Light leaks often occur when using filters to achieve long exposures. Even though the shot is perfectly planned out, it’s a problem that requires a few extra steps to avoid.

The main reason to prevent them is that they’re nearly impossible to correct in post-processing. Other problems such as dust spots, hot pixels or color cast are easy to fix in either Photoshop or any RAW processing software but light leaks are a different story.

What Causes Light Leaks?

When light leaks through holes or gaps, and exposes the sensor to extra light, it leads to an unwanted glare or glow, typically around the edges of the image.

Unless your camera has been damaged, this is not a common problem for ‘regular photography’. However, it’s one that’s often seen in long exposure photography.

Luckily, there are simple solutions to eliminate the problem.

How to Avoid Light Leaks in Long Exposure Photography

The majority of light leak cases are caused by the light entering through gaps in the filter system or through the viewfinder.

Cover the Viewfinder

When I first began using filters to achieve a slower shutter speed, I was oblivious to the fact that you need to cover the viewfinderAt that time, there was a lack of online information on this particular subject and I struggled to figure out why my long exposures often had visible light leaks.

After a lot of research and talking with other photographers in the same boat, I learned that the solution was quite simple: cover the viewfinder.

Failing to cover the viewfinder will result in light leaking through it and reaching the sensor, causing glare and other unwanted artifacts, especially when the sun is behind you. The stronger the sun is, the more light leak you’ll see.

Several of today’s cameras’ come with built-in functions to block the viewfinder, but if yours does not, simply place a piece of dark cloth or paper in front of it while photographing. Alternatively, you can also purchase a viewfinder cover.

Place ND Filters in the First Slot

Note: This tip is only applicable if you’re using a square filter system

While you might not think so, the order you place the filters into the holder is important. Just a small gap between the filter and holder can be enough to result in unwanted light reaching the sensor.

Since light will leak through the first slot, make a habit to always place the Neutral Density Filter there to avoid it. Quite often, darker ND Filters come with a foam edge to block light from leaking through any gaps.

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

If your filters do not come with a light seal gasket, I strongly recommend purchasing some. Typically, these don’t cost more than $10 and they’re worth every penny. Just make sure they suit your specific filters.

Use Screw-in Filters

Unfortunately, the best square filter systems can be quite pricey and are not necessarily the place to start if you’re new to long exposure photography. Screw-in filters are just as good and despite having certain limitations, they rarely cause any light leak.

Since they are mounted directly onto the lens’ filter thread, you eliminate the probability of light finding a way to leak through.

Cover Gaps & Openings

The methods above should eliminate light leak but if you’re still experiencing it, the best way to find the source of the issue is by covering all gaps and openings with gaffer tape.

Try to cover every gap separately and take shots in-between to find where the light is leaking through. Don’t forget to cover the filter holder as well, as a poorly built system might be the reason you’re experiencing light leak.

Are you interested in mastering Long Exposure Photography? Then our Ultimate Guide to Long Exposure Photography is for you!

Find more Quick Tip Thursday articles here.