Greetings, I have had more tha one occasion on my EOS 1n where the exposure compensation button was accidentaly pressed and in turning the main dial I have set my exposures incorrectly. I prefer to make my compensations via f stop or shutter speed or bracket. Is there a way to lock out this feature? The only options I know of is to change the steping rate in the custom functions but no way to lock out the feature. Any help is greatly apprecieated. Thanks. J

-- John DeSantis (johnsbox@sunlink.net), September 30, 1999

Answers

John: On the In, exposure compensation is "dialed in" using the quick control wheel on the camera back (operated with your thumb) once the rotary thumb switch adjacent to the quick control wheel is set to the "i" position ("i" = "in" meaning "turned on", as opposed to the "o" or "out" setting). As long as the switch is in the "o" position, exposure comp. is not possible or is locked in to a given amount that was previously set. In the latter case, one can set, say, -2/3 comp. and then set the switch to "o", and that amount of comp. will remain in effect until you unlock the switch and change it. I'm too lazy to check my manual right now, but unless there's a custom function that allows one to switch the functions of the two wheels with respect to dialing in exposure comp., what I'm saying holds true. As set from the factory, the main dial on the top left of the camera does not automatically control exposure comp. In Manual shooting mode, you must manually dial in changes to the aperture or shutter using the two wheels to effect exposure comp. (depending on custom fxn settings, one wheel controls aperture; the other, shutter speed). Remember, the rotary thumb switch to the left of the quick control thumb wheel enables or DISABLES exposure comp. for all auto. shooting modes (this includes P, Av, Tv, and DEP modes)!!! Be sure to read and RE-READ your owners manual until you KNOW the camera! In fact, there is no exposure compensation "button"; there is only the thumb switch and the quick dial. In Av mode (aperture value or PRIORITY), the camera will hold aperture constant at the value you tell it, while varying shutter speed to achieve the desired comp. In Tv mode, the converse is done. In P mode, the camera's on-board brain decides which value to change, and its decision is often based on its knowing the focal length of the lens being used. For example, if your using a 400mm lens, the P mode brain will likely try to accomodate your request for a positive change in exposure comp. by (if possible) opening the lens up while simultaneously trying to preserve the fastest possible shutter speed, because it knows that longer lenses need faster shutter speeds for handholdability. It does not know if you're using a tripod!

-- kurt heintzelman (heintzelman.1@osu.edu), September 30, 1999.

Correction (sorry): the main dial is, of course, on the top RIGHT of the camera body (and is controlled by the right index finger).

-- kurt heintzelman (heintzelman.1@osu.edu), September 30, 1999.