I have a question about manual focus on dslr-like cameras. I have a finepix s100fs that is capable of full manual controls. The manual focus leaves much to be desired though as it is not a mechanical focus but rather a digital ring that basically acts the same way that a focus button would. I cannot push and pull focus the way older manual lenses can, it is more like a fine tune adjustment for the cameras focus.
For the most part this all works out well as I just set it to manual and keep an eye on it as I go, making adjustments to the focus as necessary. It has got me thinking though, what about when I want the focus to shift? The manual focus technically works, but it is not the easiest thing to manage so I have been playing with an idea that I think may be easier/more accurate.
Using a rack focus as an example, my thought is to switch from manual focus to the single auto focus mode. In this mode the camera does an auto focus for each shot, but I can place a target on my lcd screen as to where I want that focal point to be. So instead of manually adjusting the focus ring along the way I would just mount a focusing card on a track and arm of some sort, place my focus target on that card and move it in whatever the increments need to be for each shot...focusing on the card instead of the puppets. I could either place the card, focus, and then shoot, or just leave the card in the frame but place it somewhere that would be cropped out later.
Is this a workable sounding solution? It makes sense to me, but I am wondering if there are potential pitfalls that I am not considering.
It's a good idea - next step is to test it out. I'd love to see the results and hear how it works! One thing that comes to mind - this would work as long as you have open space to get your focus card in there, but as soon as you're getting close to your target (puppet's face or whatever) you might not be able to do that anymore and may have to switch to regular fly-by-wire focus again.
Of course, for a fast focus pull you'd only need 4 or 5 frames and can probably get away with just about anything - but if you want to do long slow controlled focus pulls that would be a lot more difficult.
Another possibility of course is to just have your start point, re-focus all the way to the end point of the focus pull, and then do a cross-fade dissolve between them. That would mean no animation during the fake focus pull - but it's just another tool in the arsenal to think about for certain situations.