While using long exposures in the field, have you ever captured a ghost within your photographs? While you may not be haunted by spiritual specters, objects in motion often appear transparent and obscured by blurring when the shutter is opened for an extended period of time. While some individuals aim to create dramatic results by obscuring their subjects, others find ghosts to be problematic. Photographer Mark Wallace explains why this effect occurs and what can be done to stop it:
Why do long exposures produce ghosts?
The most important principle to understand is the simple fact that shutter speed directly impacts the way in which the camera’s sensor records motion. When photographing an object in motion, your subject may only stay in one spot for a moment or two—not enough time to create a proper exposure. When the subject moves out of a specific spot, the camera continues to allow light to trickle into a scene. So, when dealing with movement around the frame, the camera will capture details of backdrops and surrounding details within the area once occupied by the subject. Hence the “transparent” look that’s unique to objects subjected to slow shutter speeds
What can be done to freeze ghosts?
Freezing an object in motion is not as difficult as it seems. All that’s required is a strong strobe or speedlight. Regardless of shutter speed, these tools can freeze motion because the bright light that’s produced is enough to instantly expose a subject in a fraction of a second. However, if the subject in question continues to move around, the transparent effect will still be produced; the ambient light that’s captured by the sensor will continue to record details in the spot once occupied by the subject.
Is it possible to utilize long shutter speeds without producing ghosts?
Absolutely. The easiest way to avoid ghost is to eliminate the ambient light within a scene. That way, the only objects captured by the camera’s sensor are those illuminated by the light of the flash. It’s also possible to mix ambient light and flash to create unique results without ghosting, so long as the subject can remain relatively still for the duration of the exposure. This is because the singular photograph contains two separate exposures from the surrounding ambient light as well as the powerful split second flash.
Once a photographer understands the proper ways to harness light and how incoming light effects an image, a window of opportunities is pried open. Freezing objects in motion as well as capturing motion blur each provide their own aesthetics. With a basic understanding of what each element provides and how it can be attained, figuring out which details to include or omit lies entirely in the artist’s power.
“To help you understand this, I have a normal glass here and some water. If you think of this water as light and you think of this [glass] as exposure, what you’re trying to do is get just enough light so that it fills up your glass all the way to the top.”
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