flash SF20 auto mode

[findranger]

Advertisement (gone after registration)

Hej,

 

I am trying to get a grip on flash photography.

 

I use a Leicaflash SF20 with my Leica M4-P and Mamiya M7ii (great with its flash sync over the whole speedrange!). So manual and auto mode are my options here.

 

I get good and controllable results in the flash's MANUAL mode for fills etc.

 

But the AUTO mode is a mystery to me - results vary wildly. I understand that the flash will adjust its power depending on light conditions and ISO/aperture/EVcomp data (on the back of the body) to expose correctly.

 

What I don't understand: Which area is exactly measured by the flash and how can it know how far my subject matter is away from the camera/flash (very important due to the falloff of the flashlight)? Is it a bit of a lottery or am I not getting something here?

Also: flash's AUTO mode suffers from the same issues as camera's auto exposure modes, right (bright/dark backgrounds etc.)?

 

Thank you very much for clarification.

P.

[wattsy]

What I don't understand: Which area is exactly measured by the flash and how can it know how far my subject matter is away from the camera/flash (very important due to the falloff of the flashlight)? Is it a bit of a lottery or am I not getting something here?

 

The integrated light sensor is fairly crude and simply shuts the flash down when it has received the amount of light specified by the setting – it has no way of knowing what distance the subject is away from the camera. The measuring angle of the sensor is 25°. In my experience, auto-mode is a fairly reliable way of using flash if you use it like you would a camera with a very basic centre weighted meter.

Edited February 11, 2014 by wattsy

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[findranger]

So this is how I would try to get a proper fill light with little accentuated flash (camera mode all manual):

 

SF20 in manual mode:

- measuring scene for ambient and set camera's corresponding aperture and speed

- substract maybe 1 EV for ambient via camera's shutter speed (does't affect flash) to accentuate the fill flash

- set flash to cameras ISO and Aperture

- use power compensation button to set flash to correct subject distance

- reduce flash fill by 1 or 2 f-stops via power compensation or flash filter to avoid overexposure in combination with ambient light

 

SF20 in auto mode:

- measuring scene for ambient and set camera's corresponding aperture and speed

- substract maybe 1 EV for ambient via camera's shutter speed (does't affect flash).

- set flash to camera's aperture and film's ISO

- reduce flash fill by 1 or 2 f-stops via EV compensation button or flash filter or "wrong" ISO/aperture settings to avoid overexposure in combination with ambient light

 

Like this?

Thank you.

Edited February 11, 2014 by findranger

[M9reno]

I find Auto mode on the SF20 unpredictable (and I assume on the newer SF24 it would be exactly the same). I also find that the choice to adjust down EV is limited, from 0-3 EV at ISO values below 160, from 0-2 below 320, and 0-1 below 640. (This is not mentioned in the instruction manual, as far as I know). No ability to increase EV above zero.

 

Anyway, while in practice adjusting down EV will lower flash output, it still leaves the sensor at the front of the flash unit in control of the emission. Unpredictable, especially if you use film and can't see the result on the spot.

 

Much better to stick with Manual mode, I think.

 

To do fill flash, I do the following:

1. Measure the distance to the subject on the rangefinder. If the subject is staggered, from near to far, I usually measure to the nearest part of it, or at most the front third of it.

2. Set the camera speed dial to the fastest flash-sync time. 1/180 on the M9.

3. Adjust down the flash emission using the /P button. Each halving of the /P value is compensated by a slower shutter speed on the camera's speed dial. For example, if I set the flash at 1/4 power, I slow down the camera speed from 1/180 to 1/45.

4. Set the correct diaphragm/distance combination on the flash, and the corresponding aperture on the lens. If the distances available or the depth of field required are not what you want, go back to step 3 and change the flash emission (/P) value and shutter speed.

5. Lower speed on the camera even further, in my example from 1/45 to 1/15 or 1/8, to give more ambient light in low-light situations (usually indoors). Camera shake and motion are greatly reduced even at such speeds by the flash.

6. Shoot.

?

 

All the above assume shooting with the SF20 mounted on the camera, i.e. directly flashing the subject. Adjust as required if you are shooting bounce flash with a cord.

 

Major caveat to the OP: I am myself just a beginner with flash. The advice should thus be taken with the question mark at the end. I will also be interested to hear what other members think of this method.

 

Thanks.