I agree that the camera appears to have focused on the nosecone, or even the front of the stand. It isn't bad overall, but it would have been better to focus closer to the middle of the pen.
The Canon Powershot G15 does have manual focus. The process, however, is rather cumbersome. It's very simple, however, to focus on the desired spot by holding the shutter release button partway down, then recompose, and shoot. The G15 will draw a box around the point of focus when press the shutter release button partway down, so you can easily tell where the camera is focusing.
The G15 does not support tethered shooting. The G10 did, but Canon removed that feature from subsequent G-series cameras.
That's basically how manual focus works on the G15, except that you don't have to physically move anything. You zoom in on the camera's display, and then fine-tune the focus.
The camera does not have "fixed focus positions". Don't confuse lens focal length with focus. They are two different things. The G15 does have an option to choose fixed focal lengths (a feature looking for a purpose), but that is completely independent from focusing.
See page 130 in the Canon Powershot G10 manual for instructions on the G10 manual focus.
Do whatever works for you, but the only time I ever move the camera to achieve focus is when I'm taking macro shots (typically with an extension tube). In that circumstance, I'll use a geared focus rail mounted on the tripod to achieve the fine adjustments needed. Sliding the tripod around results in too gross an adjustment. I never move the camera to focus on a pen.
I agree. Tethered shooting (especially with live view) is incredibly useful for small product photography. It is much easier to see (and therefore correct) problems in a photo when displayed on a computer monitor than when viewed through the viewfinder or on a camera's display screen. Shooting tethered with my current camera, focusing is as simple as moving the mouse pointer to and clicking on the spot where I want to focus.
Maybe, but doubtful. The photo was shot with a shutter speed of 1/170 sec at a focal length of 18mm. That should be plenty fast enough to prevent camera shake (especially with image stabilization on). The aperture of f/4 and a distance of roughly 1.5ft yields a depth-of-field of about 1.3 inches, which is visible in the photo - The nosecone (and the front edge of the stand) is sharp, but the finial is slightly blurred. Focusing closer to the centerband would help, as would a smaller aperture. F/5.6 would yield a DoF of about 1.8 in and f/8 would extend that to 2.6 in. A 35mm camera (such as the 5D series) using an 85mm lens at f/22 would produce roughly the same field-of-view and depth-of-field as the G15 at f/4. A 5D at f/32 would yield similar DoF as the G15 at f/5.6.
