SF24D flash tutorial for non-TTL M

[wide.angle]

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Ok, I've got an MP and am in the process of learning to use the SF24D with this. Thus, TTL is not available for this camera of course, so I have A mode and M modes available.

 

I would like first to master the A mode, which means the flash unit will be calculating its own exposure based on the film speed and aperture selected.

 

Now I could eliminate the ambient light in subdued situtations, by setting the camera to its synch speed, then using a high number f stop then setting the flash to match film speed and f-stop, from that I would likely get a proper exposure using only flash light. However, I would like to learn to balance ambient and flash light for "proper" exposure.

 

To assist in learning, allow me to describe a scenario. Ambient light provides a proper exposure at f/4 for 1/15 sec at ISO 200 (and if needed subject is 8 feet away and using a 35mm lens). For purposes of this, also assume that the flash, if off camera (e.g., to right of camera facing subject) is at the same distance from the subject as the camera.

 

For the above situation, can someone explain how I might adjust the camera settings (if at all) and set the flash in A mode for the following two scenarios?

 

Scenario 1: use ambient as main light source, and flash as fill.

 

Scenario 2: use flash as main light source, and ambient as fill.

 

The information I have found on the web seems mostly geared for digital cameras now, and explains how to ratio the lighting by using the camera histogram.

[moikle]

I am not fully conversant with the MP as I use an M7 but, I do not understand why you do not have TTL available?

 

Mike

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[wide.angle]

Mike, although the MP has TTL metering for exposure, unlike the M7 it does not have TTL flash control so the flash needs to figure it out on its own or be set manually.

[mschlapfer]

Answer to scenario 2 first:

1. Aperture of f/4 is chosen and set on both camera and flash.

2. Shutter speed is set to 1/15 for proper ambient exposure.(The flash doesn't care about the shutter speed, it's exposure is determined by the aperture).

3. ISO 200 is set on the flash in AUTO which should render a proper flash exposure providing f/4 setting was also chosen and subject is within flash's output range.

4. This would answer scenario 2 as flash as main with ambient as fill. In theory this would be pretty much a 1 to 1 ratio.

Note: Dial in faster shutter speeds up to maximum sync speed to"darken" the ambient fill.

 

Answer to scenario 1:

1. Camera set to f/4 @ 1/15 ISO 200

2. Still using AUTO mode on the flash...either tell the flash f/2.8 (or f/2 if you like). Flash will assume larger aperture on camera and adjust (lessen) it's output accordingly, or....

3. Set the flash's ISO to a higher number (ie: 400 for 1 stop difference) and again the the flash will lessen it's output.

Note: One could combine options 2 and 3 to create different ratios.

4. Voila! Fill flash.

[wide.angle]

Thanks Michael. The setup you outlined is very straight forward.

 

The only thing that confuses me is why they do not lead to overexposures since the camera is set for exposure from one light source, then additional light is let in from the second source.

[mschlapfer]

The only thing that confuses me is why they do not lead to overexposures since the camera is set for exposure from one light source, then additional light is let in from the second source.

 

1st point to remember is the "flash exposure" component of the overall exposure is determined solely by the lens aperture chosen.

 

Since we are talking about working with an "old fashioned" AUTO flash, it's settings and sensor are the keys.

 

In your scenario, you've described a properly metered ambient scene.(You know what you should get there).

 

Just shooting as I described in scenario 2 is pretty much what the flash was designed to do, assuming you the photgrapher work within it's parameters. (1 to 1 ratio).

From that point it's up to you to decide whether you want an "imbalanced" exposure.

As described earlier, there are a few ways to get there, depending on the look you are after.

 

But to answer your question, assuming the f/4 @ 1/15 is the proper ambient exposure and you have in fact set the flash properly for it's part of the exposure, at this point you are reliant on that AUTO sensor getting it "correct" to properly adjust the flash output. I don't know any other way of phrasing this. The combining of two light sources don't lead to overexposure because you are "controlling" both of them. But until the flash fires, you are only seeing one of the sources. Gotta have faith in the fact you have controlled that second source : )

TTL flash obviously simplified so much of this, but to be honest, I feel I get more predictable results working the way we are talking about here.

FWIW, I too have an MP but I don't own the SF24D. But I am going on the assumption that the SF24D with it's AUTO sensor is meant to function like virtually all other AUTO sensor flashes.

[moikle]

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Mike, although the MP has TTL metering for exposure, unlike the M7 it does not have TTL flash control.

 

I did say I was not fully conversant with the MP. I was not aware that it does not have TTL flash. Another thing learned :-)

 

Mike