Thank you Calamity .... and yes you did answer my question about the plates you use. The plate size was very helpful. Also I didn't know if you were Japanning as opposed to painting them black. The former seems tough to say the least.
Robert, thanks for the info and web site.
Now I am off to order a roll of steel sheet metal.......
M.J.: the advantage of the weighing technique is that you have an immediate visual indication of the error in your measurement. Better, someone else (such as your thesis supervisor) also has an immediate visual record of the error in your measurement. With a planimeter you need to learn your own particular biases when tracing a shape, and other people just have to trust your numbers.
I used this technique as an undergraduate and postgraduate Physicist. During the course of my PhD (87-91) the availability and price of A-D convertor chips changed dramatically, as did the ways of gettnig the converted numbers into a PC. What was a neat trick became just another piece of technological history.
C.J. The reason to care about the curve shape is that many of the old C19th shutters have low 'efficiency' - they are fully open only for a short part of the shutter cycle. The plate doesn't care (if you ignore reciprocity failure at low light levels) but it can be worth making a table of 'real' shutter speeds verses marked, especially for the shutter's top speeds when working at full aperture. With a storage scope you'll see straight away how significant the rise and fall times are, and if they are so badly non-linear that you need to use something other than a simple 50% value. FWIW, if your scope can gang up several traces, it's a good way to see the repeatability of the shutter, which is probably more important than its accuracy.
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