An Example of the Flash Exposure Lock (FE Lock) Button

[Steve Eisenberg]

In my previous post regarding the mysterious "asterisk" button (An Example of the Auto Exposure Lock (AE Lock) Button) ("/forums/t/321.aspx), I described how/why to use the button without the flash.


In this case, the button is used with the flash on, but why? You may notice that when you see folks using digital cameras with the flash on, it actually flashes twice. The camera pre-flashes, and takes a reading based on the subject in the foreground. And the flash assumes the foreground to be in the middle. I realize that you could choose other focus points, but in my opinion, if shooting "on the fly" and not posed, you will not likely have a chance to fiddle with the settings. You will set up the camera for the overall situation, and shoot. In this case, it's reallyeasy to have your fingers on the buttons needed.


These two photos were shot with the Canon XTi, 50mm f1.4, with a flash (without the flash it's "Auto Exposure Lock", but we're not dealing with that in this post), on "P" mode, one shot auto-focus, center focus point, center weighted metering, ISO 100. f2.8 1/60.


In this first example, I focused on the face of the kitty (holding the shutter button halfway down), recomposed, and shot. As you can see, the subjects face is in focus, but overexposed. And the background is out of focus, but nicely exposed. The flash did it's pre-flash after I recomposed. So it metered off what it considered to be the foreground, the center of the image (the background).


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In the second second example, I placed the kitty in the center of the viewfinder and pressed the "FE Lock" button (the "asterisk"). This action fired a pre-flash and metered off of the foreground (the middle, the kitty). Then I focused on the face of the kitty (holding the shutter button halfway down), recomposed and shot. In this case, when the shutter button was pressed all the way down, there was only one flash, as the pre-flash had already occurred. As you can see, the foreground is better exposed, and the background has faded back.


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Now whether the second photo's exposureis pleasing is a matter of opinion. I made no changes to the brightness or contrast before processing. And just to reiterate, my examples are based off of using the center focus point; What I consider to be the most user friendly method when handholding the camera for "grab" shots.


Whatever you do, do not adjust your distance or focal length while using the "Lock" button. Especially when using the flash, it will mess up your camera's calculations


In taking flash photos with digital cameras, there's a good chance that the pre-flash could cause your subjects to be blinking during the actual exposure. If you pre-flash in advance, even if you aren't recomposing, this can be avoided as the subjects will see/react to only one flash at a time. It's all a reflex, the subjects probably have no idea that they are reacting to a pre-flash, and potentially having their eyes closed for the actual exposure. I tend to remind people to keep their eyes open (without getting into the nitty-gritty details of it). And I like to pre-flash animals, if there's time, because they don't seem to understand English. Perhaps it's the dialect I'm using.

[twistedphrame]

Thanks for these posts, they explained this much better than my manual. I have an XTi too and does the FE and AE lock hold the exposure for multiple photos, say I take one or two, adjust how much is in frame and shoot again, or would I have to use the * multiple times?


Many thanks,


~Jordan

[Steve Eisenberg]

Thanks for these posts, they explained this much better than my manual. I have an XTi too and does the FE and AE lock hold the exposure for multiple photos, say I take one or two, adjust how much is in frame and shoot again, or would I have to use the * multiple times?


Many thanks,


~Jordan
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You can take multiple shots for as long as the settings hold (AE Lock 4 Seconds/FE Lock 16 Seconds). You can hold down the AE Lock for as long as you want, but the FE Lock fires a pre-flash, so that wouldn't help. You can shoot a burst by just pressing the button once either way.


Whatever you do, do not adjust your distance or focal length while using the "Lock" button. Especially when using the flash, it will mess up the cameras calculations (I'll add that to the post).


I Hope that helped!

[Dann Thombs]

Thanks for the post. I shamefully admit thatI've let the * button remain a mystery. I mean I know what it does, but never to the point of using it in practice.

[Steve Eisenberg]

It's great to use with and without the flash (different funtions)


Using it for exposure lock (no flash) is something I do every day. For example: A birdfeeder brightly sunlit on one side, the other in shade, the background darker shade, and the foreground totally bright, sunlit grass. I set the camera to center-weighted metering, and press exposure lock button, while looking at each area throught the viewfinder. Then compose on the birdfeeder and shoot for each setting. Or on a contrasty street scene, meter (exposure lock) off of the nice grey pavement. I use center-weighted metering, rather than spot-metering, as spot-metering can take the exposure settings too far.

[Dann Thombs]

These are great tips for flash. For normal exposure, I usually find the best settings, then jump to manual mode. But for flash, most of that info isn't readily apparent, so this will save me some time.