Archived posting to the Leica Users Group, 2007/11/27
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Philippe Amard <phamard@numericable.fr> wrote: > how could reducing the angle result in a "larger" image is > the key to it I guess. It doesn't. Reducing the number of variables might help understand crop factors. Let's assume the only difference between two cameras is the physical dimensions of the sensor: both sensors have the same pixel pitch, bit depth, noise properties, etc. Same lens, subject-to-camera distance, everything else. In this hypothetical example the sensor with larger dimensions would have more pixels. Comparing a 4/3 sensor with a 24mm x 36mm sensor (so-called "full-frame"), the 4/3 sensor has a crop factor of 2, an angle of view half that of the "full-frame" sensor, and 1/4 as many pixels [ 1/(crop factor^2) ]. Comparing pictures made with the two cameras, the picture made with the "full-frame" camera will be identical to the picture from the 4/3 camera if the "full-frame" picture is cropped enough to match the angle of view of the 4/3 camera. The 4/3 camera's picture isn't larger; it has a smaller angle of view as though a lens twice as long (crop factor 2) were used on a "full-frame" camera. In reality comparisons aren't this simple because a lens designed for a 4/3 sensor can be optimized for this camera's smaller image circle requirements resulting in higher resolution, and a smaller sensor pixel pitch can put more pixels in the image area (sacrificing some noise performance at higher ISO settings) to take advantage of the 4/3 lens' higher resolution. IMHO adapting a "full-frame" lens to a 4/3 camera is less than ideal because, apart from the ergonomic isssues of fully manual operation on a camera not designed for it, the lens' central performance more often than not was sacrificed to some degree at the design stage for the sake of perfomance in the outer areas of the "full-frame" image circle. IMHO again, a more appropriate comparison of the two cameras would be comparing prints using optimum parts for each system using lenses designed for the camera it's used on with equivalent angle of view. Doug Herr Birdman of Sacramento http://www.wildlightphoto.com -------------------------------------------------------------------- mail2web - Check your email from the web at http://link.mail2web.com/mail2web