An Example of the Auto Exposure Lock (AE Lock) Button

For those who wonder what the asterisk (*) is there for, it's called the Auto Exposure Lock (AE Lock) button:


These two photos were shot with the Canon XTi, 50mm f1.4, without a flash (with the flash it's "Flash 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 1600.


For this first shot I focussed on the face, recomposed and shot atf1.4 1/25 As you can see, the metering took the background into account,as well as the forground. And in attempting to better expose the background, the camera forced an overexposure, as well as a shutter speed too long for being handheld.


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.24.20/IMG_5F00_4758.JPG[/img]


Next time I centered on the body of the subject, pressed the "Auto Exposure Lock" button, then focussed on the face, recomposed and shot at f1.8 1/80. The subject is properly exposed, the distracting background fades away, and the picture is sharper due to the shorter shutter speed (the smaller aperture helped as well).


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.24.20/IMG_5F00_4760.JPG[/img]


The first shot may have worked ot with "Partial Metering", but sometimes while photographing animals, youarestuck without the time to fiddle withtoo many settings. And some of the background may have been brought in as well. Bracketing may have also worked too, if already set up to do that. The "AE Lock" button is one of the features I use every time I pick up the camera.

Thanks for the examples, many other my take it for granted that this procedure is a given to them but for me it gives me something to use forcomparisonand practice.


Please, keep up the good examples...

Another opportunity to use AE lock is for back lit situations. I shoot weddings and during the processional the back of the church is often back lit because the doors are open or it is mostly glass. To get the proper exposure of the wedding party coming down the isle I expose downward to the carpet and lock exposure. By holding the button down I am able to shoot the entire wedding party and they don't look like silhouettes.
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="ProgId" content="Word.Document" />
<meta name="Generator" content="Microsoft Word 11" />
<meta name="Originator" content="Microsoft Word 11" />
<!--[if gte mso 9]><xml>
<w:WordDocument>
<w:View>Normal</w:View>
<w:Zoom>0</w:Zoom>
<w:PunctuationKerning />
<w:ValidateAgainstSchemas />
<w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid>
<w:IgnoreMixedContent>false</w:IgnoreMixedContent>
<w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText>
<w:Compatibility>
<w:BreakWrappedTables />
<w:SnapToGridInCell />
<w:WrapTextWithPunct />
<w:UseAsianBreakRules />
<w:DontGrowAutofit />
</w:Compatibility>
<w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel>
</w:WordDocument>
</xml><![endif]--><!--[if gte mso 9]><xml>
<w:LatentStyles DefLockedState="false" LatentStyleCount="156"]
</w:LatentStyles>
</xml><![endif]-->
<style>
&lt;!--
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-parent:"";
margin:0in;
margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;
mso-header-margin:.5in;
mso-footer-margin:.5in;
mso-paper-source:0;}
div.Section1
{page:Section1;}
--&gt;
</style>
<!--[if gte mso 10]>
<style>
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:"Table Normal";
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-parent:"";
mso-padding-alt:0in 5.4pt 0in 5.4pt;
mso-para-margin:0in;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.0pt;
font-family:"Times New Roman";
mso-ansi-language:#0400;
mso-fareast-language:#0400;
mso-bidi-language:#0400;}
</style>
<![endif]--><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit"]
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->

I also use exposure lock for quick panoramas although PS does a good job of automatically correcting exposure between frames. It probably cuts down on the processing time.