Monday, February 10, 2014

Brave New World of Back Button Focus

[Note: Due to a scouting trip to South Carolina, blogs will be sporadic this week. The blog will be back on a normal schedule starting Monday, February 17.]

In the old days before autofocus was invented, the shutter button had only two functions: press down partway to take a meter reading, and then press down fully to take the picture. Focus was not tied to the shutter release. To focus in those days, you manually turned the focus ring on the lens.

But since the advent of autofocus, we now have 3 separate functions occurring on the shutter button. That was a poor decision on the part of camera manufacturers. By tying the focus function to the same button as tripping the shutter, it means that each and every time you press the shutter button, your camera attempts to re-focus. The net effect is that a series of images of the same subject can vary in focus even if neither you nor the subject has moved. Each time the lens has to hunt for focus, there is a good chance that it will not lock onto the precise area you want sharp.

But not to worry, there is an easy fix. You can remove the focus function from the shutter button and put it someplace else. Most camera bodies allow you to do that via the Custom Function menu. There is a setting that will change the focus function to a button on the back of the camera body AND will remove focus from the shutter button. For some cameras this requires two separate changes  -  one to activate a rear button on the camera to focus, and another to remove the focus function from the shutter button.

Each camera body has a slightly different way of making these changes. Most Owner's Manuals are notoriously bad at providing this information. The best way to get the information clearly is either on YouTube or other sites that will come up during a google search. This is the YouTube link  Once on the site, type in your camera body in the search box near the top of the window. Here are a few links to get you started:

for Canon 5D Mark III  -
for Canon 60D  -

for Nikon  -

If you own a Canon 7D, online instructions are inaccurate, so here are the steps to follow [NOTE that these instructions are for the Canon 7D ONLY]:

1.    Press Menu button
2.    Scroll down to C.Fn IV; Operation/Other
3.   Press set button
4.  Press set button again
5.  Default is shutter release button top left.  Press set button 3rd time
6.    Turn wheel on back clockwise one click to: Metering start (instead of Metering and AF start) and press the set button.  This disables the focus from the exposure release.
7.    Pressing the set button above returns you to the Custom controls screen.  Use the wheel to scroll down to the AF-ON button and depress the set button again.  This brings you to the AF-ON button screen.
8.   Use the wheel to select the AF field and press the set button. (It may already be selected as it is the default). 
9.  Depress the menu button 3 times to exit the menu.

If you have a choice, set the focus function to the "AF-ON" button on the back of your camera rather than other buttons that may also give you that option. 

This is still the same autofocus as always, you just press a different button than you did before. While you may balk at this at first, it is the best thing you can do for your photography of any subject, regardless of whether it is a stationary subject or a bird in flight.  

So now, when you press and release the back button to focus, focus will not change each time you press the shutter release.  If you are taking multiple shots of the same subject, and neither you nor the subject has moved, your focus has not changed. When you or your subject has changed position, or you move on to another shot, press and release the rear button to focus for the new shot.  

Now you can embrace the bold new world of focusing control!

Shutter Speed 1/100 sec.  Aperture f/2.8.  ISO 100.  Lens: Canon 100mm macro f/2.8.  Camera: Canon 40D.  Handheld.

TODAY’S QUOTE: “It takes a lot of courage to release the familiar and seemingly secure, to embrace the new.”  --Alan Cohen

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