Originally posted by Deni Can you do this with any camera in general:
If the object you want to focus on is not in the center, can you just focus on it by half pressing the shutter button, then while you hold it half pressed (lock the focus), compose the picture?
Absolutely true, you can use the shutter half press to and AF-S to accomplish the same thing.
However, when you take a sequence of shots (this particular image it not a good example of a sequence) - once you release the shutter. You have to move go back to your point of focus - and refocus again. Also if you decide that you really do not want to meter off of a certain point and you have locked the exposure - by habit - I just release the shutter and half press it again to set it. In such an instance I the half press shutter would cause the AF to search again - I do not want that.
If you are using AF-C then using the AF button and not the shutter button allows you the photographer to have control. That is what I want - the control - I do not want to give up that part of the creative process to a machine that does not understand what I want to do.
Now do not get me wrong - any method of focusing is OK with me. Back in the film days - I would use the split screen viewfinder on my non Pentax camera to determine the object I wanted in focus - then use the DoF markings on the lens to determine where in the DoF's range of acceptable focus the subject would fall. Then I would set the exposure and ----- wait for it ----- compose the shot. Many times the subject was blurry in the viewfinder - but I did have confidence in the DoF scales and all of my experience. By decoupling the AF from the shutter button gives me the control I want - now if the Lens manufactures would just give me back my DoF scales - that would truly be sweet.
PDL