Fill flash with MP/SF24D

[PATB]

I am thinking of getting an SF24D for my MP. While I try not to photograph in bad light, my kids do not wait for good light to do something fun that I want to capture on film. Last summer, I took pictures midday and found the shadows too contrasty.

So I am thinking of committing the ultimate Leica sin and use flash for fill. But I haven't used a non-TTL flash before. I'd appreciate any tips on how to use a flash with an MP, especially for fill.

Thanks much for any information you can send my way.

[ChadHahn]

One thing I learned was to meter for the bright light with the shutter speed being the flash sync speed. Then set the flash for the aperture. Fire away. The light and the shadows should be balanced.

Chad

[giordano]

IMHO the SF24D isn't powerful enough to make a versatile fill-in flash for a film M in daylight.

The problem is the antique 1/50 sec sync speed (20 milliseconds). This means that the flash, which lasts about 1 millisecond, has to put enough light onto the scene in that one millisecond to come within a stop or three of matching 20 milliseconds of the natural light.

Suppose you want the fill-in flash to be two stops below the natural light. That means that 1 millisecond of flash has to match 5 milliseconds of natural light: i.e. that the flash needs to be four times as bright as the natural light.

Indoors or in dim light this is no problem, but in midday daylight with deep shadows a little flash like the SF24D can only achieve it if the subject is quite close. An example with guide numbers makes this clear:

• Moderate sunlight. Film ISO 100. Shutter speed 1/50. Aperture is say f/16.
• With mid-range lenses the SF24D's official guide number is 20 metres at ISO100. This would give a maximum working distance at f/16 of 20/16 = 1.25 metres.
• To get fill-flash two stops below the natural light we can set the flash to A and tell it that the film is ISO 100 and the aperture f/8, or that the film is ISO400 and the aperture f/16. Either way the effect is to double the maximum working distance to 3.5 metres.

If 3.5 metres is enough for you then the SF24D should do what you need. I've always preferred to have some power in hand and for fill-in flash in daylight with a film M like to have a guide number of 45 or 60 metres at ISO100.

By the way, the question of fill-in flash power is independent of film speed and neutral density filters: it just depends on the ratio between the natural light in the exposure time and the burst of light from the flash. A Hasselblad with Compur shutter and 1/500 sync speed, or even a M8 with 1/250, get away with much less powerful fill-in flash units.

(I've no experience of focal plane shutters and flashguns with "high speed synchronisation", but as far as I can make out this is done by making the flash emit a much longer flash than usual, long enough to cover the entire period of the shutter's travel. That's fine as far as it goes, but the energy the flash can put out into one flash is limited by its capacitor, so you're just getting a longer-lasting but less bright light: so there's no advantage for fill-in flash. Please someone correct me if I'm wrong!)

[budrichard]

I have a SF 24D and don't even attempt fill flash with any M.
I have had Compur shutter equipment in the past for fill flash but now with the faster synch speeds of newer cameras along with thier dedicated flashes, i would look for a camera/flash that would do what i wanted.-Dick

[PATB]

Thank you for the replies. I am beginning to realize why M flash photography, especially with an MP, is not ideal.