Archived posting to the Leica Users Group, 2000/11/05
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I heard last week that APX25 was NOT discontinued?.....of course, I heard on here it was....anybody know the poop?.. I can't stand tech pan.....and I did spend lotsa time trying.. I prefer "conventional" slow film with full exposure and minimum development... Walt On Sun, 5 Nov 2000, Erwin Puts wrote: > Is there life after APX25? A scientifically conducted study by several > German authors in 1990 gave these results. Technical Pan had a resolving > power of 250 lines per mm and APX25 of 180 lines per mm. These were the > best. A step below these two were almost on equal footing: PanFPlus and > Tmax100, with a small finegrain edge for PanF. These data in another > notation. TP and APX could resolve details of a width of 4 to 5 micron. > That is the maximum definition for a lens like the Apo-Summicron-R 2/180, > which defines the practical upper limit for the moment. The recently > designed Leica lenses however will be slightly below this level (in the > region of 7 to 10 micron), where the PFP and TMX are located. Older Leica > lenses have a limit at 20 micron generally speaking. > My own comparisons (prints at 20x and microscope analysis at 100 and 400 > times enlargement) do indeed show a theoretical advantage of the TP and > APX25 emulsion.(Both however are challenged by the new BW film, I am > currently investigating). > For most situations, the PFP would be a worthy replacement of the APX25 with > the additional plus of a full stop more speed and it is a true speed of > ISO50. Because the APX25 has a fairly steep curve, the sharpness impression > is excellent. The PFP however has a moderately steep curve, giving a > smoother graded tonality. > The sharpness impression is a bit less, but even so an enlarger lens like > the Apo-Rodagon-N 2.8/50 would have to perform at its best to get this level > of detail on the print at 20x enlargement. > You could try to do a comparison shooting with some of your APX25 films and > the PFP to see where the differences are and how important they are. > For most of my purposes I can easily switch between APX25 and PFP. If the > problem is demanding I have TP with CC40 filter to compensate for the > enhanced red sensitivity. > > Erwin > >