Which colored filter should I buy first for black and white film?

A yellow filter. It darkens blue skies just enough for clouds to separate naturally, lightens skin flatteringly, and costs only about one stop of light. The effect looks natural rather than obviously filtered, which makes it the ideal all-round first filter before you move to orange or red for stronger drama.

Do coloured filters do anything on colour film?

Strong contrast filters like yellow, orange and red are meant for black and white film and will give colour film a heavy colour cast, so they are not used the same way. Colour film uses different filters, such as warming, cooling and polarising filters. The sky-darkening trick described here is specific to how black and white film translates colour into grey.

Colored Filters for Black & White Film

Black and white film sees colour as a range of greys, and often the wrong greys. A single coloured filter over the lens is the classic way to take control of that translation.

One of the quiet frustrations of black and white photography is that a dramatic blue sky with white clouds often renders as a flat, pale grey with clouds that barely show. The reason is that panchromatic black and white film is quite sensitive to blue, so a blue sky records almost as bright as the clouds. Coloured filters are the elegant, decades-old fix. By blocking some wavelengths and passing others, they change how colours translate into grey, giving you real creative control over contrast and tone.

How the filters work

The principle is simple: a coloured filter lightens objects of its own colour and darkens objects of the opposite colour. A red filter passes red light and blocks blue, so red objects go lighter and blue skies go darker. Every filter costs you some light, measured in stops of exposure called the filter factor, which you must compensate for unless your camera meters through the lens.

The four essential filters

Yellow: the gentle, everyday filter. It darkens a blue sky slightly so clouds separate naturally, with a look most people read as simply correct. Costs about one stop. If you own one filter, make it this.
Orange: a stronger version. Skies go noticeably darker, clouds pop, haze is cut, and skin blemishes are reduced because red tones lighten. Costs roughly two stops. A favourite for landscapes and portraits alike.
Red: the dramatic choice. Blue skies go nearly black, white clouds blaze against them, and haze all but disappears. The effect is bold and theatrical, sometimes too much. Costs around three stops.
Green: lightens foliage and renders it with detail, and gives more natural skin tones in some lighting. Useful for landscapes heavy with leaves. Costs about one to two stops.

Effect on skies and clouds

This is where filters earn their keep. Ranked from subtle to dramatic, yellow gives a natural sky, orange gives a bold sky, and red gives an almost stormy, near-black sky. Note that all three only affect blue sky — an overcast white sky has no blue to darken, so filters do little on grey days.

Effect on skin and portraits

Human skin contains a lot of red and orange. A yellow or orange filter lightens skin and softens the appearance of blemishes and freckles, which is generally flattering. A red filter can make skin look unnaturally pale and can wipe out texture, so it is rarely used for portraits. Green shifts skin toward a slightly darker, more textured rendering.

Choosing and using filters in practice

Start with yellow. It improves most outdoor scenes without looking obviously filtered.
Meter through the lens when you can. A TTL meter already accounts for the filter factor. With a handheld meter, add the factor yourself.
Do not stack unnecessarily. Each filter adds a light loss and a slight risk of flare and softness.
Match the filter to the sky. Bold red skies need actual blue sky and sunshine to work; on flat overcast days they do almost nothing.
Buy quality glass in your most-used thread size and use step rings for other lenses.

The filter factor in practice

Every filter has a filter factor, the multiplier by which it cuts light: a factor of 2 means one stop, 4 means two stops, 8 means three stops. A yellow filter is typically factor 2, orange around 4, red around 8, green 2 to 4. If your camera meters through the lens, the meter reads the darkened image and compensates automatically — but be aware that a deep red filter can fool a meter slightly, because film and meter respond differently to red, so many photographers give a red filter an extra half stop for safety. With a handheld meter you must add the full factor yourself every time.

Beyond the four: polarisers and ND

Two other filters belong in a black and white kit even though they are not coloured. A polariser darkens blue sky like a coloured filter but does it by angle rather than colour, so it deepens the sky without shifting the grey balance of other tones, and it also cuts reflections from water and glass. A neutral density filter simply reduces light without changing colour, letting you use slow shutter speeds or wide apertures in bright sun. Neither replaces the contrast filters, but together they round out what you can do in the field.

Materials, quality and mounting

Filters come as screw-in glass, resin squares in a holder, or gelatin sheets. Screw-in glass is the most convenient and durable for everyday use. Cheap filters can add flare and soften the image, so buy decent multicoated glass, especially the strong red and orange filters you will use in bright, contrasty light. Keep them clean and stored in cases, because a scratched filter degrades every single frame you shoot through it. Match the thread size to your most-used lens, note that number printed on the front rim, and use inexpensive step-up rings to fit one good filter to several lenses rather than buying duplicates. Store the filters in a small pouch in your bag so they are always to hand, since a filter left at home is a filter that never improves a single photograph, however good the glass may be.

Filters are a small investment that transforms black and white work, and Boston Camera stocks bodies and lenses with the standard filter threads you will want to use them on.