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View Full Version : Idea for focus-recompose remedy?


Ook
29th of November 2008 (Sat), 12:40
(If this has been proposed before, please let me know. It occurred to me the other day and I'd like to bounce it off a few heads :))

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Hello everyone, I'm sure most of us have read all about why focus-recompose (http://visual-vacations.com/Photography/focus-recompose_sucks.htm) can be a bad idea because of the planar nature of camera focus systems. Locking focus on a point and then recomposing will shift the plane of focus such that the subject will inevitably lie just in front or behind focus. This is all due to the joys of triangles and exacerbated by using large apertures.

Now, those familiar with optical-IS-equipped lenses know that a floating lens element corrects a wobbling image by shifting to counter camera shake, which is picked up by gyroscopic sensors which direct the movement of the floating element via electromagnets. So, clearly we have the technology to detect minute movements and use that to adjust physical systems on a camera/lens.

Now, what I'm wondering, is shouldn't it be a reasonably simple matter to use the same sort of gyroscopic sensors to detect camera movement after focus has locked which would shift the focal plane to compensate for recomposition? Focus distance is known, the angle of movement is known, it seems to me that we have all of the information and technology to get around the focus-recompose problem. The IS lens' gyroscopic sensors could feed information into the AF system, which could automatically compensate. It seems to me that I can't get around the problem of recomposition, even if I were to have a 51-point AF.

Any thoughts?

SkipD
29th of November 2008 (Sat), 14:44
"Focus-recompose" is usually not a problem. In the "olden days" of film cameras, most 35mm cameras had some sort of focus aid in the center of the viewing screen - usually a split-prism rangefinder or a microprism spot or circle. We almost always used the "focus-recompose" method as a result of the tools available to us. As long as we didn't radically change the angle of where the camera was pointed (between focus and final composition positions) when shooting relatively close to the subject, the focus was almost always just fine.

Most of the experienced photographers in that era realized the potential for a possible focusing error but, as I said, the "problem" just didn't surface very often. Why folks make such a big deal about it today sometime makes me wonder. Could it be because those folks are "pixel-peeping" and looking at the images at a far greater size than they would ever be printed to?

Ook
29th of November 2008 (Sat), 15:16
Why folks make such a big deal about it today sometime makes me wonder. Could it be because those folks are "pixel-peeping" and looking at the images at a far greater size than they would ever be printed to?

Could be, or could be the popularity of super-shallow DOF? Thanks for the reply!