50D AF points in use for AE?

[alex_dannenbaum]

<p>I am still learning the fundamentals of my Canon 50D. As you will see I am getting confused by the manual and references to using to the AF points for exposure. <br>

When I am trying to set my exposure to areas other than the center of the screen, I understand that the best technique is to have the exposure mode in (preferrably) partial or spot mode, meter the subject at the center of the scene then recompose the scene while holding down the shutter in the halfway position then take the shot. - at least I hope that is right. <br>

Now, I am trying to figure how to use the AE lock as described on page 103 of the manual. It has got me confused. The table at the bottom of the page indicates that in Manual Focus, when locking the exposure, the AE is applied at the AF point for Evaluative metering. Which AF point? ... the center or other selected points? I am also confused because Evaluative metering is so spread out, and not a single point like "spot metering". (ie. shouldn't spot metering be the technique employed for selecting an AF point?)<br>

Additional related questions:</p>

<ul>

<li>I had always assumed that the AF points were just that, locations of Automatic Focus, when the lens is set to automatic focus vs. manual. I did not think they had anything to do with Automatic Exposure (AE) am I wrong? </li>

<li>Is the AE lock the only time that the AF point is employed for exposure, or is it done whenever an AF point is identified? </li>

<li>Aren't all exposures in the 50D "automatic", but can be ajdusted using Exposure Compensation. Is there such a thing as a manual exposure?</li>

<li>When both compensating the exposure and locking the exposure, which is done first? (Do you compensate then lock? or lock then compensate?)</li>

</ul>

<p>Please help and aleviate my confusion. <br>

Thanx</p>

<p> </p>

[nathangardner]

<p>Spot metering only works on in the center of the frame, not on any other AF points. (I wish this was a possibility) Push the AE lock button when the camera is exposed on what you want. Focus first and keep the shutter pressed halfway while locking exposure. I think if you lift your finger from the shutter after pressing the AE lock button, it will reset exposure; so focus first, lock exposure, and maintain focus until the photo is taken. I like using this in AV mode the best b/c it will lock your shutter speed and there is no adjustment to be made. In manual mode, you really wouldn't need to use the AE lock button, you could just adjust exposure while pointing at your subject then recompose and the camera settings won't change.</p>

[alex_dannenbaum]

<p>Thank you for your comment. This is pretty simple, but the table phrasing really threw me off. Your comments made sense. I spent a couple of hours today, applying your approach to test images. I think I have the hang of it now. </p>