Flash Exposure Compensation

There are two different kinds of exposure compensation. Overall exposure compensation is set on the camera body and affects both the ambient and the flash exposure for Nikon, but only the ambient exposure for Canon. Flash exposure compensation affects the flash output only; the ambient exposure is unaffected. This can always be set on the flashgun itself, but some cameras also have a button on the camera body where the flash compensation can conveniently be set without taking your eye from the viewfinder.

Overall exposure compensation is used with the automatic metering modes. However, with most Nikon cameras, dialing exposure compensation in the manual exposure mode will bias the camera's built-in light meter even for manual exposure. With Canon, you can't dial exposure compensation in the manual exposure mode (see sidebar above).

Flash exposure compensation is used to compensate for the flash output when the flash is used in Auto or TTL mode. Obviously, it can't be set when the strobe is used in the manual output mode.

First, let's review exposure compensation in general. There are two concepts to keep in mind:

Cumulative Exposure Compensation with Nikon Cameras

The Nikon bodies I have worked with allow you to set overall exposure compensation even when you have your camera set to the manual exposure mode. This allows you to bias the metering.

With Nikon, the overall exposure compensation and flash exposure compensation is cumulative—at least to an extent. For example, if you were to dial in +1.0 EV overall exposure compensation setting on the camera and -1.0 EV flash compensation setting, they would cancel each other—but only for a scenario where the ambient light is low and the flash was your main source of light. Where the ambient light levels dominate, and flash is used as fill only, different algorithms come into play. Factors such as the flash-sync speed and available apertures affect the scenario as well. Hence, the flash and exposure compensation might affect the ambient light exposure differently.

With Canon, flash exposure compensation and overall exposure compensation aren't linked in this way. With a Canon D-SLR in the manual exposure mode, you can only set the flash exposure compensation, not the overall exposure compensation.

With Canon, you can't dial exposure compensation in the manual exposure mode . . .

1. When the scene/subject is light in tone, you'll increase exposure.

2. When the scene/subject is dark in tone, you'll decrease exposure.

As discussed in chapter 5, this is due to the fact that your camera's meter will suggest an exposure setting designed to render everything as a middle gray tone. Hence, if you are using one of the auto modes (or Auto/TTL flash) with no exposure compensation, someone in a white dress against a white wall will be underexposed; you need to bump up the exposure compensation for lighter-toned scenes. The same reasoning goes for darker-toned scenes. A man in a

You have to adjust your flash exposure compensation in response to the tonality of the scene . . .

dark suit against a dark brick wall will be overexposed if the camera is allowed to make its own decision; you need to reduce the exposure compensation setting for darker-toned scenes.

To make it even more clear, let's think about this scenario. We have a setting where the light is consistent and even—so there will be an exact combination of aperture/shutter speed/ISO settings that will provide the correct exposure for the skin tones. Yet, if our subject dresses in all black or all white clothing, our automatic meter reading will change—even though the light hasn't changed. We would still need the same exposure, regardless of the variation in our camera's light meter reading. If you insisted on using automatic exposure, you would have to use exposure compensation to compensate. Further, you would have to vary your exposure compensation depending on your composition; the size of the light/dark patches of clothing and background areas would also affect your meter reading.

The same reasoning goes with using Auto/TTL flash: you have to adjust your flash exposure compensation (FEC) in response to the tonality of the scene in front of your lens.

With TTL/Auto fill flash, you will most often dial down your flash exposure compensation to give only a tiny bit of fill light. Your flash exposure compensation will be around -1 to -3 EV. (Again, this depends on the tonality of your subject.) When your flash is your main source of light, you will usually hover your flash exposure compensation around 0 EV to +0.7 EV, depending on the camera, the camera system, and—of course—the tonality of your subject and scene. So your flash exposure compensation could still range anywhere from around -2 EV to +3EV.

Once again I want to stress a particular point: there are no specific or fixed settings. There are just too many variables for anyone to give specific do-it-all settings. The factors that would affect how much flash exposure compensation needs to be dialed in include:

1. The reflectivity of your subject

2. How much of your frame is filled by the subject

3. How far the subject is from the background

4. Whether the subject is off-center or centered in the frame

5. The individual camera's exposure algorithms

6. The available light (this ties in with how the camera's metering algorithms work)

7. Any backlighting (strong backlighting always requires a lot more flash exposure compensation)

Therefore you have to juggle all this when figuring out how much flash exposure compensation to dial in. This is a seemingly tough task that gets easier with experience. Here's a hint, though: when your flash acts only as a fill light, the flash exposure compensation can vary a lot without affecting the quality of the final image much. Fill flash exposure compensation of—2 EV will look slightly different than —3 EV, but the actual photo won't be incorrectly exposed with either setting. If your flash is the main source of light, on the other hand, a full stop incorrect exposure would be a lot—and it might very well mean the image is a flop in terms of exposure. Careful and subtle use of flash should always be the aim, of course.

The actual amount of flash exposure compensation can be fine-tuned by looking at the camera's LCD. Adjust it to taste; don't get stuck on the specifics. Here's a rough guide to get you started with making flash-exposure compensation settings for fill flash:

fill flash in the same direction as the sun (or available light): —3 to —1 EV fill flash 90 degrees to the sun (or direction of available light): —2 to 0 EV fill flash against the sun (or direction of available light): —1 to +1 EV

The exact ambient exposure here will depend on what the background looks like and how it is lit. For example, you could allow the background to blow out a bit (overexpose it) and then use just a touch of fill flash on the subject, who is shaded against the ambient light. In this case, a setting of—3 EV would work even when shooting against the direction of the sun (or direction of the main source of available light). As I said, don't get locked into specific recipes. Adjust your settings to taste by thinking about what you're trying to achieve.

The conclusion here is that, ultimately, it is best to know how your specific camera and flash reacts in various scenarios and various lighting conditions. There is only so much that can be learned outside of actual experience and continual practice. You have to know your equipment.

The exact ambient exposure here will depend on what the background looks like . . .

Digital Cameras For Beginners

Digital Cameras For Beginners

Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.

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