Why did my ND filter produce washed out exposures?

Question

So I bought a set of (pretty cheap) ND filters a couple of years ago and took them on holiday to Canada with me last year. I managed to get a couple of OK shots but most of them looked something like this (ignore the other general crappy attributes of this photo):

All the colour is washed out and there's almost no detail left which sort of ruined most of the opportunities I had to take some nice waterfall long expos in one of the best places to do so (sadface).

Since then I haven't really bothered using them as I just decided they were useless but I'm looking into long exposures using ND filters again and before I go wasting loads of money on a fancy new set, I'd just like to confirm whether this is just something I'm doing wrong or it's something that can be corrected in post (I've tried adjusting the temperature and tint but it doesn't help the washed out nature of the exposure).

Maybe it is just crappy filters? If so, does anyone have any recommendations for a good set that isn't going to cost me hundreds. Ideally I'd like another set of square filters so I don't need a new set for different thread sizes.

Answer 1

You've got the sun almost in the frame. This is causing huge amounts of veiling flare — light bouncing all around, reducing contrast. You'll get better results from a different angle, or at a different time of day. Did you have a lens hood? If so, positioning the camera so the hood can better do its job would help.

And, yeah, it probably isn't doing you any favors that these are cheap filters. The multicoating on more expensive filters is specifically designed to minimize reflections and to reduce lens flare. But, if you put them in less stressful situations, that won't be as apparent.

Answer 2

Why did my ND filter produce washed out exposures?

You're shooting straight into the sun with a dirty, unshaded, and flat surface on the front of your lens.

The image demonstrates all three classic types of lens flare:

• Veiling - General loss of contrast due to strong off-axis light sources, often caused by such light interacting with dust, particularly dust on the front of your lens. It's usually even worse when the front of the lens is dirty and flat.
• Specular - Those little bright spots that are the shape of your lens' aperture opening.
• Ghosting - A flipped and reversed reflection of bright light sources. Usually the light source is in the frame, but it can also happen if a light source (like the sun) is extremely bright (like the sun) just out of the frame. Again, flat surfaces at the front of the lens tend to make ghosting worse.

In addition, there may also be light leaking around the edges of your filter holder or rings and reflecting off the back of the flat filter.

How many filters were "stacked" on the front of your lens in this shot? - Michael Clark

Honestly can't remember but it may well have been more than one because of the brightness of the sun. - Andy Furniss

Using more than one flat filter, especially when shooting into the sun, will magnify the effect of flare as light bounces back and forth between the flat surfaces with an air gap in between them.

Answer 3

As well as flare from dirty lens and filter surfaces, I suspect your ND filter is producing a lot of scattering of light internally to the filter itself due to microscopic inclusions in the filter glass.

Try looking at it in bright sunlight from multiple angles and consider whether it looks clear and transmissive or whether it looks slightly cloudy, which some cheap glass does.