A versus M in flash photography

I shoot primarily in manual when shooting flash photography on land and underwater. I understand how A priority works using fill flash - the same way it does when shooting with no flash. What I don't understand is how it selects the ss when using the flash as the primary source of light. In this scenario, the ss only serves to affect background exposure, so how can the camera make that decision? I know that a lot of Nikonos and film SLR shooters use this mode most of the time, so maybe someone can explain to me the advantage over selecting the ss manually.

Thanks

With Nikon cameras, you set the flash sync mode.

1) Set to normal sync, when in A mode and flash attached and powered, the camera will select the commensurate shutter speed based on you meter, but will default to 1/60 as a the minimum. You set/adjust the aperture. This eliminates motion blur in the unlit areas and creates black backgrounds (underexposure) at smaller f stops.

2) Set flash to slow sync when in A mode and the camera will adjust to any shutter speed commensurate with the selected aperture and metering mode.

I prefer manual for wide angle. I set shutter speed to 1/60 to eliminate motion blur (1/30 is often iffy). I then spot meter the background to get the ambient exposure to set aperture. This isn't any different than 2) expect that if the ambient exposure would yield a faster than 1/60 exposure, I can quickly stop down, which is what I usually want to do.

It comes down to what you are used to and comfortable with.

When you shoot the camera in M and the flash in M you aren't using any of the meters in the camera at all when you take the shot.

You may use the exposure meter to meter the blue background, but after that, nothing.

So when you go to A you kick in the exposure meter(s) One or more depending on whether you are in spot, CW, or Matrix. These meters will be used to set the shutter speed if you are in A. I find that as a general rule my S2 in matrix metering gives me a lighter blue background than I want, so I set -.5 stops of underexposure.

Normal flash minimum 1/60th speed. Slow or Slow/Rear will give you any shutter speed to get a "good" background exposure.

These meters have nothing to do w/ the flash. Those are controlled by the flash meters which are separate. There is a mode called "multi-sensor balanced fill flash" on the D100 that is similar to slow sync in that it is supposed to provide a "balanced" exposure w/ fill flash. But that isn't going to work underwater w/ the D100 and no D-TTL, and it won't work with the housed SB80 either because it isn't wide enough for WA anyways...

Cheers

James

When you shoot the camera in M and the flash in M you aren't using any of the meters in the camera at all when you take the shot.

That's a tad confusing. In M it doesn't use the meter to set any exposure parameters such as shutter speed or aperture. The meter still works. The viewfinder shows you how your manual settings will likely work based on your metering mode. You then adjust something until it gets you the exposure you want.

There is a mode called "multi-sensor balanced fill flash" on the D100 that is similar to slow sync in that it is supposed to provide a "balanced" exposure w/ fill flash. But that isn't going to work underwater w/ the D100 and no D-TTL, and it won't work with the housed SB80 either because it isn't wide enough for WA anyways...

I'm not sure how you equate multi-sensor balanced fill flash to slow sync. These are separate issues and settings.

The SB80 with diffuser on will cover 20mm. With strobofoam it covers 14mm, although I don't think the housings will allow its use. However, I do think the SB80 will not provide near enough light when diffused underwater.

Yes George. I don't have the skills to explain it here on a message board.

For a good explanation, take a look at Thom Hogan's Nikon Flash Guide folks. I've got a copy I can bring to the next HUPS meetintg if anyone's interested (Sorry Kasey, I know you can't make it...:-)

Cheers

James