A49 prevents building up too much density at some rather contrasty working films. I like it for aerial films like Rollei Retro 80 or Superpan 200.
It might explain why I got very good results with medium speed films like Plus-X but no so good with Tri-X. It might also comes form my development time... I need to investigate further. BTW, I use the ADOX version which should be pretty similar the the Calbe version.
"The problem with photography is that it only deals with appearances." Duane Michals
"Only weak pictures need perfection." David Vestal