What is that thing? The Eyepiece Cap?

I am sure that after buying your new DSLR you checked the box and probably knew most items packed in there. A neck strap, a battery, a cap to protect your camera when there is no lens attached, and a little piece of plastic. This little piece of plastic is called the Eyepiece cap. In this blog I’ll explain what this little cap is used for.

Eyepiece Cap

An eyepiece cap for the Nikon D7100 (DK-5).

There are two pieces of glass in your DSLR through which light can enter the camera. The first one obviously is the lens. The second piece of glass is the viewfinder. The viewfinder is used to “see what the camera is seeing”. You press your eyes to the viewfinder whenever you take a picture. By doing so you block out the light that is trying to enter the camera from the back. The only way for light to enter your camera now is via the lens, this is exactly what you want.

Loenen aan de Vecht

A small village situated on the river Vecht (Loenen aan de Vecht). I pressed my eyes to the viewfinder and took this picture. Since my eyes blocked the viewfinder no light leaked into the photo.

There are however moments that you take pictures using a tripod, especially when longer exposures are desired. In case of longer exposures, you don’t want your camera to shake, that is why you are using a tripod, right? So you don’t look trough the viewfinder when taking the shot, only prior to choose your composition.


A long exposure of Vreeland, The Netherlands. A tripod is needed to make this 20 second exposure possible.

Because your viewfinder is not covered by your eyes, nothing prevents light from entering your camera’s body from the back. If you are using a shutter speed of only a second or faster, this probably won’t be a problem. However, for longer exposures this might become a problem! Light is only supposed to enter the sensor trough the lens. But since your camera’s body isn’t completely leak proof, light is still able to creep in and ruin your shot.

Eyepiece Cap

Yes, for long exposure the eyepiece cap is useful! A shot ruined by light leakage.

And that is where the eyepiece cap comes in! This little piece of plastic replaces the rubber skirt around your viewfinder and completely blocks it. Light leakages are now prevented and you are save to use long exposures during the day. Using this cap means that you need your display for composing and recomposing your shots, but that is useful anyway if you are focussing manually (and even for autofocus this is useful).

Eyepiece Cap

An eyepiece cap attached to a Nikon D3100.

I use a Lee Natural Density filter (the Big Stopper) to be able to use exposures of ten seconds and longer during daytime for artistic matters, so this piece of plastic is very useful to me! Have you ever used it?

Loenen aan de Vecht

Using a Lee Natural Density filter (the Big Stopper) I was able to shoot using a 10 second exposure. The eye cap prevented light leakage.

Is there an item in the box of your canmera that you don’t know the use of? Let us know in the comments and I might blog about that soon!

Thank you for reading.

Kind regards,


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