If you’ve ever wondered what the point of the little viewfinder cover that comes with most cameras is, or the viewfinder shutter that some higher end cameras have, you were probably told that it helps prevent light leaks. And then, if you’re anything like me, you probably dismissed that information as totally useless, since what are the odds that light would come through the viewfinder and affect your shot? But if you’re seeing weird purple or green flares in your long exposure shots, it might be time to revisit that idea.
For years, I had absolutely no issues with light leaks. Even when I was shooting on a tripod and didn’t have the camera to my eye, there was never any problem with my photos. However, this was before I picked up an ND (neutral density) filter.
Having read up on good filter brands, I picked up a good midrange B+W 10 stop filter. At over $100, it wasn’t a cheap knockoff, so I was shocked to see major flaring in some of my images taken with it. The photo above is a 5 minute exposure, showing the flare well. I figured there was nothing I could do, that must just be how these things work, and I took care to avoiding shooting into the sun and shaded the lens.
Frustratingly, the flare was completely unpredictable. Sometimes I took all the care in the world, and still ended up with a ridiculously huge flare in the centre of the images. Other times the sun would be right in the corner of the frame, and no issues.
I’d put the filter back for a few months, then pull it out for a day and be reminded of why I hate using it. It was such an incredibly frustrating experience that I was on the brink of springing for a much more expensive filter when I decided to do some serious testing to see if I could figure out how exactly the flare was being caused.
Going down to a nearby river, I started snapping shots with the filter on. No flare was visible, even when shooting into the sun. After a several test shots at different angles, I decided to pull out a tripod and take an image of the river.
Boom! Massive flaring, despite the sun being nowhere near the frame. In fact, the sun was behind the camera. This is when I clued in to the possibility of sensor flare. With the other test shots, my eye was to the viewfinder. But on the tripod, the viewfinder was exposed to the sun. So I took another shot, this time covering the viewfinder with my hand.
And violà, flare solved. Not only is there no ugly flare artefact, but the overall colour and contrast across the whole image is far better. So it wasn’t a filter issue after all, it was light coming in through the viewfinder! But why did I only notice it with the ND filter on?
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Lauchlan Toal is the creator of UnlockCreativePhotography.com, and a Halifax based food photographer. Outside of food photography, he enjoys most genres, finding fun in any kind of photography challenge.
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