One of the most common problems that photographers face when shooting long exposure photography is the issue of ‘false light’ or ‘light leaks’ appearing on the photos.
It can be a quite frustrating experience to spend time on setting up your equipment, double checking the composition, setting the remote timer for a shutter speed of beyond 4 minutes. Next, you wait for the camera to take the shot and eagerly anticipate a glimpse of your new long exposure fine art, only to discover that there are fat light streaks all across the photo. With exposure times of several minutes per shot, the beautiful light in the golden hour will quickly vanish if you have to use several attempts before you get the shot that you want.
Light leaks are nearly impossible to fix in post-processing. The only solution is to fix it at the scene and take the shot again, so it is even worse to come home with a set of shots with light leaks that you didn’t notice while capturing the photo.
The good news is that if you are prepared, situations like this can be avoided if you remember the tips below to avoid getting light leaks in your long exposure photos.
Why Do You Get Light Leaks In Your Long Exposure Photos?
You get light leaks in your photos because the light that hits the camera sensor comes from other places than through the lens and ND-filters. Light leaks are strange looking areas or bands of color that across your photo. Especially landscape photographers or others using long exposure times in their photography, experience this.
Normally, with shorter exposure times this is not a problem, because the small amount of light coming from other places than through the lens, will not be strong enough to affect the image. However, with long exposure photography, this is different. The shutter is open for much longer leaving the camera sensor exposed to light impressions during all this time. Even a small amount of light coming from openings that it shouldn’t create very visible light streaks.
There is a crack, a crack, in everything.
That’s how the light gets in. – Leonard Cohen
How to Avoid Light Leaks in your Long Exposure Photos?
Unless you have a poorly built camera body, it should be fairly easy to avoid light leaks in your long exposure photos. As mentioned above the source for light streaks is that light enters the camera body and affects the sensor, from other openings than through the lens. This would usually be either from the viewfinder or through cracks in the filter mount.
Cover The Viewfinder
To avoid light streaks or false light in your long exposure photos you should make sure to cover the viewfinder eyepiece before pressing the shutter. All cameras with optical viewfinders are prone to false light entering the camera through the viewfinder. Some high-end cameras, like the Nikon D810, have an inbuilt viewfinder cover that functions just like a small viewfinder curtain, that you can open or close. If your camera doesn’t have this, you can opt for buying an external eyepiece cap for your DSLR camera so you can switch the current eyepiece to this, when doing long exposure photography.
Alternatively, you can use gaffer tape even though this might wear a bit more on the camera body around the viewfinder area.
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ND-Filter Types and light leaks: Square Slide In VS. Round Threaded Filters
The next place you would want to check to prevent light leaks on your photos is to make sure that false light isn’t entering the camera, through a crack or misplaced filter.
There are different types of filter systems when it comes to ND-filters that you use for long exposure photography. One popular system is the square filters that come with a mount and lens attachment rings so you can mount the same filters on lenses with different barrel openings or filter sizes. The other option is to buy separate the round filters that mount directly to your lens. There are pros and cons to each system.
The system consists of a ND-filter, a filter mount, and an adapter filter ring to attach the filter mount to the lens. This gives you several places where light can possibly enter the lens directly instead of entering through the ND-filter. I.e. most filter mounts on the market allows for up to three filters to be mounted on the same time. If you by accident place a filter in the middle mount instead of the one closest to the lens barrel, or if you slide in the filter skewed, you will get issues with false light. Some square ND-filters come with a foam gasket that you can mount along the edge of the filter to prevent light slipping between the filter and the mount.
A poorly designed filter mount will also allow for false light to enter between the filter mount and the filter. It will not be a big issue when the filter is only a few f-stops. However, when using 10-stop ND-filters you will soon experience the effect of strong light leaks. If you opt for a square filter system you should also make sure that the filter-mount is high quality. Note, you should also take note on which size of square filters you need to cover the lens with the widest barrel diameter/filter thread size (ø).
Round Screw-On ND-Filters
The other type of ND-filters are filters that screw on directly to the lens. This minimizes the places where the problems with light leaks can occur. You simply have to attach the filter correctly to the filter thread on the lens. If you mount it correctly and if the build quality of the filter is good, you should have no issues with false light entering through cracks in the filter thread.
I prefer this type of screw-on ND filters for my long exposure photography work, because it is very simple, even though I don’t have the flexibility of using the filters on multiple lenses.
When I used the square format filters, I had a lot of flexibility but found out that I actually never used it. All my long exposure photography was done using my wide angle lens. And most likely I will continue to use it in the future. So I don’t mind being locked to using a single lens for my long exposure photography work and therefore it makes more sense to opt for a ND-filter solution that limits the issues I will have with false light and light leaks. However, if you need the flexibility – opt for the square filter types in high quality.
Cover Any Ports and Openings
If you still experience issues with light leaks in your photos, you can try to cover any other openings or ports on your camera with gaffer tape. Even the filter mount or filter thread to just to rule it out. With a little experimentation, you will find the source of the issues.
Long exposure photography is a very rewarding type of photography, where you get a chance to enjoy nature in the most beautiful light while waiting for your camera to capture an amazing long exposure shot of several minutes. If you find that you struggle with light leaks in your photos the fun and enjoyment start to fade. However, if you remember to use the above tips to avoid light leaks you can easily overcome it for good.
P.s.: Another issue you might experience in your long exposure photography is small white dots on the size of a single pixel appearing in your image. This has nothing to do with false light entering your camera. This is instead hot pixels or burned out pixels that occur due to your camera sensor overheating because of the long exposure time. You can use the Remove Hot Pixel Noise Photoshop action to remove it effectively.