What are graduated ND filters... and why I never use them!
I often find that many students on my courses come along with a set of graduated ND filters (often referred to as ND grads), and are a little surprised when I tell them that I never use them! So today's subject covers what these filters are for, and the reasons why I don't use them and recommend that you don't.
What are ND grads?
Graduated Neutral Density filters are filters which are graduated from dark (which blocks light) to clear (which lets light through).
They can be made of plastic (cheaper) or glass (more expensive).
The standard ones (as pictured below) are dark at one edge and gradually lighten to clear in the middle.
There are also so called 'reverse' ND grads which are clear at the bottom, darkest in a band in the middle, and gradually lighter towards the top. This gives a clue as to what they are for!
They are fitted to the front of the camera using a square filter system, in such a way that they can be moved up and down in front of the lens.
What are ND grads for?
ND grads are designed for situations where you are taking photos of a bright sky above a darker foreground, often at sunrise or sunset where the sun makes the sky extremely bright.
The purpose of the ND grad is to help to lower the brightness of the sky compared to the foreground, so that the camera can better capture the dynamic range (range from bright to dark) between the bright sky and the dark foreground.
Reverse ND grads (where the darkest part is along the middle of the filter) are designed for situations where the sun is near to the horizon, when the brightest band in the photo will be along the horizon.
In theory, if the dark portion of the ND grad is positioned along the horizon, this should allow you to take well exposed photos at sunrise and sunset, without 'blowing out' (overexposing) the sky, or exposing for the sky and ending up with a very dark foreground.
So, why don't I use them?
The reason that I don't use ND grads is that in most situations they can cause more problems than they solve! For a very simple seascape, with a flat horizon they work well, however as soon as there is something sticking up from the horizon, e.g. a lighthouse or a headland, the filter will also artificially darken the top of these elements as well as the sky. In the photo below, I have used an ND grad to darken the sky; however, as you can see this has also darkened the top of the hill. An effect like this looks very odd and can be very difficult to remove in post processing.
What is the alternative to using an ND grad?
When I have a situation with a very bright sky and a darker foreground, instead of digging out an ND grad I instead use a technique called 'bracketing'. This involves taking multiple exposures of the same scene (at least one which exposes well for the sky, and at least one which exposes well for the foreground) and then combine these in post processing to produce a well exposed image of the whole of the scene. I will cover the topic of bracketing in a future email.
Want a learn more about photography?
If you're a beginner photographer who is local to East Devon and want to learn the art of landscape photography, check out my range of local photography courses. Alternatively why not make a weekend break of it and attend one of my residential photography workshops - either my beginners landscape photography masterclass for those starting out in photography, or my intermediate photography masterclass for those who already understand the basics and want more practical help progressing their landscape photography.