Compare colour filters and exposure adjustments for black-and-white film

For an autumn walk with both sky and leaves in the frame, decide which colours you want to separate before you shoot.

What do colour filters change in black-and-white photographs?

Flowers and leaves that look distinct to your eyes can turn into similar greys in a photograph. A colour filter in front of the lens selectively passes different colours of light, changing the tonal separation between subjects.

ILFORD's colour filter guide explains that a yellow filter darkens blue skies, helping white clouds stand out. Orange produces a stronger effect than yellow, while red can increase the difference between sky and clouds further.

The table gives general directions for panchromatic black-and-white film. Panchromatic means the film responds to multiple colours across visible light. The strength of the result depends on the light, subject and film.

The ILFORD and HOYA official guides were checked on October 25, 2026. A stronger filter does not improve every scene. Check whether it will darken the subject you want to preserve.

Do filters of the same colour need the same exposure adjustment?

Adjustments vary by maker and model. HOYA's US guide specifies half a stop for its yellow K2, two stops for the orange YA3 and three stops for the red 25A. Do not apply those figures directly to other yellow, orange or red filters.

ILFORD's general guide gives a typical yellow filter a factor of two. A factor of two means twice as much light, equivalent to one stop of exposure. That differs from the half-stop figure listed for HOYA K2.

If you metered with the filter removed, apply the manufacturer's adjustment to that reading. You can admit more light by opening the aperture or extending the shutter time. Consider camera shake and moving subjects when the shutter time becomes longer.

Will the camera's meter compensate automatically?

Check whether your camera uses through-the-lens, or TTL, metering. Find the metering method in its manual and read the procedure for metering with a filter attached. A separate sensor outside the lens, or an external meter, may measure light before it passes through the filter.

Do not assume TTL compensates equally accurately for every colour filter. ILFORD points out limits to automatic compensation particularly with red and orange filters. Compare the camera and filter instructions before adding manual compensation to a reading already taken through the filter. Automatically adding it twice could give too much exposure.

Record the filter model, metering method and any extra exposure adjustment. After development and scanning, you can connect each frame to its shooting conditions.

What should you check before attaching a filter?

1. Check the film box and official documentation to see whether it is panchromatic.
2. Match the lens's front filter diameter and the filter's thread specification.
3. Find the exposure adjustment for that model and the camera's metering method.
4. Check composition, focus and shutter time before and after attaching the filter.

The official ORTHO PLUS description states that this film has no red sensitivity. Do not directly apply the table's red-filter effects or exposure values to an orthochromatic film like this. A black-and-white label alone does not establish the same spectral sensitivity.

If film types are confusing, start with the differences between colour negative, black-and-white and slide film. Before packing your camera bag, keep your filter's model name and its documented exposure adjustment together in your notes.