If I zoom in to focus, halfway press the shutter to set focus and exposure, then zoom back, will it stay in focus? Does zooming back out change the focus?
Yes it does and it also greatly affects your depth of field.
Try it out. The price of digital film is cheap.
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R1 and H5 photos here: http://www.flickr.com/photos/grossinger
If you are using "monitor AF" mode or "single" mode, the focus will remain as long as you holg the shutter button at half-click. If you're using "Continuous" mode, it will continue to refocus.
Now, the question is, will that focus apply over the entire zoom range? Not quite. The zoom range is huge on this camera.
But, it will work over a suprisingly large portion of the range. I often focus at full zoom and then zoom back out a bit to reframe the picture to include the entire subject with excellent results.
