Don wrote: >The recent Kawai digital films have still been done with high speed >film, not with digital cameras. Digital CCDs are still very slow >compared to the special films. 13,500 frames per second is still beyond >digital, as far as I know. Speed isn't an issue now for high speed digital imaging. For $50K you can get a camera system that will do imaging up to 16,000fps in greyscale. For $150K you can get a maximum 100,000fps in colour. Resolution and field of view are more significant issues than fps if you're using these for data collection, as we are in our experimentation. Basic CCD resolution is of course fixed, and seems to be typically 1280x1024 pixels [market pressure went in the higher speed, moderate resolution direction]. This can be distributed over the field of view any way that your optics permits. Data is transferred in real time to a PCI buffer that is as big as your memory budget $ allows, but tends to fill up fast with megapixel frames coming in at ms rates. As the buffer fills it flushes the earlier data. You can choose what you capture according to whatever type of trigger system is best. There is a maximum data transfer rate which restricts field of view after some cutoff fps value. After that, each time you double fps you halve field of view to keep the pixels per frame the same. Being digital is nice because you can sync with actuation devices and other data collection signals, e.g. from force detectors, even add that information to the frames if you like. For qualitative observation of piano action behaviour 1000fps is generally ok - much of our imaging is done at that frame rate. Gives you one image per ms. Moving parts at 1m/s translate to 1mm/ms, so 1mm change per frame. My grad student has posted some cool movies of bubbles and droplets he took while learning how to use the camera.... http://real.uwaterloo.ca/~martinh/ >I had no idea. Are the Kawai tapes "top >secret", for Kawai use only, is there any access to them by technicians, >or do we get a chance to see them in Tennessee? What do you want to know? Stephen -- Dr Stephen Birkett Associate Professor Department of Systems Design Engineering University of Waterloo Waterloo, Ontario Canada N2L 3G1 Davis Building Room 2617 tel: 519-888-4567 Ext. 3792 PianoTech Lab Ext. 7115 mailto: sbirkett[at]real.uwaterloo.ca http://real.uwaterloo.ca/~sbirkett
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