.

As electronic flashes modernized, got newer circuitry (Thyristor, e.g.), the numbers became a bit more realistic. Finally, guide numbers more or less settled on ISO 100 as the "standard"; you can adjust from that point, up or down.

I owned Honeywell Strobonars for years, and they advertised a K2 (ISO 25) guide number of 80. However, even that was overly optimistic based on experimentation with transparency film, which is far more unforgiving.

The real test is to used a good flash meter. Even the older Wein models were good. I finally standardized with the Minolta Autometer IV. With the advent of TTL flash metering, the older methods of guide numbers became somewhat moot.

Chan Tran · Jun 5, 2023

All flashes I have ever tested had their GN inflated. I read somewhere a document from Metz but I can't find it any more that Metz use a 50% reflectance surface to determine GN. The GN method is of little used as it doesn't work when you use bounce flash.

kl122002 · Jun 7, 2023

Dennis-B said:
Take those old "guide numbers" with a grain of salt. Most were notoriously overstated. However, print film has always had a lot of latitude on both sides of the guide number. The makers also used their own "standards" for output.

As electronic flashes modernized, got newer circuitry (Thyristor, e.g.), the numbers became a bit more realistic. Finally, guide numbers more or less settled on ISO 100 as the "standard"; you can adjust from that point, up or down.

I owned Honeywell Strobonars for years, and they advertised a K2 (ISO 25) guide number of 80. However, even that was overly optimistic based on experimentation with transparency film, which is far more unforgiving.

The real test is to used a good flash meter. Even the older Wein models were good. I finally standardized with the Minolta Autometer IV. With the advent of TTL flash metering, the older methods of guide numbers became somewhat moot.

I still work on the GNs back when I was learning photography. TTL and E-TTL have saved me a lot of calculation, but it seems I still do the old way. Looks like that has been part of me.

kl122002 · Jun 10, 2023

I just learnt some old flashs are using either old Wet cells or dry cells . While some, like Metz Mecablitz 32 (from 1950s) is able to use either one too! And that comes the question,

I know wet cells are actually lead-acid cells, as for Metz Mecablitz 32 is like using a 4V 3Ah wet cell , while for dry cell compatable models is use 4 x 1.5 D-cells in series connection. But that is strange, since the serial D-cells is giving a 6V, but that is real contrast to wet cell with 4V /3Ah . Why ? And from the old manuals I can see the Wet cells can give more flashes?

And if I deceided to restore a old flash like this, does it mean I can actually connect the original wet cells wires to a 18650 cell and bring the old flash back to work ? (Of course I won't use the flash to charge up the modern 18650 cell )

Chan Tran · Jun 10, 2023

kl122002 said:
I just learnt some old flashs are using either old Wet cells or dry cells . While some, like Metz Mecablitz 32 (from 1950s) is able to use either one too! And that comes the question,I thin

I know wet cells are actually lead-acid cells, as for Metz Mecablitz 32 is like using a 4V 3Ah wet cell , while for dry cell compatable models is use 4 x 1.5 D-cells in series connection. But that is strange, since the serial D-cells is giving a 6V, but that is real contrast to wet cell with 4V /3Ah . Why ? And from the old manuals I can see the Wet cells can give more flashes?

And if I deceided to restore a old flash like this, does it mean I can actually connect the original wet cells wires to a 18650 cell and bring the old flash back to work ? (Of course I won't use the flash to charge up the modern 18650 cell )

I think the problem of using Li-Ion to replace lead acid is one of mismatch voltage. 1 Li-Ion cell voltage is from 4.2 to 3.7V between full charged and needs to charge while close the lead acid of about 4.2 to 4V. But the lead acid battery would stay at or above 4V for it's useful cycle while the Li-Ion would be less than 4V for most of the discharge cycle closer to the 3.7V most of the time.

Ian C · Jun 10, 2023

The environment in which a flash is tested has a significant effect on the measurment. Indoor readings are generally greater due to the reflectance of floor, walls, ceilings, and so forth. The greatest inflation of the measurement happens with a light colored floor with white walls and ceiling. This is particularly problematic in small rooms with low ceilings.

I test flash outdoors at night away from any reflective surfaces. Flash tested in this way gives a reasonably accurate measurement of the light output of the flash unit without the reflectance of surfaces inflating the results.

To learn the effective guide number of a flash in the particular environment in which is to be used, the measurement has to be done in that environment. Of course, if you have an accurate flash meter at hand, you don’t actually need the guide number.

kl122002 · Jun 10, 2023

Chan Tran said:
I think the problem of using Li-Ion to replace lead acid is one of mismatch voltage. 1 Li-Ion cell voltage is from 4.2 to 3.7V between full charged and needs to charge while close the lead acid of about 4.2 to 4V. But the lead acid battery would stay at or above 4V for it's useful cycle while the Li-Ion would be less than 4V for most of the discharge cycle closer to the 3.7V most of the time.

Agree. But how about for those has switchable sources, like either Dry cells (D-cells) or Wet cells ? If the flash can be operated either 6V (from 4 x D cells) or 4V from a Wet cell, should I say it's working voltage is in-between 4-6V?

Chan Tran · Jun 10, 2023

kl122002 said:
Agree. But how about for those has switchable sources, like either Dry cells (D-cells) or Wet cells ? If the flash can be operated either 6V (from 4 x D cells) or 4V from a Wet cell, should I say it's working voltage is in-between 4-6V?

You have to study the circuit to allow them to switch between battery type. The Metz 60 power pack has the settings but only for the charging circuit.

kl122002 · Jun 10, 2023

Chan Tran said:
You have to study the circuit to allow them to switch between battery type. The Metz 60 power pack has the settings but only for the charging circuit.

I am not talking about the modern 60 CT, but old flashes like Mecablitz 32 made in 1950s.

Mecablitz 32 – Olypedia

olypedia.de

Chan Tran · Jun 10, 2023

kl122002 said:
I am not talking about the modern 60 CT, but old flashes like Mecablitz 32 made in 1950s.

Mecablitz 32 – Olypedia

olypedia.de

That's what I meant. You have to study the circuit. I don't have the 32. I have the 60 and I studied it and found the settings is only for charging circuit.

kl122002 · Jun 10, 2023

Chan Tran said:
That's what I meant. You have to study the circuit. I don't have the 32. I have the 60 and I studied it and found the settings is only for charging circuit.

Just as as I could tell, from referring to a higher power model Mecablitz 500 or Mecablitz 50, The power pack could offer charing to wet cell also AC powered flash . Mecablitz 32 is also the same but also added D-cell power support.

Perhaps I would get one and see what it could do.

Chan Tran · Jun 11, 2023

kl122002 said:
Just as as I could tell, from referring to a higher power model Mecablitz 500 or Mecablitz 50, The power pack could offer charing to wet cell also AC powered flash . Mecablitz 32 is also the same but also added D-cell power support.

Perhaps I would get one and see what it could do.

I would try to use a power supply to power it via the battery connection. I would start with the power supply set at 4V and limit the current to 2A or so. Then if the flash recycle too slowly I would increase the current limit up. I don't think you would need to go more than 5A. If you power it with a battery with high current capacity it may pull too much current and got damaged. After that I would adjust the voltage lower and higher a bit to see how it perform.
I have tried running my Metz 60 with 4 18650 Li-Ion. Paralell 2 groups of 2 in series. to give 7.2 to 8.4V and it works well but I think it does stress the flash .

kl122002 · Jun 11, 2023

Chan Tran said:
I would try to use a power supply to power it via the battery connection. I would start with the power supply set at 4V and limit the current to 2A or so. Then if the flash recycle too slowly I would increase the current limit up. I don't think you would need to go more than 5A. If you power it with a battery with high current capacity it may pull too much current and got damaged. After that I would adjust the voltage lower and higher a bit to see how it perform.
I have tried running my Metz 60 with 4 18650 Li-Ion. Paralell 2 groups of 2 in series. to give 7.2 to 8.4V and it works well but I think it does stress the flash .

Thanks for the suggestion .
Just ordering one from ebay and it looks ok inside . Waiting for the shippment from Germany and now I crossing my fingers hoping ti will come safely

I don't think Metz 60 could work with 18650. The problem is the voltage from 2 x 1860 is too high (7.2V) . Back in the days I have seen people modify their Metz 60 powper pack for faster recharge , but the high voltage brings worng reading to the built-in sensor and giving the wrong flash output. So 6V should be 6V , or not too much over or under that that should be the safetiest operating voltage.

I found Mecablitz 500 's repair manual here , we can see how the wet cell works in this old flash:

https://www.cameramanuals.org/flashes_meters/mecablitz_500_service.pdf

Chan Tran · Jun 11, 2023

kl122002 said:
Thanks for the suggestion .
Just ordering one from ebay and it looks ok inside . Waiting for the shippment from Germany and now I crossing my fingers hoping ti will come safely

I don't think Metz 60 could work with 18650. The problem is the voltage from 2 x 1860 is too high (7.2V) . Back in the days I have seen people modify their Metz 60 powper pack for faster recharge , but the high voltage brings worng reading to the built-in sensor and giving the wrong flash output. So 6V should be 6V , or not too much over or under that that should be the safetiest operating voltage.

I found Mecablitz 500 's repair manual here , we can see how the wet cell works in this old flash:

https://www.cameramanuals.org/flashes_meters/mecablitz_500_service.pdf

My 60CT4 works fine with 18650 batteries. I tested light output both manual and auto with flash meters and there is no difference. The recycling time is faster than dryfit and the current draw is quite high somewhat higher than 5A when the capacitor is emty. When the capacitor is full it shut off for a little bit and the turn back on again.
I now power it with 2 LiFePo4 batteries which give 6.4V very close to the dryfit 6.3V. Also the LiFePo4 has very low self discharge rate better than Li-Ion.

Chan Tran · Jun 11, 2023

Looking at the capacitor size and voltage it's about 50W/s power.

kl122002 · Jun 11, 2023

Chan Tran said:
My 60CT4 works fine with 18650 batteries. I tested light output both manual and auto with flash meters and there is no difference. The recycling time is faster than dryfit and the current draw is quite high somewhat higher than 5A when the capacitor is emty. When the capacitor is full it shut off for a little bit and the turn back on again.
I now power it with 2 LiFePo4 batteries which give 6.4V very close to the dryfit 6.3V. Also the LiFePo4 has very low self discharge rate better than Li-Ion.

I have seen people using DIY high voltage supply on Metz 60 series and that burn the flash in the past. And that's why I tend to stay out from over powering it. I checked my local market twice, people here don't have the 32700 batteries and the LiFePo4 batteries is rare here. So I think I would stay with NiMH batteries.

Studying old electronic flash

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