Almost all lenses you can buy come with a rigid plastic collar that fits on the front called a lens cover. Here̵7;s what they do, why they are important and when to use one.
Backlight protection blocks unwanted light
When you take a photo of something, the reflective light enters the camera through the front of the lens. The light rays pass through the various lens elements that work together to focus it on the camera’s sensor. If you have everything set up correctly, you will get a nice photo.
But a lot happens inside the camera. Modern lenses are not simple convex or concave pieces of glass. They are incredibly complicated composite lenses. Instead of a large glass, it is five or 10. And each of these does something to improve the sharpness of the image, eliminate various deviations or just make sure your photo is in focus.
The light rays also do not pass through the various glass elements unaffected. In addition to being focused and manipulated in the intended ways, there is a transfer loss. This means that less light makes it to the camera sensor than the amount that enters the lens, which is why cinema lenses use t-stop instead of f-stop.
And it is only for the rays of light that are reflected from the scene that you are trying to photograph. Light rays also hit the front of the lens from all other directions. The rays from more extreme angles are never focused on the sensor; they just bounce inside the lens and interfere with the quality of the photo. The two most obvious effects of this are lens stains and a washed, hazy appearance.
Lens spots are the streaks of bright light shown in a photo. JJ Abrams loves to use them in his films as an effect, but for the most part they are unwanted.
Haziness may be a little harder to detect, but the effect is no less desirable. In the picture above without the lens cap, you can see the colors and the contrast is a bit muted. There is also a bit of a strong flare in the lower right corner. The picture taken with the lens cap is only better.
What a lens cover does is simple: it shades the front element of the lens and prevents light from hitting it from the most extreme angles. It’s the same as shading your eyes from the sun with your hand when you try to see something.
Lens protection also provides physical protection
While lens covers are mainly for blocking light, they also provide a small amount of physical protection. For example, if you are shooting on a rainy day or near a waterfall, a backlight can protect the front of the lens from a few drops. It is not a replacement for an umbrella, but it can give you a few moments to get a shot before the lens is covered in water and unusable.
Similarly, if you hit the lens against something when you shoot at a hectic wedding or, even worse, turn it off from a table, a lens cover provides an extra barrier on the front. It may not save the lens from shattering, but at least the front elements of the glass will not be the first to hit the floor.
When to use a lens cap
In general, you should wear a lens cap at all times. They improve the quality of your images and keep your lenses a little safer with almost no balances. The biggest downside is that they add a bit of bulk and are cumbersome to pack.
However, the following are the only situations where you should not use a backlight:
- You want lens flare as a creative effect.
- It is windy and you are using a tripod (a sun visor can catch the wind).
- You shoot in macro and the light source is close to the camera. An anti-glare screen can cast a visible shadow.
- You use filters and the filter holder prevents you from attaching a lens cap.
In all other shooting situations, it is a good idea to use a lens cover if you have one. In the worst case, it will have no effect, but in the best case, it will save a shot.
Different lens covers
There are two main styles of lens covers: conical and petal shaped. Conical hoods are the simplest and most effective because they completely shade the front elements of the lens. However, if you use a wide-angle lens, the edge of the lens cap may appear in the frame.
Petal-shaped hoods are slightly less effective. However, they have strategically placed cutouts that do not appear in your photos, not even at the largest focal lengths.
A lens comes with a hood designed for it. It fits both forward and provides optimal shade. If you need to replace a lens cover, make sure you buy one with the same profile.
Tips for using a lens cap
The best advice is to put the hood on the lens and never take it off. However, situations can become difficult in the real world. Lens covers are cumbersome, bulky and another thing you have to take with you everywhere.
Here are some tips and tricks to keep in mind when using a lens hood:
- Do not forget: You can attach a hood to the back of a lens so that it takes up a little less space in your bag. Otherwise, store it in the camera bag. They are the kind of things that can get lost in a box.
- It makes your camera bigger and more obvious: If you are trying to keep things down or do not want to announce that you are a journalist, consider leaving the lens cover off. This can be especially important when crossing international borders.
- It only works on light sources outside the frame: If you take pictures directly in the sun or headlights, you will still get lens flare. A hood only stops rays from extreme angles, not the one you shoot from.
- It will not have an obvious effect, but there is no reason not to use one: Just because you have managed without a lens cover so far does not mean that your next shooter will not be the one where you need one the most.