The Power button on EOS cameras.

<p>Allot of people have complained about the Power(ON/OFF) switch on Canon EOS cameras. They look so flimsy, but so far I haven't broken one yet, or have the switch malfunction on me. <br />If you own a Canon EOS there are 3 functions on the power switch. ON/OFF/ON (APERTURE/SHUTTER) LOCK. The (APERTURE/SHUTTER LOCK) is the most confusing. Most people would say "Why do I need this ?".<br>

<br />However, I found it to be very handy for the type of work that I do. I shoot rapid-fire assembly type portraits of little leaugue sports teams on weekends. Often I shoot about 350+ kids on a given day. In those type of situations, it is very, very easy to fat-finger the exposure settings on the camera. You might start out with a setting of let's say f11 and 1/125th, but by the time you shoot a couple of teams, the exposure has misteriously changed to f5.6 at 1/60th !<br>

<br />By the time you realize it, it is too late. That's when you hear it from the people that do our printing, because they have to reset the printers each time the exposure changes drastically like that. By using he exposure lock on the Power switch you avoid all these problems, FYI...</p>

<p>Curious as to which "EOS" cameras you are referring to? I have a Poweshot XS10 and it only has an on/off button. My XSi DSLR has an on/off lever; it was the same on my previous 3 Digital Rebels. My previous Powershot S5 had a button for on/off or playback. I don't have any experiences with other Canon cameras.</p>

<p>My XTi does not have a switch like that either, but since I've never had my exposure mysteriously change, except for when someone borrowed my camera and left it on the auto mode, I don't think I'm missing anything.</p>

<p><em>If you own a Canon EOS there are 3 functions on the power switch. ON/OFF/ON (APERTURE/SHUTTER) LOCK.</em></p>

<p>My 5D also doesn't have this setup. It has a 3-position switch, but the settings are off/on(control wheel inactive)/on(control wheel active). Which camera are you talking about?</p>

<p>"My 5D also doesn't have this setup. It has a 3-position switch, but the settings are off/on(control wheel inactive)/on(control wheel active). Which camera are you talking about"<br>

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Ok, maybe (control wheel inactive)/on(control wheel active) is a better way of explaining it. The control wheel controls the exposure. My mistake, it does not control the shutter speed. In any case, you would not beleive how easy it is to change the exposure inadvertantly while you are firing away. When you set the Power switch to the second position it locks the exposure wheel. I have always wondered about this function and I'm sure others have as well, but now I know why ! Both my 30D my 5D and the 40D I use at work, have this function. I'm not sure about the XTi...</p>

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<p>you would not beleive how easy it is to change the exposure inadvertantly while you are firing away.</p>

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<p>Never done it once. And I shoot in fairly intense situations where I can't spend time thinking about switches on the camera.</p>

<p>I think I looked up the function of the 3-position power switch (it's clearly explained in the manual) the second day I owned the camera. Its purpose seemed pretty clear.</p>

<p>The 3 setting switch (off, on / control wheel inactive, on control wheel active) has been a feature of the high end Canon bodies for many years. I am not sure about the EOS1 as I have never owned one but the 1N, 1V, 3 and subsequent bodies all have this switch. In the 1NRS it was modified as there was off, on and RS (high speed) modes. I have never found that i need the middle setting with the control wheel inactive.</p>

<p>EOS cameras with rear control dials have a switch for disabling the dial, so it doesn't get bumped accidentally. Some cameras have two separate switches - one controlling the power for the camera, and one controlling the dial. These two similar-looking switches seemed to confuse new users. More recent EOS bodies have a single power switch with three positions, as described above.<br>

Consumer EOS digital bodies have a single on-off power switch on the top.<br>

I've occasionally found the ability to disable the rear dial useful, though just as often I've found it annoying when the dial doesn't respond and I find I've left the power switch in the wrong position.</p>

<p>I just leave mine on all the time, so it doesn't matter...</p>

<p>I can testify that it is possible with the three-set switch on full, that you can <em>accidently</em> shift the exposure compensation with the camera rubbing against things. The first time this happens, you wonder what's got broken......</p><div></div>

<p>I have to reacquaint myself with the three position switch and rear wheel after not using the Eos for awhile.</p>

<p>I always leave mine in the second "on" position to enable the quick control dial on the back of the camera. I use that to set aperture values quickly. I can't say I've ever moved it inadvertently that I recall.</p>

<p>heh....never had exposure problems with rear wheel engaged.....actually my only problem with the power switch is sometimes, somehow it shifts to the middle position on me....must be the way i hold the cam or grab it sometimes.....and then I wonder why ALL the controls aint working for me. Sometimes wish it had a locking control to it. Love that rear wheel control.</p>

<p>Yes Canon40D, does have 3 positions.</p>

<p>I wonder if the people who disable the real wheel use their left eye on the viewfinder. Like many above I use my right eye and always turn the wheel on - i have never had a problem. Indeed on the 1NRS there is no option on the three position switch to disable the rear wheel as they use the extra position for RS mode. JDM and Harry do you put your left eye to the viewfinder?</p>