I generally shoot it with a 25 red, which really makes it slow. But about no difference in sharpness
with or without the filter, except to the extent a filter is one more optical element in the lightpath,
and to the extent it might or might not cut haze. The problem with Efke 25 is the risk of edge fog
when changing the rolls. It is also rather fragile in development, though this doesn't generally apply
in simple tanks. Still, it's been a popular film and one would think there would be a demand for a
replacement product by someone. The formula is certainly old-school. Pan F is nice when the scene
contrast is more manageable, but way too much of an S-curve for real high-contrast work. And in
color, Ektar gives opportunities for roll film that I would have turned my nose up at not long ago.
Micro films have never appealed to me due to bland tonality. Still, roll film is a pain in the butt in the
darkroom compared to 8x10 or even 4x5. I only use it when I have to.