Joe-- The sets of lines are for two spatial freqencies, high and low. That is, test charts with closely spaced line pairs (lp/mm at the image plane) for the high frequency, and widely spaced line pairs for the low frequency.
The lower pair of lines are for the amplitude response to the higher spatial frequency, and vice versa. I think somewhere on the Canon site they mention what the two frequencies are, but then they failed to relate this to the lines on the charts. I don't have time to look for myself right now. The idea is to get an idea how good the overall contrast of the lens is (that's the low-freq set) and how well it resolves detail (the hi-freq set). Once again, the lines lower on the chart are for the hi-freq stimulus. ------------------------------------------------------------------- Javier -- MTF specs were never intended to be the sole indicator of lens performance. To be sure, you need to take into account additional factors; , geometric distortion (as you mention), evenness of illumination, and resistance to lens flare are the most important additional factors. (Color rendition, as apart from contrast, is IMHO a lesser factor.) Any possible single figure of optical merit would be a composite of measurments of all these factors; however, the relative importance you place on each of them would not be likely to match the weightings chosen by the inventor of the figure of merit. So the judgement of lens quality, even restricting it to optical performance, cannot in principle be one-dimensional. -------------------------------------------------------------------- BTW. Does anyone know if there is an industry standard test for lens flare performance? It there isn't, I think there could and should be. DGW * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
