Can anyone who understands MTF charts help me with this? I've had a bit of a mental block with MTF data and I've only just realised that I, too, can understand and utilize MTF charts. I found an explanation here:
www.canoneos.com in the Glossary that made sense. Here is what it says about the actual charts themselves: > MTF charts display the lensı performance from center to corner. Running along the >chartıs horizontal axis, labeled 0 to over 20, is the distance from the dead center >(³0²) of a 35mm image along a diagonal line to the corner of the frame, which is >about 21.5mm away. On the chartıs vertical axis is a scale representing the degree of >accuracy with which the fine and coarse line sets are reproduced, in both the >sagittal (parallel to the diagonal of the film format) and meridonal directions. >Solid lines on the MTF charts indicate the performance of sagittal lines (parallel to >the diagonal of the film), dashed lines are for the perpendicular meridional test >target lines. So far, so good. This above explanation refers to two sets of lines; solid lines = sagittal, dashed lines = meridional. So for wide open and stopped down to f8 that gives two of each, ie two dotted lines and two solid lines. BUT- looking at the MTF charts on this site, ie clicking on "EF lenses" then on any specific prime lens then clicking on "MTF chart", this gives a chart that has two sets of solid lines and two sets of dashed lines in black, and then another two sets of each again but in blue. That's twice as many lines as I can find an explanation for. (And to keep this simple this is what I get from a prime lens- a zoom will have two charts for the focal length extremes, and I'm not talking about that- that I understand.) It looks as if the black sets, which are always lower than the blue and thus signify poorer performance, may be for the wide open data and if so blue sets may be the stopped down data. I'm probably missing something quite simple, but there are still twice as many lines than I can find explanations for in Canon's own explanation above. Unless of course there are two of everything, one line set for fine lines on the target and one line set for coarse lines on the target. If so, how can I tell which are which? Can anyone tell me how this works, with respect to Canon's own MTF charts? Joe B. * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
