A guide to ND Grads Filters and how to install them

15 June 2009, by Cican Alexandru

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Neutral Density graduated filters (ND Grads) are a necessary accessory for scenery photographers (landscapes, waterscapes etc). These filters help managing the contrast in high contrast scenes. The filter reduces the amount of light coming in from a bright sky for example, bringing back detail and the lost colour. Here is a photo I took earlier, to show you how the sky is displayed with and without the ND Grad.

http://tinyurl.com/kqxuqc

These filters are made of glass or plastic and they come in a rectangular shape. The bottom half is completely transparent, gradually transcending to a dark grey colour at the top of the filter. The idea is to place the dark grey part over the overexposed area of your scene (over the sky for example), bringing back the lost detail and evening the contrast.

Grad Types

There are different types of grads on the market. Grads are separated by two factors, their strength (known as density) and their transition type (soft or hard).

Density is measured in stops, with 1, 2 and 3-stop filters being the most common. Different brands refer to density in different ways like 0.3ND, 0.6ND and 0.9ND or ND2, ND4 and ND8. The transition refers to the length of the light-to-dark gradient. With hard grads the transition is sudden with a noticeable edge whereas with soft grads, the transition is smooth.

Usually when the horizon in a scene is invisible or broken you would use a soft grad and if the horizon of a scene is well defined, you would use a hard grad.

Brands

There are two main brands manufacturing the best grads, Lee and Cokin.

Lee filters are hand-made to a superior quality and their large size makes them ideal for wide-angle lenses. http://www.leefilters.com/camera/products/finder/ref:C475674155E58E/

Cokin filters on the other hand, are separated into four ranges. The A and P series are appropriate for small digitals and SLRs and the Z-Pro and X-Pro series are appropriate for large format cameras. http://www.cokin.co.uk/pages/main.htm

Once you’ve decided which filter is best suited for your needs, you also need to buy a filter holder and an adapter ring (explained below). Many websites offer filter kits, which is a complete package of one or more grad filters, with a filter holder and an adapter ring and an affordable price.

Filter kits: Cokin and LEE

Installing the filters

To successfully take photos with filters, you need to get hold on a filter, and adapter ring and a filter holder. With Cokin filters, filter holders come in various sizes depending on the series of your filters.

Adapter Rings

Adapter rings come in various sizes to perfectly fit your lens. To choose a correct adapter ring for your lens, you need the diameter of your lens. To find out the diameter, check on the front of your lens; there should be a symbol like this one Ø and some numbers (Ø58 for example). You should then purchase and adapter ring that fits lens with Ø58 mm.

Fitting the Adapter Ring

To fit an adapter ring on to your lens, you have to screw the ring in, rotating it clockwise until it stops rotating. View the images below.

Installing the Filter Holder

To install a filter holder, it usually slots in over the adapter ring (Cokin filter holders). You hold the filter holder backwards and slide it in over the adapter ring. See the image below.

Now you should have your camera ready to accept the filters with the adapter ring and the filter holder already mounted on it.

Installing the filter

To install a filter, you need to slide it in through a narrow slot on each side of the filter holder. From there you can adjust where the dark grey part starts and ends by sliding the filter up or down. To take a correct decision, analyse the changes by viewing through your viewfinder.

The ND grad filter is now correctly installed and ready to be used! You can also rotate the filter clockwise or anti-clockwise, by rotating the filter holder, to match your scene.

To remove the filter holder, find the small bump on the back of your filter holder and simply push it forward lightly to release itself from the adapter ring.