No, we’re not talking about capturing apparitions on camera, although some of the results might look like a ghost (hence the name)! Ghosting is a type of optic ‘oops’ that happens when a light source hits the glass element of a lens a certain way and produces some orb-like artifacts to appear in your image. Although these orbs might be kind of cool to trick your friends into thinking it’s a ghost, professional photographers are constantly grappling with preventing them!
As is true for any optical problem, the best way to eliminate or prevent ghosting from happening is to understand how they happen. In order to do this, we must go back to the beginning and learn about lens flare.
What Is Lens Flare?
As you can imagine, lenses are full of glass. All of this glass is intended to bend light. This action projects an image onto the camera sensor, therefore creating your image. Now, in the process of bending light, light bounces around all over the place. As glass is reflective, sometimes this bounce causes something weird to happen.
When light rays coming from a bright source of light reach the front optic element of a camera lens, in the process the light can reflect off of different lens elements, such as the diaphragm and the sensor. What happens is a streak of unwanted light across your image, which can degrade image quality and create unwanted objects in images. Even worse, lens flares can drastically reduce image contrast by introducing haze in different colors.
Is Ghosting a Type of Lens Flare?
Correct! Ghosting is one of the lens flares that can happen when light moves around too much. Ghosting appears in an image as an orb that wasn’t supposed to be there. These orbs of different colors and shapes usually appear in a direct line from the light source and can span the whole image, with dozens of different artifacts. This can be a major pain (if not impossible) to remove in post processing.
What Causes Ghosting?
The specific lens flare known as ghosting is caused by a strong light source being reflected repeatedly. You will most often encounter ghosting outdoors when the sun is lower in the sky (such as sunset or sunrise) and hits the lens at a certain angle.
Typically, the more glass the lens has, the more ghosts can appear. For example, a 70-200mm lens will have more ghosts than a 50mm lens.
How To Prevent Ghosting
Fear not, there are ways to prevent or severely reduce the likelihood for ghosts to appear in your image!
Firstly, when investing in a lens, look for lenses that have specialized glass coatings intended to reduce or prevent flares, which will include ghosting. For example, On Canon lenses, the coatings titled Air Sphere Coating (ASC) and Subwavelength Structure Coating (SWC) are intended to help with flaring.
As well as this, some lenses are better designed than others (outside of just the coating). For example, Nikon has been designing lenses with recessed front elements, which can greatly reduce flare and ghosting
Next, most lenses that you buy have a lens hood that comes with them. A lens hood is an accessory that snaps to the front of your lens, creating a literal hood around it. Each lens hood is shaped differently to match the characteristics of different lenses, and is intended to limit how the light hits the glass element of the lens. As a result, flaring is greatly reduced. If you don’t have a lens hood, you can use your hand as one by cupping the front of the lens right where the light hits it.
As well as this, be sure to clean and maintain your lens frequently- dust, debris, and dirt can all cause ghosting to happen as well.
Changing your perspective can also help, if your specific angle is causing too much ghosting, switch to a different position!
In conclusion, ghosting is quite annoying- but there are ways to eliminate it!