-‘Light leaks you say?’ I’d heard that concept thrown around a few times. Mostly in terms of lo-fi instruments such as the classic Holga camera with its light leaks polluting the film in a, according to who you ask, either horrendous or rather pleasing manner.
Two years ago, when I bought my first and only neutral density filter, I would for the first time unknowingly experience this. I thought it was the unavoidable result of buying a cheap filter and did my best trying to avoid the colour cast in my post processing.
Parallel to this I’d several times heard people saying it’s important to cover up the viewfinder during longer exposures. My reaction would mainly consist of a smug smile while joking about long-winded and overly ambitious photography geeks. Time went and I decided to try this. My D800 has this brilliant feature where you with a simple click can cover up the viewfinder. Since it’s my only camera I can’t really photgraph it, but here’s how it looks in an image stolen by the help of a google image search.
A quick test at home with the inspiring subject being my bookshelf, I took two photos to try this out. One with the viewfinder open during a 30 second exposure, using my ND filter and trying to provoke light leakage with a flashlight; one under the same conditions but with the viewfinder closed. The results are quite striking.
I also redid the test without the filter and could not replicate the colour cast, so I do suppose there is a correlation with my ND filter. Having said that, I’m not entirely sure a 5x more expensive filter wouldn’t render the same effect.
I’m no engineer, but it is clear that somehow light gets inside the camera and lens-combination and creates an unflattering colour blotch when combined with a/my cheap ND filter. How to solve it? Remember to press that one button when I am doing long exposures out nearby bright lights.