If you have experimented with long exposure photography, you may have seen light leakage issues in your images. For the uninitiated – your camera is a light tight body that is intended to allow light from one end only, and that’s the front of the lens. Light only enters when you press the shutter release. Normally, your camera wouldn’t allow light to enter through any other opening in the camera. However, unless you have a badly manufactured camera, there is typically only one source that could potentially harm your images, and that’s your camera’s viewfinder. Let’s talk about what you can do to mitigate light leaks during those long exposures.
The Source of the Problem
As I have pointed out, the chief culprit is the viewfinder. Being essentially a small optical path that receives light bounced off the prism and mirror inside the camera, it often does the reverse of its job too. Light enters through the viewfinder and bounces off the prism and mirror and then goes onto the sensor. Normally, you wouldn’t see this as a problem, but when you are taking long exposures, it can create major issues. This is not unique to digital cameras only, film camera have this issue too. However, compact cameras and those without an optical viewfinder do not suffer from this particular problem.
Some photographers find it hard to identify the source of the problem. Many complain that it is their ND filter that caused weird light streaks in images. If you have been thinking the same, perhaps it is time to revisit this topic again – you might find your ND filter to be perfectly fine! The problem in that case most likely lies somewhere else, specifically in the viewfinder.