This is for Hannah, and anyone else who has come across the casual way that a lot of togs talk about one or two types of filter that landscaper photographers use a lot: graduated filters and neutral density filters.
A graduated filter is one that is tinted at one extreme, and clear at the other, and the aim is to allow a subject that’s bright on one side and dark on the other to be recorded in a single image, controlling the contrast range. It’s a bit easier said than done.
I don’t use them much, and the first one that came to hand is the notorious Cokin tobacco filter. These were monumentally popular for about six months in the late Seventies, and have been unacceptable in polite society ever since. You can possibly see why – one apocalyptic sky is impressive. But hundreds… Not so much.
As the image of the camera shows, the filter holder allows the user to slide the filter up and down, and it’s also possible to angle it to allow shooting steep hillsides. It’s crucial to use depth of field preview to adjust the position, as the examples show.
The precise effect varies with aperture, focal length, and which slot in the holder the filter is in. Using a wider lens, a smaller aperture or a slot further from the lens makes the division between filtered and unfiltered sharper. Filters are available with greater or less strong tints, and with sharper and more gentle transitions between the two, and some people carry a variety. The good ones – high quality optical glass – can cost £100 each.
The purist filter is a grey one, altering tones but not colours – though often, there is a slight colour tint (especially for those using auto white balance, I suspect). Careful testing and experiment is wise before using one for an important picture!
Confusingly, many people call a graduated filter a graduate, which makes it easy to confuse with a measuring cylinder (also known as a graduate in some circles) or a person who has successfully completed a university degree…
And there are neutral density filters, too. These can be bought for relatively normal purposes, to deal with exceptionally bright light, or with a very high filter factor, to allow extended shutter speeds when the user wants to blur movement of clouds, water or anything else. A popular strength is ten stops, which turns day to night – but that is perhaps for another blog…
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