Flash on manual

[michaelachan]

Hi guys,

I've been using my flashgun alot in low light situations in my house. Usually I bounce the flash off the ceiling. However I can't get my head around using my flashgun on manual.

I know a fair amount about digital photography, but Im getting really confused about its settings on Manual. So I have a 580ex speedlite and I changed the custom function to manual. I adjust my ISO and Aperture to correspond to the camera settings.... my question is.. what shutterspeed do I use? I've read my camera and flash manual a numerous amount of times now, but unlike the universal flashguns at my college which I thoroughly understand - I am extremely confused! Help

Somebody told me to use any shutterspeed below 1/125 ... but why? I'd like to know the theory behind it, rather than just using these settings that work without knowing how it works..

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UPDATE

Ok so I've just been playing around with my flash at different shutter speed increments of 4, 10, 25, 50, 125 of a second. What I noticed in doing so, is that a slower shutter speed brought out the background where as a faster shutter speed didn't light up much of the background (obviously) this is having my flash at a 90 degree angle.

I am trying to produce the same outcome that I can on auto, in manual so that I can understand how it works, but Im not getting the same results. I've set my ISO to 100 and aperture at 5.6

[thazooo]

All flashes have a guide number, you should be able to do a search for a chart that will give you shutter vs. aperture vs. distance. Your flash should also operate just like the universal flash guns when put it in manual.

Using shutter speed you'll see little changes in the light, using aperture
you'll see greater changes.

[dougj]

The flash is frequently the primary source of light, and the duration of the flash is limited. Hence setting the SS to 1/125 or 1/8 has little effect on the final exposure as long as it is at least equal to the flash duration. This assumes there is very little ambient light and all other settings are the same.

Increasing the exposure time uses more of the ambient light present, and helps eliminate the 'flatness' and reduce the black background of flash-only lighting. This is frequently called 'dragging the shutter', here is a good article with some examples.

http://planetneil.com/tangents/flash-ph ... e-shutter/

I suggest you start at the first part of the complete article, there are some good tips, explanations & examples of various flash techniques.

[ernst]

If you're using flash, for a given flash output the exposure is only controlled by the aperture of the camera lens. A larger aperture yields a brighter image.
As you already discovered, shutter speed controls the ambient light of the background.
You should keep the shutter speed at 1/250 s or longer, because at faster speeds the shutter doesn't open completely, with only partly exposed pictures as result. This is the synchronisation speed, which depends on camera make and model, but is probably 1/200 s. For older cameras it is probably 1/60 s.

I find http://www.strobist.com a great site to learn about flash lighting. Go for the archives and find "Lighting 101", which tells you everything you need to know for a thorough start in flash lighting.

For manual settings of the 580, just push the Mode button until "M" is shown in the display. You can then adjust the output power with the dial wheel. No custom functions necessary...

Good luck!