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Filters and Digital Photography

Filters on compacts

Compact digital cameras don’t have filter threads on the lenses, so you can’t attach filters in the conventional way. There are two solutions. One of them is quick and dirty in the extreme – you just hold the filter in front of the lens when you shoot. It’s not easy to do this precisely with a graduated filter. The other alternative is to invest in Cokin’s Filterfast system. Here, the filter holder attaches not to the lens but to the tripod bush. An adjustable bracket lets you position the holder correctly according to the camera model, though you need to make sure you allow enough space for the lens to extend without striking the filter. It’s not particularly easy to work with a digital compact in this fashion and for those who use filters a great deal, a digital SLR is a far better option.

Exposure adjustments

It may be necessary to adjust the exposure when using filters beyond any automatic adjustment carried out by the camera. This is not always easy to predict, and depends on the filter and the conditions. Red filters for black-and-white photography, for example, require an exposure increase of around 2.5 stops, but the camera meter may not add as much as that, depending on the spectral sensitivity of the metering cell and the camera’s own metering algorithms. It’s important to take special care when using grads, too. Here, the best technique is to meter for the foreground, then add the filter, reframe and shoot. A simple point-and-shoot exposure with the filter in position may leave the foreground too light, depending on the strength of the filter and the brightness of the sky. After all, the intended result is often a net darkening of the scene, which a straight reading won’t always produce. As a rule of thumb, use a 2x grad on blue skies, 4x for overcast skies and restrict 8x grads for very large sky/ground brightness differences only.

Black & white

Convert colour to mono

Digital photographers have a choice – shoot in mono mode or shoot colour and convert to mono later. Shooting in colour gives you more choices later on, but shooting in mono helps you visualise the results more readily on the spot.

Red filter

Shooting with a red filter will darken blue skies and lighten yellow, orange and red tones in the image. This can give striking contrasts on sunny days. Heavy red filtration, though, can increase noise (the red channel is always quite noisy).

Green filter

Yellow and green filters are very popular with black and-white landscape photographers because they lighten vegetation and subtly darken blue skies, but without the exaggerated drama and contrast of a red filter.

Blue filter

To be perfectly honest, blue filters aren’t very good for mono work, but we’ve included an example here so that you can see the difference. This is similar to the results you’d get from old-fashioned orthochromatic (sensitive to all visible light except red) film.

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