There are filters which are mainly used for black and white photography and filters which are primarily used for colour photography. It seems to me that you have the former type of filter. Here are a few comments on filters for black and white photography.
These filters lighten objects of their own colour and darken objects having a complementary colour. By way of examples
A red filter would darken a blue sky making it almost black and thereby greatly emphasizing white clouds. It can be used during the day time to simulate moonlight effects.
An orange filter would produce less exagerated effects darkening a blue sky to something like a mid gray whilst still emphasizing the clouds.
A yellow filter has similar effects on blue skies and clouds but the effect is much less obvious. Its corrects the natural tendency of film to render blue too light and thereby loosing light clouds.
A green filter renders greens lighter and helps to separate various shades of green in a landscape. This filter renders reds darker. It can improve portraits by slightly darkening lips and pinkish skin tones.
Most filters, all of them mentioned here, require the exposure to be increased. The amount of increase is given by the filter factor which is printed somewhere on the filter ring. This is only important when you set the exposure manually. If you are using auto exposure this will happen automatically.
|