Help with autofocus on the 40D

<p>Good evening,<br>

I've been working on trying to figure out all of the different autofocus options on the 40D (using multiple manuals, books, etc) but am still running into one problem. I would like to be able to keep ALL of the people in focus of a wide angle shot. As of now, the photos I've taken have one particular area in focus and not the entire photo. How do I shoot a family photo (with 15+ people), keeping everyone in focus?<br>

I hope that makes sense!<br>

Thanks!</p>

<p>Read the manual. It gives multiple options for keeping one or multiple objects in focus. You have to set focus points following steps described in the manual.<br>

For many practical uses, it is better to keep only one central focus point on, instead of multiple. Multiple focuses, after all is a compromise. So you compose / focus the most important object (using the central focus only) / keep the finger on the shutter / recompose / shoot. </p>

<p>Use a smaller lens aperture (larger number) to begin with. Something like f/8 or f/11 will usually work with a wide lens. You will need more light or higher ISO settings to keep your shutter speed up though, so you may want to use a tripod to keep the camera steady. The smaller aperture will increase the depth of field (also called depth of focus), keeping everything from near and far more closely in focus.</p>

<p>The next trick is to focus on something in between the front and back distances. Preferably 1/3 the way into the group, as there is more DOF coverage in back of the focus distance than in front of it.</p>

<p>For groups I usually use manual focus, or multiple focusing points. Or I might use one focusing point then tweak manually.</p>

<p>A lot of good info can be found here: <a href="http://toothwalker.org/optics/dof.html">http://toothwalker.org/optics/dof.html</a> (you don't have to read it to the bottom). Photozone.de has an interactive page about dof: <a href="http://www.photozone.de/depth-of-field">http://www.photozone.de/depth-of-field</a> There are lots of similar places on the web that offer an explanation about dof, just do a google search.</p>

<p>Kate, can you supply us with an example or two including the exposure information, shutter speed and f-stop at least.</p>

<p>A lot of these focusing issues have less to do with how you're metering and more to do with how close you're standing and what f-stop you're shooting at. If you're at a lower f-stop (wider aperture) you're going to get much less in focus, and that will account for many of your subjects being out of focus, no matter how you meter all of them.</p>

<p>Kate ... are you using the 'half-trigger' technique? Here you half press the trigger with you single focus point on the subject matter you want to be the focus point , when the camera tells you it* has found focus you continue to hold HT while re-composing for the shot you want, then complete full pressure on the trigger to take the shot.<br>

This is a technique that many use and would work well with Jim Strutz's advice to focus on a point one third of the distance through the group of people you are photographing. If you also go to <a href="http://www.dofmaster.com">www.dofmaster.com</a> you will find an interactive page where you enter the details of your camera and pick a focus distance and it tells you how much depth of field you have. This will tell you as to if what you are trying to do is likely to be practicable ... becuase a group of people can be arranged in various ways from a 'flat' arrangement to an 'in depth' version and you need to know what is possible at different apertures/lens. Your use of a wide-angle lens suggests to me you may be trying to capture the 'in depth' style of grouping which can be hard.<br>

*almost instantanious with a DSLR<br>

For the extreme 'in depth' style you might want to try taking two or more shots focusing at different points in the group and combining in editing. I did this only on Xmas Day when I couldn't get my 'new' camera to give me a 10 second delay shot so I took a shot of my wife in shot and then she took a shot of me ... combined in editing to be sent to distant family as christmas greetings.</p>

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<p>I would like to be able to keep ALL of the people in focus of a wide angle shot. As of now, the photos I've taken have one particular area in focus and not the entire photo.</p>

</blockquote>

<p>It's hard to say without seeing a photo, but this sounds like something that has nothing to do with the camera's autofocus settings, so reading the manual won't help much. The autofocus settings control what part of the image the camera uses to set focus. That will determine who in a group the camera uses to set the focus. How MUCH is in focus depends on how the people are arranged (are they in a plane parallel to the camera sensor, or at varying distances) and the depth of field. Depth of field depends on aperture: the smaller the aperture (the larger the f-stop number), the greater the depth of field. . The readings Jos suggested are good ones. Another is http://www.cambridgeincolour.com/tutorials/depth-of-field.htm.</p>

<p> </p>

<p>One problem with single focusing points and I shoot allot of groups, is that suppose you have a group of 3 people. Suppose these three individuals are lined up in parallel. One is on the left, the other is on the right and one is in the middle. If you put the focusing point on the person on the right, there is a very good chance that the persons on the left and in the middle will be slightly out of focus.<br /><br />Same goes if you place a single focusing point on the person on the left. Your best bet would be to place the focusing point on the middle person. However when shooting groups its not that easy, because groups are not allways lined up in parallel. You can force them to be in parallel, but that might ruin the composition(or the clients particular need) .<br /><br />Suppose you line up one person in the front, another person slightly behind that person and the third person slightly off to the right, things then get a little bit more complicated. That's why I always switch to manual mode in those situations.<br />For large groups where the subjects are lined up in rows, you can place the focusing point on the middle row and use a small aperture such as f8/f11, but suppose there are 5 or more rows then what ? Suppose the first row is sitting or kneeling down and the rest of the rows are standing up ? For large groups such as these make sure you are standing far back enough so that the DOF can take effect, and use a wide angle lens not more than 50mm.<br /><br />Some cameras like the Canon 7D allow you to select multiple focusing points, but good luck with that, because people tend to move around allot during the posing stage, so selecting predefined focusing points make this a useless endeavor.<br /><br />You can also let the camera choose the focusing point which is something I do when I'm in a hurry or when I'm shooting in very dim light . Just keep pressing the focusing point button until multiple little squares(focusing points) light up in the viewfinder and fire away. This is not the best option, but it works sometimes.</p>

<p>Thanks all for your responses and advice!</p>