Today’s Question: You talked about how you could figure out where lens flare would be positioned in a photo [in a recent Ask Tim Grey eNewsletter]. But how can I avoid lens flare altogether?
Tim’s Quick Answer: To avoid lens flare you need to ensure that the source of light causing the flare (such as the sun) is positioned behind the front lens element, or outside of the field of view of a lens shade. It is also possible to avoid (or minimize) lens flare by creating a composite image.
More Detail: Lens flare is caused by having a bright light source reflecting back and forth among the lens elements in a lens. A common cause of lens flare that is difficult to avoid, for example, would be having the sun in the frame of a photo.
You can mitigate the appearance of lens flare by changing your position, as noted in a previous Ask Tim Grey eNewsletter. Changing the zoom setting and lens aperture setting can also alter the lens flare, helping to minimize the adverse impact of the flare.
The best way to ensure there is not any lens flare in your photo is to ensure that any bright light source is behind a line parallel with the front lens element. In other words, having the sun more or less behind your position as the photographer. In addition, with the use of a lens hood, you can ensure the light source is outside the field of view of that lens hood, so that the hood effectively shades the front of the lens relative to the position of the light source.
Obviously either of the above approaches don’t provide ideal solution when then intent is to include the light source in the frame. In those cases you could create a composite image to minimize (or eliminate) lens flare in a photo, while still including the sun in the frame.
The approach involves first capturing the scene as you normally would, with lens flare included in the photo. Then capture a second capture of the same scene (ideally using a tripod to ensure the framing of both photos is a perfect match). For this second capture, use some object (such as a finger) to block the sun. This photo will not include any (or much) lens flare.
You can later combine the two photos into a composite, replacing the areas where lens flare is visible with the same areas from your second photo. This approach can alter the overall appearance of the image when there is scattered backlighting, for example, but does provide an effective means of minimizing lens flare in a photo.