Quick external flash question...

i8urjeep · Sep 1, 2006

How do i use it!! I have a canon 10d, and a canon speedlight 380ex.
Do i just stick the flash on the hot shoe, turn it on and start shooting normally? Do i need to adjust for exposure using a flash?

I'm so confused that i'm embarrassed posting this question.

Thank you guys in advance for helping me.

JamesD · Sep 1, 2006

The general advice is this:

Divide the guide number of the flash by the distance to your subject. The resulting number is the aperture you should use to properly expose your subject AT ISO 100.

For each stop of ISO above 100 add one f/stop of aperture. So, for instance, if you should use F/8 at iso 100, then at 200, 400, and 800, you would use F/11, F/16, and F/22 respectively. Vice versa if you use ISO 50, 25, etc.

When using flash, aperture controls flash exposure, while shutter speed controls exposure for ambient light. Getting the flash to ambient ratio right takes some practice, but if you're shooting digital, it shouldn't be difficult since you can see the results immediately.

With film it's a bit trickier. Someone else can probably help you better than I can, since I haven't much experience with flash. I typically use available light, or add continuous light.

Good luck!

EDIT: BTW, be sure that you use the right guide number. It varies with the flash zoom setting, and also make sure you use the GN for meters if you're measuring distance in meteres, but use the GN for feet if you're measuring feet. ;-)

i8urjeep · Sep 1, 2006

Thank you so much for your reply.

What is a guide number? (you mean, the number 380?) Excuse my ignorance on this subject, it's the only thing i'm having a hard time with. I typically only use natural lighting as well (and it's my preference) but i have some situations coming up to where i'll need to use this flash. I'm so nervous and scared. I'm shooting raw, but still want to get it right and to be educated on this. I'm trying to find things online to look up but i cannot get straight answer from the net (which is why i'm here)

So, what's the guide number again?

JamesD · Sep 1, 2006

The best option is to consult the manual. However, if you don't have it...

the guide number should be 38 with the flash zoom set to 105mm (which is what you'd use with a 105mm lens on your camera). This guide number is for meters. So, if your subject is 5 meters away, you'd want to use an aperture number 38 / 5 = 7.6, so about f/8 if you're using a 105mm lens and ISO 100 film (or the ISO 100 setting on a digital). If you want to work with feet instead of meters, just multiply the guide number by 3.

This page may be of some help: http://photonotes.org/cgi-bin/flash-specs.pl?flashType=canon380ex

It's not as scary as it sounds at first. Try it out, and look at your results. That's one great thing about digital... you can see the results right away and make adjustments.

Remember this: if the subject is too dark or too light, change your aperture to fix it (higher f-number to darken, lower the f-number to lighten). If the surroundings are too dark or too light, change your shutter speed (faster shutter speed to darken, longer shutter speed to lighten). Try it!

If you can, try moving the flash off the camera, or point it up at the ceiling. On-camera flash is generally a little bad for the image (deer in the headlights, red-eye, flat contrast, etc). If you bounce the flash at the ceiling, you'll have to adjust your exposure accordingly.

The best advice I can give you is to play with it. Experiment until you find a technique that works for you, then work with that.

Good luck!

i8urjeep · Sep 1, 2006

You're amazing, thank you!
I will experiment with what you mentioned tonight.

Thanks again.

JIP · Sep 1, 2006

The most smple way to do what you want is just set your camera to whatever you normally use and set the flash to TTL and let the camera do the rest the only setting you dont want to use TTL flash on is shutter priority. The 380ex being a Canon dedicated flash the flas and camera work together.