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Understanding Lenses: Part I, and is the third in a series of lessons about camera lenses. Links to the others are at the bottom of the article.
If direct sunlight (or light from another source such as a street lamp) hits the front element of your lens, you will almost certainly get flare.
There are two types of flare. One is specular flare; circular blobs or streaks of light across the frame. You can see specular flare in the photo below.
The other is veiling flare, where light creeps into the shadow areas of your photo, reducing contrast in the darkest tones and decreasing sharpness and definition. This is more subtle and not always as noticeable as specular flare. An example where you might see veiling flare is in a portrait backlit by the sun. The opening photo to this article contains veiling flare.
Quick tip: Using the auto-levels or auto-contrast functions in Photoshop helps compensate for lack of contrast caused by veiling flare.
Flare is caused by direct light hitting the front of the lens (this is called ‘non image forming light’). This can happen with any lens, but wide-angle lenses are more prone to this than longer focal lengths because of their greater angle-of-view. The easiest way to prevent flare is to make sure that there is no direct light shining on the lens. There are several ways to do this:
A lens hood is an essential accessory for any lens. Some lenses, usually the more expensive models in the range, are supplied with lens hoods. For any other lens you will need to buy one separately. The instruction manual of your lens will tell you which lens hood to buy.
It is best to buy that particular lens hood if you can, or a third-party alternative that matches the shape and size of the recommended lens hood. These are often less expensive, although they may not be made quite as well. But for a lens hood build quality doesn’t really matter, as its main task is to keep light off your lens.
The above photo shows a Canon EF 17-40mm zoom lens with the lens hood it comes supplied with. This shape hood is called a petal lens hood and is common with wide-angle lenses. The cut away corners are designed to prevent vignetting.
This photo shows a metal third-party lens hood that I bought for my 85mm prime lens. The field-of-view of this lens is much narrower than the 17-40mm zoom, therefore the lens hood can be longer without causing vignetting. Longer lenses are better protected by lens hoods than shorter ones.
Lens hoods work by casting a shadow over the front element of the lens. Once you have bought a lens hood you should keep it on the lens whenever you take photos. Even if you think your images are flare free, it may be that there is a small amount of flare that you don’t notice until you view the photo on your monitor.
Lens hoods also have the benefit of helping protect your lens from accidental knocks and scratches – another reason to keep them on your lenses while using your camera.
If the lens hood isn’t enough to keep the sun off your lens, there are other techniques you can use:
If the camera is tripod mounted, you can shade the front element with your hand or a piece of card during the exposure. Just make sure your hand doesn’t appear in the photo.
Stand in the shade when you take a photo, if possible. This prevents the light from the sun hitting the front element of your lens. If you’re taking a photo of someone backlit by the sun, and there is too much flare, try placing them in the shade instead. If you also stand in the shade when you take the photo, you won’t get flare.
Use prime lenses. Prime lenses (if you have one) are less prone to flare than zooms. One reason for this is that they contain fewer internal lens elements. One cause of flare is light being dispersed inside the lens as it passes through the lens elements. The fewer elements inside the lens, the less likely you are to get flare.
Keep the lens clean. If your lens is dusty, dirty or greasy it will be more prone to flare. Anyone who has looked into the sun while wearing spectacles or sunglasses will appreciate this. Your vision is clearer if the lenses are clean. It’s the same for camera lenses.
Cleaning is easy. I use a blower brush to remove dust and dirt, then lens tissues with a lens cleaning solution to clean the element. Check your lens (and filters) regularly to make sure that they are clean. Shining a torch onto the front element is a good way to see if there is dust or grease otherwise invisible to the naked eye.
The debate about filters is ongoing and opinion seems to be divided about whether they adversely affect the quality of the image or not. I don’t think it makes much difference and use ultraviolet (UV) filters to protect all my lenses. I feel more comfortable knowing the filter is there to protect the front element of the lens from knocks or scratches.
I buy coated filters which help reduce flare. They cost a little more but for me it’s worth it. I keep the filter cases in my camera bag so that if I’m in a situation where flare is an issue (if I’m shooting into the sun, for example) I can remove the UV filter temporarily and store it. I can also remove the UV filter if I use a polarising filter, to avoid having more than one filter attached to the lens at a time.
Finally, don’t forget than you can use flare creatively. Sometimes it adds to the atmosphere of the photo. There’s even a Photoshop filter for those situations where you would like to add it afterwards. Thats how I created the flare in the above image.
These are the previous articles in the series. My next article will be about flare; exploring the causes, how to prevent flare and also how to use it creatively.
If you liked this article then take a look at my latest eBook, Understanding Lenses: Part I – A guide to Canon wide-angle and kit lenses.