FWIW, some years ago one of the photo magazines tested 50mm enlarging lenses from all the sources at that time. The best overall was the 50mm f/2.8 EL-Nikkor. Here are the results - f/stop; center; edge (line pairs): f/2.8 40 25; f/4 45 40; f/5.6 80 65; f/8 60 45; f/11 40 30; f/16 25 20. All of the lenses showed a similar progression with best results 2 to 3 stops down from open as is commonly accepted.