430ex and Metering

[jonnahalf80]

When shooting without flash with my XTi, I am always refering to the Exposure Level in the viewfinder to know how exposed the picture would be with the current settings. However, and while indoor using the 430ex, the Exposure Level indicator is always at the far left, suggesting an underexposed image. Of course, when the flash fires, the picture is not as underexposed as the Exposure Level indicates.

I was wondering about how I could manually set the aperture/shutter speed, while using the flash to produce well exposed photos.

[noyjimi]

When shooting without flash with my XTi, I am always refering to the Exposure Level in the viewfinder to know how exposed the picture would be with the current settings. However, and while indoor using the 430ex, the Exposure Level indicator is always at the far left, suggesting an underexposed image.

Just to be sure, the indicator is not connected to your flash in any way. Your camera is metering the scene as it is (lit by ambient light).



Of course, when the flash fires, the picture is not as underexposed as the Exposure Level indicates. I was wondering about how I could manually set the aperture/shutter speed, while using the flash to produce well exposed photos.

The first thing is probably to realize that when you use the flash, you are taking two exposures. One is the background (aka ambient) where you'd set your camera as you would normally without flash, to get the desired exposure. The other is the foreground that the flash presumably illuminates. By the way, they're not mutually exclusive (i.e., the foreground subject also has some ambient light hitting it, and the flash will spillover to some of the background).

The second thing to know is that, with ETTL, the camera decides the output of the flash based on reflectance of the scene, by firing a preflash then using the resulting data to do the real flash. This is part of the flash metering process.

So, to answer the question, use your camera settings as you normally would without flash, to get your background exposure. This means setting the appropriate aperture, shutter speed, and iso. Sometimes, it is OK to keep the background underexposed, so you can experiment by keeping the indicator 1 or 2 stops under.

Once the background is taken care of, deal with the foreground exposure by controlling the flash output. Depending on your shooting mode (P, Av, Tv, M), the flash metering behaves differently. Perhaps in many cases, ETTL will correctly determine the flash output needed. In some cases, it can get confused by the scene and so what you can do is dial in the appropriate FEC to reduce or increase the flash output to get the desired exposure. This can be a trial-and-error process especially if you shoot in all types of lighting conditions.