Digital SLR single-point focusing: how to focus first and then compose?

The correct way is to compose the picture before focusing. I should concentrate on you before composing. Whether you change the focal length or move the position. Will cause a focus shift. Finally, the photo is blurred (this is related to the aperture and focal length. If the aperture is small or the lens is at the wide angle end. Slight focus inaccuracy does not affect the clarity. )

If you have ever used a lens like 85/ 1.4 or 70-200/2.8. You know what the point is and where it is. Where is clear, the place before and after the focus is blurred. Like taking portraits. Strictly speaking, we must focus on the human eye. When the position of the human eye has no focus. Try to focus on people's clothes. (Other focal points are also possible. Only when you want to see the focus clearly from the viewfinder.

Press the shutter.

The role of AE-L is not only to lock the focus. You can also lock exposure value in files A and S ... but there is no tripod. It's best not to lock the focus with AE-L, because that slight jitter is more likely to blur the image. In particular, the high-end direct-shot handle SLR. For example, Nikon D2X, Fuji S3 and so on.