March/April 2009: Helpline
Holding Steady: Presetting Exposure & Focus | Stable-Enabled
Presetting Exposure & Focus
In my last column, I tackled a question about shutter lag. The reader was frustrated with his camera and how the shutter-release button caused problems.
“When I take pictures, it seems I have to press pretty far on the shutter button to get the camera to take a picture. Because of this, I have noticed that my having to press the shutter down so far seems to add movement to the picture and this shows up as blur.”
His frustration led to asking about possibly modifying the camera. Once I got him to put down the drill, I explained how the modification in all likelihood wouldn’t work. But I promised that this month I would offer some suggestions to help reduce blur.
First, make sure you press on the shutter release properly. When I teach beginning photography classes, I have the students go through an exercise where they gently press down on the shutter release. I explain to them how to slowly increase the pressure until the shutter releases. If they do it right, they should be surprised when it goes off.
Now this doesn’t mean that you should be surprised when taking pictures; this is just practice. The main idea is that you want to avoid jerking the camera when you press down on the shutter release. Eventually, this practice leads to a gentle finger.
Blur also can occur due to the delay caused by “shutter lag,” even if you have a light touch. Often, a photographer releases his or her firm hold on the camera before the camera takes the picture.
While shutter lag is inherent in any camera, you can reduce some of the lag yourself. When you press the shutter, the camera has to decide on focus and exposure. If there was a way to take over that decision-making by your camera, you could speed up the process.
The simplest method to do this is to press the shutter down halfway, well before you take the picture. With many cameras, this half-cocked shutter forces the camera to lock focus and exposure on the scene. Then, when you press the shutter release all the way, the camera doesn’t have to think about exposure or focus; it just captures the image.
Keeping the shutter-release button held at the halfway point without taking a picture can be a little difficult. The shutter release exercise I mentioned earlier actually can help with finer control of the shutter-release button.
Note: Some cameras allow you to change how exposure and focus are locked when the shutter release is depressed, so check your manual for your camera’s custom settings.
Your camera may have special buttons for focus lock or exposure lock. Look for terms like AE lock (auto-exposure lock) or AF lock (autofocus lock) in your camera’s documentation. While these generally are used for difficult focus or exposure situations, they also can be used to speed up the picture-taking process.
By pressing the AE lock or AF lock ahead of time, you shorten the time between pressing the shutter-release button and capturing the image.