Working with Automatic Focus
Posted by Tali Weissberger at 5:53 pm
Automatic Focus is now a standard feature on almost all cameras. You can choose to use this feature by pushing down the shutter-release button on your camera slightly, as the camera adjusts the lens to focus on (most often) the center of the screen -or what the camera assumes is your subject.
There are times though that this auto-focusing can cause problems, especially if your subject happens to be to the left of center, and turns out blurry, while an inconsequential object in the center of your picture is focused. In such cases, you can manually focus the camera to bring your chosen subject into focus.
The first step is to look for the auto-focusing ‘brackets’ in your camera:
Notice the Auto-Focus 'Brackets'
If you wanted to focus on the left portion of the bridge for example, instead of the center, simply place the auto-focusing ‘brackets’ around the main subject (the left bridge support) and partially press down the shutter-release button. Keep the focus locked by maintaining partial pressure on the shutter release. Next, re-frame your picture: maintaining this partial pressure, press the button down all the way in order to take your picture with its chosen focus subject.
Do you have any ideas on ideal conditions for using or not using the auto-focus on your digital camera? Or how to take the optimal photo with this feature? Let us know in the comments section below, or on the Contact page
One bit of information I always found useful when trying for the sharpest photos is, since no lens is at its optimum sharpness at ALL F stops, manufacturers pick the F stop 2 stops down from the maximum lens opening, and do whatever lens manufacturers do to make that the “sharpest” point for that lens. I have never been able to disprove this, so I preach this bit of information when discussing lens sharpness.
On a lens with a maximum opening of F 2.8, the optimum sharpness of this lens would be at F4.5.(on most lenses of this speed). To make maximum use of this “optimum sharpness”, you would set the aperature at F4.5, and use either the shutter speed (for stopping action), or diaphram, (for depth of field) to get the proper exposure.
As I said, I have never found this to be otherwise. It applies to any lens (many) I have ever used.
It also applies to enlarger lenses (the optimum sharpness bit). Use the timer for proper exposure. Smaller F stops can increase “depth of focus”. Another matter all together.
Anyone in an opposing view? JG