Question:
How do I better focus my E-System camera in low light situations?

Answer:
Here's the trick -- first you have to understand how autofocus works. Autofocus uses a phase contrast detection system wherein the AF Frame has to find a difference in contrast so that when it searches for the focus point it uses an edge and seeks to sharpen that edge. If the AF Frame is on a solid area with little or no contrast, the camera will hunt for the focus and will not allow the shot to be taken. If you place the AF Frame on an area that exhibits contrast, the camera will focus. If the camera AF Frame selection is set to AUTO, it will pick an AF Frame and will usually default to a frame where it can find the contrast it needs. However, that may not be the area that you want it to focus on. So, the first step is to change the AF Frame from AUTO to the center frame. That's the button on the far upper right of the camera back.

Now you need to find an area of contrast in the frame that is in the area you want focus in and place the center AF Frame on that high-contrast area. But if you do that it doesn't give you the composition you want. No problem -- all of our digital cameras have Autofocus Lock (AFL). When you press the shutter button halfway down, the camera locks the autofocus, and then when you press the shutter button all the way down it shoots the picture. If you position the AF Frame over the high-contrast area, press the shutter button down halfway, recompose the picture holding the shutter button down halfway, and then do the full press you will get a properly focused picture with the composition you want. When shooting in low light -- and even in daylight -- look through the viewfinder and constantly give the shutter button a half-tap. This is called "feathering" the autofocus. This involves some anticipation of what is going to happen.

Here’s an example: Imagine you’re shooting a marathon with a very long lens, and you have a pretty good idea of the composition you want to end up with -- showing a runner against a beautiful background. Track the runner before he/she gets to the composition you want, but continuously press the shutter button halfway to get focus and then let it up. Another half-press and release as you pan. Again. Get close to the final composition. Again. Another half-press and then the full press when the runner got into position and you’ll get your shot.

If you get used to using Autofocus Lock, you can time your shots down to a split second and get your focus. In low light, you can do the same thing by giving the camera some contrast to focus on and quickly recompose with the shutter button held halfway and then doing the full press to get the picture.

If you are getting blur, it may be that you should use a higher ISO in low light. Instead of relying on AUTO ISO, try presetting an ISO.

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