Archived posting to the Leica Users Group, 1998/11/24
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 23:49 23/11/98 +0100, Erwin wrote : BTW: PopPhoto uses this Ealing measurement apparatus too. Most Lugmembers are not satisfied with or convinced that the popphoto results are meaningfull. So here we have at least four companies (popphoto, cdi,photodo, leica) using the same testing equipment. Why should we believe cdi or photodo while we disbelieve popphoto. It is not the equipment, but the smart use of it that generates useful results.The argument: they use Ealing, therfore it must be OK, is the same wrong inference as: they use Leica so the pictures must be fantastic. > >Erwin > ######### I have never used the argument : "they use Ealing, therefore it must be OK". An Ealing equipment is a sine qua non condition in order to have objective and significant raw data. Leica and Photodo publish such raw data in the form of graphs.I am not (exactly ?)Einstein but I can interpret a graph alone.After all it is my daily job. Now Chasseur d'images, Photodo and maybe Popular photo transform raw data into weighted means. That's the BAB of statistics.We can't criticize the method (using weighted means) if the method is clearly expose. That's the case with Photodo.But we can criticize the choice of the weighting parameters. You say :"Why should we believe cdi or photodo while we disbelieve popphoto". The answer is quite clear. Pop Photo does not give the method they use. Moerover there is a "subjective quality factor".What's that ? You wrote in a previous message about Photodo :"They give a very low weighting to in the field performance, the 40 lp/mm and the full aperture: this is precisely the area where Leica can score and excells. So their weighting for us Leica users is very uninformative".I partially agree with you. But they also publish weighted MTF at 40 lp/mm for f=1.4,2,2.8,4 and 8. I've compared their results for the Summilux 75 I own and I find them accurate, as accurate as CI results. BTW what is your own methodology ? Non weighting ? 40 lp/mm only ? Etc. Dominique Pellissier