Strobes

[showtm490]

I'm using a Rebel XT with Cactus V2s and Sunpack 383's all on manual. When I drop my shutter speed it doesn't allow more light to come in. At 30 I get the same effect as at 200. The only way to get more light is by bumping up my ISO. Why is the shutter speed not making any effects?

[cyclohexane]

Flash exposure is controlled by your aperture and the duration of the flash.

Your shutter speed is inconsequential to the flash exposure; it will affect your ambient light exposure, but if the flash output remains constant you will not see a change in your flash exposure by lowering the shutter speed.

[Songman45]

What is the lighting like aside from the flash. There may not be an appreciable amouont of ambiant light to impact the image. Try exposing the image without the flash at both shutter speeds and take a look at what is being contributed to the exposure other than than the flash.

[showtm490]

I used natural morning light for an outside shot and I used a florecent light above the model on an inside shot. When no strobes are used the shutter speed works like normal but I used the strobes th highlight shadows.

[Songman45]

Originally Posted by cyclohexane

Flash exposure is controlled by your aperture and the duration of the flash.

Your shutter speed is inconsequential to the flash exposure; it will affect your ambient light exposure, but if the flash output remains constant you will not see a change in your flash exposure by lowering the shutter speed.

Unless, of course the ambiant light is greater than the output of the flash. In which case dragging the shutter will have an impact.

[showtm490]

I'm going to play with it more tomorrow. Quick question, on the strobe I can set the ISO. Should it be set the same as the camera or does it not matter?

[00silvergt]

Originally Posted by showtm490

I'm going to play with it more tomorrow. Quick question, on the strobe I can set the ISO. Should it be set the same as the camera or does it not matter?

You shouldn't be setting anything on the strobe, if you are using it in manual mode. If you are using automatic or ETTL or iTTL the electronics will compensate for the exposure you set by varying the strength of the flash if possible.(depending on your exposure mode on the dial, with Canon, in Av mode, the flash is set to properly expose the foreground, while it uses the normal metered exposure to properly expose the background.)

I manual mode you will be simply "dialing" the strength of the flash and the duration, with Canon it is done in fractions 1/1, 1/2, 1/4, and so on.