Explanations of how to best use a filter for your pictures:
Neutral filter, that protects your valuable front lens from mechanical damage and dirt as dust, rain or scratches.
As PROTECT/P/SCHUTZFILTER, and additionally better contrast on larger distances through elimination of UV radiation.
As PROTECT/P/SCHUTZFILTER, and additionally more pleasant skin colours and warmer landscape colours, 1A type weak and 1B type a little stronger
Takes reflections out of non-metallic surfaces and gives you much more beautiful colours, for instance real blue in the sky and green or blue in the water and so on. Strongest effect at sunlight and in 90° position to your photographic subject. The effect can be graduated by turning the filter mount and it can be controlled in your camera’s finder. Depending on your camera model you might need circular type or can use the cheaper linear type.
Increased contrast and saturation in black&white photography.
As GELB/YELLOW but stronger
As GELB/YELLOW but strongest effect. For instance for dramatic effects as almost black sky with pure white clouds.
More pleasant skin colours and more beutiful green in landscapes, at Black&White photography.
Are for instance engraved with KR (from KR-3 to KR-15). On analog film they compensate too blue light, as for instance with snow or at the seaside at noon time. In digital photography they give you warmer colours up to extremely red pictures. The higher the number the stronger the effect.
Are for instance engraved with KB (KB-3 to KB-15). On analog film they compensate too red light, as for instance in rooms with bulb light, candle light; outside in morning/evening sun and so on. In digital photography they give you cooler colours up to extremely blue pictures.
Depending on the type used, FL filters compensate the unpleasing colours of neon light or fluorescent lamp.
ND/GREY/NEUTRAL DENSITY FILTER
Take away light, so that longer exposure times are possible even when light is bright.
Called for instance Soft, Softar, Softener, Duto, Imagon (Imagon mostly complete special lenses) and so on. The types with concentric rings are the more simple type, those with hammertone design and the Imagon type are the higher quality ones.
Close-up lenses (for instance NL, Close-up, Elpro, Macrotar, Rolleinar) are screwed into the filter mount of your lens and let you get closer to your subject, for closer views up to real macro photography.
Make a multiple ray star (usually 4-8 rays) out of every dot-shaped lit in your picture, for instance at night photography or glistening sea.
PRISM (Bollywood Style)
Show a multiple mage of your subject, either circular or parallel, depending on the filter type.
ANDROMEDA (Bollywood Style)
Show your subject blurred or otherwise strange, always with coloured effects, depending on the filter type.
Allow to picture your subject twice if you use multiple exposure mode, in a neutral way, either horizontally or vertically; by turning the filter 180° after the first picture.
Can be used for B&W and colour, both analog and digital. Many possible effects, too complex to describe here, please google or check specialized literature.
Allow to picture both a very close and a very distant part of your picture sharp on the same picture.