Calculating manual flash powers without a flash meter - and other flash questions

[Overread]

Ok so I've got a medium format camera and I've got a flash. Now I want to combine the two of them to aid in lighting my subjects, however whilst I know that the ideal approach is to use a flash meter to measure the lighting at the subject this simply is not possible (no funds left for a flash meter!).

So I'm wondering if there is a way I can calculate a rough estimation of the flash power output needed to illuminate a subject without having to waste a lot of film shots bracketing a series of power levels (which in the end might or might not be enough/too much).

At the moment the best I can think of is to use my regular DSLR in a similar position and frame to the fullframe, meter the scene with it and then apply flash in manual power outputs until the exposure is sound on the DSLR and then simply use that flash power output (keeping distance equal at all times) for the medium format shot. However I'm wondering if there are any general inconsistencies that might arise and would necessitate either some form of compensation to the flash output value or bracketing to ensure a range of powers are covered.



In addition anyone know the proper name for the PC cord connection point on the Mamiya lenses themselves that allows connection to a regular DSLR; thus far all I have is a PC cord with a screwthread attachment and whilst it works it has no hold inside the slot on the lens and thus is very easily knocked out.

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[tirediron]

Easy-peasy for single flash: Aperture = GN/Dis so, let's say your flash has a GN of 50, and you're 10' from the subject, then, Aperture = 50/10, therefore aperture = f5; f5.6 should be close. Note: If you're shooting at a different ISO/ASA than your GN is based on (and most are based on ISO/ASA 100) than you will have to adjust accordingly.

I assume you're using a lens with a leaf shutter? AFAIK, that's just a standard PC socket. Sync cords coming out is/was a common problem. Hence the reason I always have a handful of elastic bands in my bag.

[compur]

Every flash has a guide number (GN) which is a measure of its light output and which can be used to determine correct exposure.

(The GN is usually given with the assumption of the usage of ISO 100 film and the distance-to-subject in feet but some flash units use some other ISO rating and/or distance in meters)

In short, GN = distance times f-stop number

So, with a GN of, say 40, and a distance of 10 feet you would use an aperture of f/4 because

40 = 10 X 4

More info here.

The above assumes you are using one flash only for your illumination. If you use more than one flash and/or combine flash with ambient light it gets more complicated.

[Big Mike]

As mentioned, the old 'manual' way of figuring out flash is to use the GN.

And yes, the PC connection is terrible and prone to coming loose. You can get 'screw lock' PC cables if it's a problem.

[ChristopherCoy]

The above assumes you are using one flash only for your illumination. If you use more than one flash and/or combine flash with ambient light it gets more complicated.

Do you think you could possibly give us a quick explanation using the 'big crayons'?

[Derrel]

I believe the PC connection's proper name is Prontor-Compur connection, named after two popular shutters from days of yore.

I was told when growing up, by a very old photographer, that "PC" stood for Poor Connection, and was short for PPC or Pi$$-poor Connection.

One handy tool to own is a PC tip conditioner, which keeps the tip of the PC cord "squished" to just the right tension, so that it fits tightly. The last one I saw was priced at $16.

[ChristopherCoy]

I believe the PC connection's proper name is Prontor-Compur connection, named after two popular shutters from days of yore.

From the Rollei's?

[Derrel]

I believe the PC connection's proper name is Prontor-Compur connection, named after two popular shutters from days of yore.

From the Rollei's?

Maybe so,I couldn't really say with ANY degree of certainty. A real camera collector and camera history buff, like TPF's very own member compur, would probably be able to tell us.

The Rolleiflex was invented right around the time of the flashbulb. As I recall, the flashbulb was invented in 1928 or '29, and the Rolleiflex TLR right around the same time, like one year earlier. But I am not certain that the PC connector was the first connector protocol used on Rollei's; there have been "other styles" of connectors used over the years, but the PC style did eventually win out over other connector styles.

[compur]

The above assumes you are using one flash only for your illumination. If you use more than one flash and/or combine flash with ambient light it gets more complicated.

Do you think you could possibly give us a quick explanation using the 'big crayons'?

It's not a big crayon topic. Entire books have been written about the subject. I suggest getting one. They're very inexpensive these days.

[compur]

I believe the PC connection's proper name is Prontor-Compur connection, named after two popular shutters from days of yore.

From the Rollei's?

Maybe so,I couldn't really say with ANY degree of certainty. A real camera collector and camera history buff, like TPF's very own member compur, would probably be able to tell us.

No one can even agree on which camera first had flash sync capability (some say Exakta, Kodak, Agfa, etc) so naming the first one with a PC socket would be tough. The PC socket evolved from earlier sockets that looked very similar but were not compatible. Zeiss started using actual PC connectors in the early 1950s so I would guess it was an Ikonta or Super Ikonta that had that honor but Rollei may have beaten them to it. Since the PC socket is really part of the shutter and the shutters weren't made by the camera manufacturer, it's really hard to pin down because both Prontor and Compur shutters were used by so many different cameras from different manufacturers. And many of them had various lens/shutter options on their different camera models to boot. I don't think anyone alive knows which one had the first actual PC connector.