So Shutter Speed is only for ambient light, not flash?

rgrebby

rgrebby

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Richard
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Is this totally true?

Maybe because my crappy bower flash is only ETTL and automatic nothing really changes?
 
With any flash in any mode, the shutter speed controls the ambient (continuous) light and the aperture controls the flash.

In other words, set the aperture to suit the flash power and the shutter speed to suit the ambient power.

Used in a studio situation, where the level of ambient light is too low to make any difference, you set the shutter speed to whatever will work on your camera (not more than 1/125th for safety).
 
All true. I mentioned this in a prior post but what I do is think of an image with flash as two separate exposures.

I set a combination of shutter speed /aperture for the ambient light. Rather than have this set correctly I underexpose by one or two stops. Then switch your flash to TTL and let it take care of the flash lit part of the subject. If you want or need to have your flash on manual power (for instance you may be using a radio trigger) then you can alter the brightness of the flash lit part of the scene by adjusting your aperture (remembering to compensate for the subsequent change in the ambient light level the adjustment will make).

Of course, changing aperture will have an effect on the appearance of the image so it may be more practical to either lower the flash output or physically moving the flash to change its power.

Sorry if this sounds complex but with a little practice it soons becomes pretty clear.
 
Wel, as I say, if depth of field is an issue at hand then you either lower the power output of the flash (for example my Speedlite 430 EX II has a six stop variable output) or move the flash closer to or further away from the subject.
 
subseasniper said:
Wel, as I say, if depth of field is an issue at hand then you either lower the power output of the flash (for example my Speedlite 430 EX II has a six stop variable output) or move the flash closer to or further away from the subject.
Click to expand...

Ahh ok, makes sense

Gary.
 
Don't forget, the flash has a "shutter speed" too.

Once you have your shutter speed in the camera matched to coincide witht he fastest fully open shutter duration....synch speed, then the camera shutter will only affect the natural light falling around - ambient.

The flash power (lets leave it set at the same power for now) will have a certain "reach" - the maximum at which it can illuminate the subject successfully. You have to set the flash power to match the aperture - or the aperture to match what the flash can achieve (so they need to be balanced, the flash power and aperture).

The flashes "shutter speed" I refer to is nothing to do with the actual shutter in the camera, but is the "freezing of motion" capability of the flash.....that burst of flash which illuminates your subject has a duration - depending on the power setting this can be anything from about 1/650th to 1/75,000th or even faSTER WITH SPECIALIST LIGHTING UNITS. (oops).

If you have a reasonable amount of ambient light, then you can still run into camera shake problems even when using flash, if you set too low a shutter speed for the length of your lens in use, by trying to get too much in focus (that big group at a dinner party for instance - f11, flash and the shutter to match is 1/2 sec or somehting) SO, something has to give - EITHER, you open your aperture up a good bit (f4 maybe) and put up with the depth of field achieved, OR you use a more powerful flash unit, or you could use a tripod and tell everyone they have ot keep still while the picture cooks......or you could wind up your ISO speed to give you more margin to work with at the expense of quality......it is all about compromise.

But in effect, it is only the aperture that controls flash lighting of the subject - provided you are within the synch speed of the camera. Anything below that will work - if you use too fast a shutter speed for the flash sycnh then you will get a dark section to your image. If your image simply comes out too dark - you don't have enough light, simple as that - your subject is too far away (or your gun is too weak) or you have used to small an aperture (too big an f number.....f4 is a bigger hole in the lens than f8)
 
With the light out....I did trip over myself a bit didn't I....too much gin tonight! Good shoot over in Essex - no, the WILDS of Essex....over 490 miles round trip and the shoot.....needed a gin - only 4 fingers. Twice.
 
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