On Fri, Nov 09, 2007 at 11:19:05PM -0500, [EMAIL PROTECTED] wrote: > allow must mean something will happen. > > I am curious if there is a formula for when perspective distortion will not > occur, or some focal length at which it will not occur?
You get perspective distortion when the camera is not pointed straight forward, so the sensor is not vertical. This is generally only a problem with short focal lengths - if you are using a 600mm lens, you'll usually be pointing it pretty close to horizontal (either that, or you're photographing the sky :-). The ideal solution is a tilt/shift lens, which allows you to vary the angle of the optical axis without pointing the camera up or down. Failing that, you either have to keep the camera pointed horizontally, and end up with a lot of foreground that needs to be cropped away (assuming you have a wide enough lens, of course), or get perspective distortion (and DOF issues). > As for barrel distortion, it seems to be depend on the lens. . . > Is that true, some wide angles have barrel distortion and some > do not? Or do they all to some degree? It does, indeed, depend on the lens. Eliminating all traces of barrel distortion is generally going to be expensive. Lens design is almost always a compromise balancing distortion, vignetting, maximum aperture, weight, flare, contrast, cost, etc., etc. > And anyone who wants to expound more on the difference between barrel > distortion and perspective distortion, too, feel free. In perspective distortion straight lines remain straight lines, but parallel lines don't remain parallel. In barrel (or pincushion) distortion straight lines become bent. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
