Sigma 50/50e manual Other Camera Controls & Features, Auto Exposure Lock Button

3)Auto DX film speed setting 0 = on, 1 = off

4)Use of * button

0 = AF start with shutter button, exposure lock with "*" button 1 = AF start with "*" button, exposure lock with shutter button 2 = same as 0, plus DOF check with "*" button

5) Mirror lock with self timer

0 = normal ten second self timer,

1 = mirror locks up and the self timer becomes two seconds

6)Second curtain flash sync 0 = off, 1) = on

7)AF assist beam 0 = off, 1) = on

8)Spot & FEL to focus point

0 = Partial meter & Flash Exposure Lock at center point only 1 = Partial meter and FEL follow the active AF sensor

9) Force 1/125 sync in AV mode

0 = In Av mode with flash provides full ambient exposure 1 = In Av mode the shutter is locked at 1/125 second

10)AF indicator lights 0 = off, 1) = on

11)Eye control DOF preview 0 = off, 1) = on (Elan IIe only)

3 Other Camera Controls & Features

3.1 Auto Exposure Lock Button

Just behind the top mounted LCD are two thumb buttons. The one on the left is the AE Lock button. It's marked with a "*-cf" symbol. The "cf" part of the symbol is to denote that it is used to set the values of the custom functions, explained above. When the camera is not set to the CF mode on the Command Dial, the AE Lock button can do several things. Its primary purpose is to set the exposure for one scene and then recompose the picture. This works particularly well with partial metering where you want to meter a subject but compose the scene with the subject off center.

Normally pressing the shutter button half way activates autofocus, and pressing the AE Lock button locks the exposure value that is determined by the camera's metering system. This is called Auto Exposure Lock (AEL). However, if custom function #4 is set to "1" the functions are reversed. The primary reason you might want this is to move your auto focus away from the shutter button. That way you would only reactivate AF when you wanted to, not every time you press the shutter. If you couple this with Canon's USM lenses that allow Full Time Manual focusing (FTM), you can autofocus by the push of the "*" button, and manually focus by turning the focus ring on the lens, all without switching the AF/MF switch on the lens. This may not sound like a big deal, but for many photographers this is the primary reason to buy Canon equipment. The low end line of Canon lenses use a micro motor USM that does not allow FTM, so pay attention to what you're putting your money down for. USM stands for UltraSonic Motor. They are nearly silent and the mid and upscale ones are fast!

Nikon has recently started selling a few Silent Wave lenses that are essentially the same thing as USM. Only some of the high-end lenses have this "S" designation and

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