Quote Originally Posted by Dan Fromm View Post
I've shot USAF 1951 targets with TMX at 1:10 and 1:20 with decent LF and MF lenses. I've never got much better than 50 lp/mm, put the difference between my results and Chris' and Kerry's down to operator error. Mine. Getting the best resolution possible isn't easy. I don't doubt their results even though I haven't been able to match them so far.
Iīm relieved that Iīm not the only one that can not achieve the lens test values of Perez / Thalmann. Theoretically you didnīt have the chance to get absolutely as high as the two since you tested at 1:10 where the diffraction limit is lower than at 1:20 where the two shot.

But the difference with about 10 lpm seems to be larger than the 1:20 and 1:10 effect could produce. So other factors may be to be involved.

I never could produce more than about 40 lpm on film with LF at any aperture. My highest values usually appear with f/22 and for my best lenses sometimes with f/16 or f/11.

I compared many lenses between 210 mm and 300 mm (Apo Gerogon, G-Claron, Symmar-S and some suprisingly sharp oldtimers as for instance a 210 mm Dagor). I used very high resolution Ortho films ORWO FO1, FO5 and ADOX / ROLLEI ORTHO 25. The last is said to resolve a maximum 320 lpm. I developed in Rodinal 1+200 and did not move the tray to much to get edge effects.

The sharpest lenses I tested where the 210 mm Symmar-S over a wide negativeīs area and the G-Claron that was surely not as good outside of the center like the Symmar-S. I shot at about 1:80 and did not use USAF chart, but could easily count lines from small details on that I had focused before shooting.

I assume that the most important factor that reduced my resolution were very, very small vibrations, since I did not use flash but daylight and had exposure times between 15 seconds and 2 minutes. My tripod is of wood that should reduce vibrations somehow. Wind could not influence my testing since I shot from a sheltered place.

(The best resolution I ever achieved where about 80 lpm in 35mm with an older (around 1970) 1.4 / 50 mm MF Nikkor in cooperation with Tech Pan developed in Technidol (if I remember the developerīs name correctly). The shooting aperture was f/4 or f/5.6 .)

Andreas