Control Lens Flare - Outdoor Photographer Magazine - May 2016 Issue
[The following is a feature article that appeared in Outdoor Photographer Magazine's May 2016 issue. It is reprinted in its entirety, along with the accompanying photos/exhibits.]
As landscape photographers, we are often entirely dependent upon available light from the sun. Without a doubt, the position of our nearest star can make a good image great, or it can make an image look flat and mundane. Furthermore, pointing your lens directly toward the sun can be a great compositional tool. It can also present a host of problems in the form of lens flare. While lens flare can be used creatively and effectively, particularly with portraiture and wedding photography, it often produces unwanted distractions in landscape photographs. Luckily, there are a number of techniques we can employ in the field and later in post-processing to salvage unusable images, and to elevate good images to a professional level.
Field Techniques
Before we dig into post-processing, let’s talk a bit about what causes lens flare and what can be done to control it in the field.
Simply put, lens flare is caused when direct sunlight enters your lens and reflects between the lens elements prior to hitting your camera’s sensor. This can have two effects, depending upon where the sun is relative to your lens. If the sun is shining on your front element but is outside your lens’s field of view, the resulting image will suffer a loss of contrast; shadows will be washed out, and highlights will appear hazy. The folks down at Adobe just added a handy Dehaze slider in the Effects Panel of Lightroom that deals with this issue nicely. Alternately, if you are shooting directly into the sun and the sun is within your lens’s field of view, the resulting effect is an appearance of one or more polygonal splotches of various colors.
So, what can we do to tame this phenomenon when capturing a brilliant sun-star or a strongly backlit scene? There are a couple of things. 1) If it’s within your budget, purchase lenses with anti-reflective coatings. Nikon’s Nano Crystal Coat and Canon’s Super Spectra Coating were developed specifically to improve light transmission and decrease flare; the other major lens manufacturers have their versions. 2) Avoid using filters. Polarizers lose their effect when shooting straight into the sun anyway, and with Photoshop’s advanced blending capabilities, you can leave that split-ND in your bag. If you must use a filter of some sort, pay the extra money for a coated one. 3) Make sure your front element and any filters are free of dust and fingerprints. 4) Use a lens hood when the sun is outside your lens’s field of view; you can go a step further by shielding the lens with your hand or a fold-up reflector. 5) Use prime lenses if you have them. Incidence of lens flare is largely dependent upon the number of glass elements inside your lens; since zooms by design have more elements than primes, they are more susceptible to flaring.
Once each of these considerations has been addressed, use your camera’s Live View function to preview any problem spots within your image. When possible, I always try to position residual lens flare in a low-contrast or low-detail area that will be easier to fix in post-processing.
Alas, despite the precautions you may take during capture, unwanted lens flare cannot always be completely eliminated in the field. For these situations, I’ll outline the three post-processing techniques I’ve found to be most effective in my own workflow.
Fig. 1
Cloning / Healing
Depending upon the amount of lens flare you’re encountering and its position within the image, it’s sometimes possible to get away with a simple correction using the Clone Stamp or Healing Brush tools in Photoshop. This technique comes in handy when you have only a few small problem spots in areas not rich in detail, such as the tree trunk in Fig. 1. A good rule of thumb for remembering when to use the Clone Stamp versus the Healing Brush is that the former works well along distinct edges, while the latter works better away from them. This is because the Clone Stamp tool, as its name would imply, uses a pixel-for-pixel copy of its sample area; the Healing Brush, on the other hand, blends color information from the sampled area without copying exact details, like edges. (Try using the healing brush along a distinct edge, and you’ll often wind up with a discolored smudge.)
The tree trunk in Fig. 1 had three distinct problem spots, but took less than 30 seconds to fix using the Clone Stamp and Healing Brush tools. The first two spots were far enough away from the edges of the trunk that a quick fix using the Healing Brush worked splendidly. The third spot, situated right along the edge of the trunk, was a good candidate for some careful cloning. It can take some practice to maintain consistency when cloning along edges such as this one. Always make sure you are working on a separate layer from your Background, and set your tool parameters to sample layers “Current & Below.” Experiment with each tool, sampling areas just above or just below the problem spots, and paint over the offending lens flare until you are satisfied with the result (see top of page). Easy!
Exposure Blending
The Exposure Blending method of removing lens flare involves equal parts fieldwork and post-processing. This procedure works well when the sun is present in your composition, as is the case in Fig. 2. To begin, make sure your camera is locked securely on a sturdy tripod, as this procedure won’t work (or will at least be prohibitively difficult) if your captures don’t match completely. Make two exposures: one with the sun present in the frame, and another in which the sun is blocked by your finger (Fig. 3). It’s a good idea to manually set your white balance so that your colors don’t change when the sun is covered up. You may also want to expose a half-stop or so brighter for your second frame, as blocking the sun can globally darken your resulting capture just a bit. Your camera’s histogram can come in handy here.
Open your two files in Photoshop. Your first capture, in which the sun is visible, will be your background layer. Copy your second capture, with the sun hidden, and paste it over your Background as a new layer (Photoshop will automatically call this Layer 1). Add a black layer mask to Layer 1 by going to the Layer menu, dragging down to Layer Mask, and selecting Hide All. Since black = hide and white = show in Photoshop language, your black layer mask will hide Layer 1 from view. Next, select your brush tool, and set your foreground color to white. Making sure that your black layer mask is selected in the Layers Panel, begin painting white in the areas of the image that currently exhibit lens flare. Watch as the offending areas disappear!
Fig. 4, 5, 6
While exposure blending is a powerful method for controlling lens flare, it can take some practice. Often, your two source photographs will have slight variances in exposure or color due to adding and removing a light source as powerful as the sun. Experiment with Levels, Color Balance and Exposure adjustment layers and masks in order to fine-tune your blended image (Fig. 4).
Frequency Separation
Frequency separation is a technique that has become popular amongst portrait photographers because of its ability to edit fine details (high frequencies) and color/luminosity data (low frequencies) separately during retouching. For landscape photographers, the method can be used to control lens flare in areas of high detail, like the hot spot on the rocky hillside in Fig. 5.
Fig. 5
To begin, copy your background layer twice. Photoshop will automatically call these “Layer 1” and “Layer 1 copy.” “Layer 1” will be your low frequency layer, and “Layer 1 copy” will be your high frequency layer (I like to rename the layers accordingly). Make your high frequency layer invisible by clicking on the eyeball icon to the left.
With your low frequency layer selected, select Filter>Blur>Gaussian Blur. Move your Radius slider back and forth until you find a setting in which your photo is still recognizable, but all fine details are gone. For this particular photo, I set my Radius to 20.
Fig. 6
Make your high frequency layer visible again; then, with that layer selected, go to Image>Apply Image. The Source box should show the name of the file you’re working on. From there, match all of your settings to those in Fig. 6 and click “OK.” You will be left with a rather bizarre looking layer devoid of much color data. Above your Layers Palette, you will see a box with the word “Normal.” Click here, and select “Linear Light” from the drop down list. Counter-intuitively, your image will now appear normal again.
Select your Clone Stamp tool from the Tools Palette, and highlight your low frequency layer. Sample tonal areas near the offending lens flare and paint them into the discolored area or areas of your image. Because you are sampling low frequency color information rather than fine details, you will see that you can correct lens-induced hot spots such as these with little to no loss of image quality (Fig. 7).
Fig. 7
Practice Makes Perfect
Learning which of these techniques works best with a particular image only comes with experience and practice. Don’t be surprised if it takes some false starts and experimentation to get it right—I still start from Square 1 on almost every image. While there’s no Swiss Army knife that will fix each and every occurrence of unwanted lens flare, using the techniques outlined above will lead to more “keepers” and better photos!