It all depends on the photo and what you are trying to achieve. Macro shots with very shallow DOF will probably require more photos than a landscape image. You want your stack to include all the range that you want in focus with 30-50% overlap in focus from shot to shot. A good DOF calculator would come in very handy for this.
Sat 22-Dec-12 05:00 PM | edited Sun 23-Dec-12 02:02 AM by mklass
Pete's right, it depends entirely on the subject and your f-stop. For me a good rule of thumb is 5 shots for every inch of depth you want to achieve. That's using a 105VR at f/8 on something a foot to 18 inches of the lens.
It depends on the subject. I've used as few as 2 and probably as many as 14 or 15, don't remember exactly.
My focus stacking shooting is pretty much all done in the field so I don't do DOF calculations. I generally try to pay attention to the nearest and farthest points that I want to be in focus and manually change focus going through the range. You have to be careful with identifying the nearest and farthest points, it's easy to make a mistake. Needless to say you also have to be careful to overlap focus steps.
If you are using a tripod on a static subject then you should be able to do stacks with hundreds of images IN THEORY. The reality is that the more images you use the greater the likelihood of alignment issues and artifacts.
I've done up to 50 images with a handheld stack in CZP so using a tripod you shold be able to hundreds as long as your technique is sound. Sometimes with CZP you may also need to try several different stacking methods or reverse the images to get a useable stack.