Extending the shutter speed and capturing images using the long exposure photography technique can lead to some amazing images. However, as with any technique, there are additional factors you need to consider in order to avoid damaging the image.

There are several such factors when working with a slow shutter speed but an important one, that often goes under the radar, is light leaks. These commonly occur when using Neutral Density filters and are nearly impossible to fix in post-processing.

So, what exactly are light leaks and why do they occur in long exposure photography? How do you prevent them from ruining your images? Let’s find out.

What are light leaks?

Light leaks come in many shapes, sizes, and colors but are most commonly seen as an unwanted glare or glow that appears in the corners of the image. In extreme cases, they are seen as a large miscolored spot covering large parts of the frame. Such as in the example below.

Light leak in long exposure photography
Light Leak from using a Long Exposure

As you might see, light leaks such as this are nearly impossible to fix in post-processing. It’s something that needs to be dealt with in the field.

Light leaks are more common for long exposure photography. That means that it’s less likely you see them when using ‘normal’ shutter speeds. If, however, you see them for all your images, that’s an indication that your lens or camera is damaged.

The reason why we see them more commonly in long exposure photography is that we use darkened filters to achieve this slow shutter speed. This means we need more light in order to get a well-exposed image. But small holes or gaps can expose the camera’s sensor to additional light, which causes these unwanted artifacts.

Since it’s nearly impossible to fix these areas in post-processing, we need to eliminate the problem already in the field. Luckily, there are a few simple solutions that make sure you never see light leaks again.

#1 Cover the viewfinder

The viewfinder is the most common source of light leaks in long exposure photography. This is especially the case when you’re using Neutral Density filters to achieve long exposures during the daytime, or when you have a bright source of light behind you.

This is because the light that enters through the viewfinder is a lot brighter than what enters through the lens. Normally, when you’re not using a filter, the light is the same on both sides of the camera, which means you won’t see any glare. Now, there’s very little light that actually makes its way to the sensor via the viewfinder. Yet, the little light that makes it, is enough to cause the glare and miscoloring you now know as light leaks.

Recommended Reading: Why You Need to Cover the Viewfinder for Long Exposure Photography

Failing to cover the viewfinder is arguably the main reason you get light leaks in long exposure photography. The good news is that a lot of modern cameras come with built-in functions to block the viewfinder. These are known as viewfinder shutters.

Don’t worry if your camera doesn’t have them, though. Simply place a piece of cardboard, a dark microfiber cloth, or your hand in front of the viewfinder to prevent light from entering. Alternatively, you can purchase a viewfinder cover.

Note: This is not the case for mirrorless cameras as the Electronic Viewfinder doesn’t let any light through.

#2 Place Neutral Density Filters in the first slot

Filters are important in long exposure photography. More specifically, Neutral Density filters are essential in order to achieve slow shutter speeds that completely blur or obscure moving objects. There are a couple of different filter systems but more and more photographers depend on square filters.

These filters are placed into a filter holder that typically consists of two to three slots. You might not think that it matters what order you place the filters in but it’s actually a very important factor.

As I mentioned, light can leak through small gaps and produce glare. These gaps are exactly what you get if you don’t place the Neutral Density filter into the first slot.

These filters often come with a foam edge that prevents any gaps between the filter and filter holder. Obviously, this will only work if the filter is placed in the first slot so that the light-leaking gasket is pressed tight towards the holder.

Light Leak for Long Exposure Photography
All NiSi ND Filters come with a light leaking gasket

There are some filter manufacturers that don’t include a light seal gasket. If this is true in your situation, I strongly recommend purchasing some. These don’t cost much more than $10 and, trust me, they’re worth every cent.

#3 Use screw-in or circular filters

The square filter systems are popular amongst landscape photographers but this system is quite pricy and not always the easiest place to begin. In addition to being a more bulky system, they also are far more likely to have small gaps where light can leak through.

Neutral Density Filters Guide

Circular filters are mounted directly onto the filter thread of a lens. This further reduces the probability of light leaking through. They are just as good as the square filters but they are less flexible as it’s not ideal to use multiple filters at once.

#4 Cover gaps and openings in the lens or camera

The three methods above should eliminate all light leaks. If you’re still experiencing some, it’s a good indication that either the lens or camera is damaged. In that case, I strongly recommend contacting your local camera store and sending the gear for a service.

Before that, though, you want to locate where the light leak comes from. The best way to do this is to bring out the trustworthy gaffer tape. Cut off small pieces and tape the gaps and openings around the camera until you’ve located the source. Remember to cover one piece at a time while taking images afterward. If the light leak is still there, cover the next place and try again.

Don’t forget to cover the filter holder as well, as a poorly built system might be the reason you’re experiencing light leak.

Follow the steps above and eliminate light leaks in long exposure photography! Are you interested in learning more about Long Exposure Photography? Then you’ll love my eBook ‘Ultimate Guide to Long Exposure Photography‘.