The Heliopan 82mm Medium-Yellow #8 Glass Filter for Black and White Film is commonly used for a noticeable increase in contrast with black and white films. When your black and white images are flat, throw on a contrast filter.
Contrast in black and white is generally controlled by yellow, orange and red filters with red producing the greatest contrast. Moderate changes can be accomplished with yellow, which can generally bump up the contrast just enough to make the difference between a "muddy" print and an acceptable image.
Heliopan Lichtfilter-Technik of Munich, Germany, has changed their black anodized brass filter rings on most Heliopan non-rotating filters to their "slim" mounts. These slim mounts are made of black anodized brass stock and have so little rim in front of the lens (5.4mm) that they will not vignette with lenses as short as 21 mm.
Heliopan offers a wide selection of sizes, screw-in, series, bayonet, square and rectangular filters including digital, video, center weighted, graduated, wide angle, Kaesmann polarizers, drop-in polarizers, etc.
Especially useful for added contrast between blue sky with clouds and foreground.
Freckles and skin blemishes are diminished strongly, but lips are rendered more pale (to compensate for, you may use a dark lipstick).
Interesting for snow scenes under a blue sky, because the darkened blue shadows in the snow make the shapes of the landscape look more dimensional.
Filters still retain front threads for a lens cap, a lens hood or even stacking a second filter.
The portion of the Heliopan slim filters that are in front of the lens have been reduced in thickness by 37% over the former mount.
Heliopan cuts, grinds, polishes and coats their filters with the same techniques and equipment as used for the finest German camera lenses.