The Rollei RPX 25 was tested in the latest issue ( III 2014 ) of the German magazine
PhotoKlassik . The tester
Henning Serger was obviously impressed by the film and according to the article he measured a resolution of 120 Lp/mm and an efective ISO of 20 - 40 . I don't know if you can get a copy of the Magazine in Canada but I enclose a link.
Karl-Gustaf
http://www.photoklassik.de/
Dear Karl-Gustaf,
thanks for mentioning my test report about the Adox CHS 100 II and Rollei RPX in the edition III.2014 of "PhotoKlassik".
And also thanks to all the others here for their positive comments about PhotoKlassik.
I've just discovered this thread incidentally. Due to lots of work my presence here is quite rare.
To answer the questions of the OP concerning resolution and grain of the RPX 25:
Well, as I am running a little test lab for lenses, film, developers, sensors I can give you test results of this film compared to all other films in this group of very fine grained, high resolution films.
Here we go:
First, some information about my test method: I am using several test patterns, and a resolution chart with an object contrast of 1:4 (two stops). That is an object contrast you can find in lots of details in your daily, normal photography.
With higher object contrast details you will get higher resolution values, and with lower object contrast you will get lower values.
Test camera is my F6, with MLU on, MC-30 cable release, 1/250s shutter speed, focus bracketing, Berlebach 3032 tripod.
Test lens: Zeiss Makro-Planar 2/50 ZF at f 5,6.
So the following resolution values give you the system resolution of the film and this lens in combination. With better lenses, you get higher values. And with worse lenses, you get lower values.
The first, lower value represent clearly separated linepairs per millimetre, the second, higher number is the resolution limit at which a contrast difference is still visible.
My standard test developer for the resolution tests is Spur HRX, because it gives very good sharpness combined with very fine grain, resulting in very good resolution.
Rollei Pan 25: 80 90 Lp/mm
Rollei RPX 25: 120 130 Lp/mm
Rollei Retro 80S; ISO 25/15°: 135 145 Lp/mm
Adox CHS 50: 90 100 Lp/mm
Ilford PAN F+: 110 130 Lp/mm
Adox CHS 100: 80 90 Lp/mm
Adox CHS 100 II : 100 110 Lp/mm
Adox Silvermax: 105 115 Lp/mm
Fomapan 100 : 75 90 Lp/mm
Ilford FP4+: 75 90 Lp/mm
Ilford Delta 100: 130 140 Lp/mm
Kodak Plus-X: 80 100 Lp/mm
Kodak T-Max 100: 135 150 Lp/mm
Fuji Acros 100: 115 130 Lp/mm
If you want even significantly higher resolution and better sharpness, grain, then go for:
Agfa Copex Rapid; ISO 25/15° - 32/16°; Spur Modular UR New developer: 165 180 Lp/mm
Adox CMS 20 II, Spur Modular UR New or Adotech II developer: 240 - 260 Lp/mm.
Grain:
Finest grain of all by a huge margin has Adox CMS 20 II.
Then Retro 80S follows.
A little bit behind the 80S on a similar level Rollei RPX 25, TMX, Acros, Pan F+, Agfa Copex Rapid are following. The differences between these 5 films are very small and not really field relevant. And the ranking can be a little bit different when different developers are used.
Then the discontinued Pan 25 and Delta 100 follow.
After that Adox Silvermax, which is the finest grained of the traditional ISO 100 films with classic cubic crystals.
And just for comparison:
Under identical test conditions, same test chart, same lens and aperture, the
Nikon D800 delivers 80 - 85 Lp/mm,
and the D800E delivers 90 - 95 Lp/mm.
And
Provia 100F: 120 - 135 Lp/mm
Velvia 100: 125 - 140 Lp/mm
Ektar 100: 90 - 105 Lp/mm (Provia and Velvia also have a bit finer grain than Ektar).
I hope these test results are helpful for you.
Have a nice weekend,
best regards,
Henning