Meter & exposure with speedlite 430

[Ricky21]

So I've been shooting in M a lot lately and really getting goodie results. (sharp and nicely exposed photos). I have has some issues with deterring proper exposure using the meter while using a flash. For example, I was shooting my son opening some presents yesterday at his bday party and the meter shows a couple increments underexposed when activated, but when I shoot photo its properly exposed due to external flash.

My question is how so I determine proper exposure prior to the shot with an external flash? I know there is a pilot button that fires a quick burst but I'm not sure that is enough time to determine proper exposure.

Is there a technique to this?

 

[MTVision]

I'm pretty sure the in-camera meter is useless when using flash.

Are you using the flash in manual or iTTL (or whatever is called)? Are you setting the flash output?

 

[tirediron]

If you're shooting with the flash in e-TTL mode, don't worry about it; it will take care of the exposure on it's own. If you want to shoot manual flash you have three options. Guess, shoot, review, or use the flashe's GN to calculate exposure (scroll part-way down the page for the paragraph on that), or buy a flash meter.

 

[Ricky21]

If you're shooting with the flash in e-TTL mode, don't worry about it; it will take care of the exposure on it's own. If you want to shoot manual flash you have three options. Guess, shoot, review, or use the flashe's GN to calculate exposure (scroll part-way down the page for the paragraph on that), or buy a flash meter.

Yes, I'm shooting in E-TTL mode. So, I should set up the photo with the ISO/shutter speed/aperture that will produce the look I'm going for and let the E-TTL flash mode properly expose the image? Or, do I need to take the original camera metering into consideration before relying on the flash to provide enough light for proper exposure?

 

[Big Mike]

The in-camera meter isn't useless...but it doesn't take the flash into account. In other words, it's giving you a reading of the reflected ambient light.

If you are using the flash in E-TTL (auto metering) mode, then the flash will use a pre-flash, right before the shutter opens, to determine how much power it will need. It will take into account the aperture and ISO setting on the camera, as those will affect how much output the flash will need to use. (shutter speed doesn't affect flash exposure).

E-TTL metering works very much like 'regular' metering....it is calibrated to give proper exposure for a subject/scene that is middle grey. So if your subject isn't middle grey, then the resulting photo probably won't have accurate exposure.
This is where you can use FEC (flash exposure compensation). This will tell the E-TTL system to give you more or less flash exposure...but it's still based on what you're shooting each shot.

Another alternative would be to put the flash into manual mode as well. The flash has a distance reading when in manual mode...and that tells you at what distance you'll get proper exposure. It work pretty well, but you have to be good at estimating distance, if you don't want to measure each time. You can still use this method when bouncing the flash off of walls or the ceiling, but you have to account for absorption, so the calculation can get complicated.

Here's a popular way to shoot with flash. Camera in manual, flash in E-TTL. You set your aperture for the DOF that you want (keeping in mind that a larger aperture means less power required from the flash). You set your shutter speed for the ambient exposure that you want...using it to control the balance between ambient and flash exposure. You set your ISO to help control the ambient exposure, also keeping in mind that a higher ISO will require less light from the flash.

So as you're adjusting your settings, keep an eye on the in-camera meter/scale. The closer you are to zero, the more likely you are to get an even balance of flash and ambient. Of course, in many situations, this would require a shutter speed that is too long for your liking (would cause blur)....so you either increase your ISO, or you just let the needle fall below the zero. That would cause your ambient exposure (often the background) to be darker than the flash exposure (usually your foreground or subject). It's common to purposely underexpose the background by a stop or so, then use the flash to light up the subject.
You may have to adjust your FEC, depending on how bright/reflective your subject is. With digital, it's easy enough to take a shot, check it quickly and adjust if needed.