We see heat distortion used for creative effects in movies. For example, shimmering air that rises over a vast patch of parched land is a common shot in Westerns. And movie directors seem to love it.
However, for photographers shooting wildlife or landscapes, it leads to problems. Hazy or blurred images and problems with auto-focus systems pop up due to temperature differences in the air. Shooting with a long lens intensifies the issue.
In this article, we look at heat distortion as both a bug to be fixed and a feature to incorporate into your photography.
Contents
What is Heat Distortion in Photography?
Heat distortion occurs when sunlight passes through layers of air with varying temperatures. This leads to visual deformity in images. A common effect on hot days when the sun heats the ground which warms the cool air directly above it. This causes warm air to rise and creates a hazy or shimmering effect.
As light travels through these uneven layers of air temperature, it bends and refracts. This results in a blurred or wavy appearance in photographs, especially in scenes shot from a significant distance with telephoto lenses.
Why Does Heat Distort Light?
That’s the wrong question. It’s not just about heat. Light distorts when it passes through the air of different densities. Cold air is dense; hot air is less so. Light waves bend very little if the surface and air temperatures are about the same. So, that could be a cold day or a hot day. However, when cold air and hot air mingle, it results in gradients of air temperature. We experience this when we have a significant temperature difference between the air and the ground below it. And this results in visible heat waves.
What Causes Heat Distortion?
Environmental and physical factors, such as temperature gradients and air turbulence lead to heat distortion. As the sun warms the earth, the warmer air rises and cooler air descends. And this results in layers of temperature differences that bend the rays of sunlight, creating a wavy or shimmering effect, haziness, or a general lack of quality in images and videos.
The Impact on Image Quality
Various forms of degradation occur from heat distortion that affects the overall aesthetic of a photograph. Light passing through temperature gradients bends unpredictably, leading to a shimmering effect. These wavy lines disrupt the visual coherence of subjects in an image, creating an unsettling viewing experience.
Also, it may manifest as a hazy appearance, with details obscured and colors washed out. As the distance between the camera and the subject increases, it creates more room for temperature gradients and air disturbances that lead to these types of distortion. Heat distortion may significantly alter the perception of distance in photos and the effectiveness of visual storytelling.
Situations Where it is Most Noticeable
Extreme environments, such as deserts, asphalt highways, and expanses of grass are susceptible to heat distortion. In places where the ground or water temperature differ from the air temperature, cool and warm temperatures mix. And the light bends instead of passing straight through the air.
Photographers often encounter this effect during the midday sun when the heat is most intense. Layers of air with various temperatures refract light at different angles. As a result, distortions alter the perception of distance and the shape of the images.
Landscape and wildlife photographers confront this phenomenon frequently. Shooting their subjects with telephoto lenses over large expanses of open land exaggerates the effect.
Can Camera Settings Reduce Heat Distortion?
The answer to this: “probably not.” However, a fast shutter speed may minimize the visual effects caused by heat waves. That is, you simply expose the camera sensor to those heat waves for a shorter period of time. I’m not sure how you determine what shutter speed works best, other than testing it by trial and error.
Also note, a smaller aperture may enhance depth of field and improve overall image clarity, eliminating some haze. Or maybe not. As for ISO settings, I would recommend a range of 100-200 to achieve the lowest possible noise.
Can Camera Accessories Reduce Heat Distortion?
The answer here: “somewhat.” A lens hood, along with a UV filter and Polarizing (CPL) Filter won’t solve the heat distortion problem; however, these items help with other issues.
Ultraviolet and polarizing filters aren’t designed for this problem. However, when you shoot in conditions that produce heat waves and distortion, atmospheric haze is likely to be present as well. So, these filters help with overall image quality, even if they don’t eliminate it.
I recommend a lens hood in most shooting scenarios. It reduces glare. Of course, since the heat waves that lead to distortion accompany bright sunlight, a lens hood is a must-have accessory on hot days.
How to Avoid Heat Distortion
To prevent or minimize heat distortion, a number of measures can be taken. However, these techniques are not always practical and in some cases you just have to make the best of it. But here are some tips on how to avoid or work around it.
- Shoot when the sun is low in the sky. The air is coolest when the sun is closer to the horizon. If you plan your shots during the cool sunrise and sunset times, you minimize the degree to which photos are affected by heat distortion.
- Avoid shooting with telephoto lenses. Try another lens and get closer to the subject. That’s not always practical; at times you won’t get the shot without the telephoto lens. Still, getting closer to the subject mitigates the impact of heat distortion.
- Be aware of large expanses of land or water. Easier said than done. When you can, avoid photographing across an immense field or a large body of water. These situations are likely places where temperature gradients will be present, which affect your images.
- Don’t shoot across the hood of an automobile. It’s convenient to steady the camera on the car hood (bonnet for Britons), but a hot engine generates heat waves in the surrounding air. And those temperature differences lead to distortion.
- Shoot on cooler days. When the temperature of the air and ground are about the same, heat distortion is not an issue, or less of an issue. Also, overcast days tend to even out the extremes and are a good time to shoot.
- Change shooting angles. This may minimize the impact of heat waves, as different perspectives may reduce the effect. Incorporate physical barriers, such as walls, to mitigate the distortion. These techniques may work in some situations.
Working with Heat Distortion
It’s not always a bad thing. When it’s inevitable in your photography, consider embracing it as part of your aesthetic. The presence of heat shimmer or haze can add a unique dimension to images, transforming what might be seen as a flaw into a captivating visual element.
By integrating the effect into your composition, you create photographs that evoke a sense of atmosphere and distance. The effects can produce memorable visuals, offering a different perspective on the subject matter. When you explore new ideas, it’s all in how you do it.
Reducing the Effects of Distortion in Post-Processing
Most editing software cannot fully eliminate this visual effect. It is primarily a physical phenomenon caused by temperature differences in unevenly heated air. Generally, the best solution is to avoid heat distortion.
Some minor adjustments in post-processing may soften the effects and restore detail in the picture. These corrections require careful application and might not be effective in all cases.
- Sharpening. A slight adjustment to sharpening helps define the edges of images that appear blurred due to heat distortion. This is a sensitive adjustment. Too much makes the photo too sharp, which looks unnatural and introduces noise.
- Noise Reduction. Sometimes a slight noise reduction will smooth out the wavy appearance in a photograph. But, be careful. Too much noise reduction results in lost detail and the image will not be as sharp.
- Radial or Gradient Filter. These local adjustments can be applied selectively to areas of the image that are most affected.
- Dehaze. Lightroom and other software programs offer photographers this tool. It reduces haziness, especially in the background of photos. However, too much of the Dehaze function leads to over-saturated images.
Conclusion
A phenomenon caused by refraction as light travels through layers of heated air, heat distortion creates a shimmering or wavy effect in images. Most apparent in photos taken in hot climates, its impact can be substantial, leading to soft focus and loss of clarity. Photographers find ways to minimize the effect, work around it, or embrace it as part of the aesthetic in their photos.
I hope this article enhances your photography knowledge and helps prepare you to capture high quality photos. If you have any tips of your own, questions, or comments, please submit them in the space below.
Take Away
Photographers should understand heat distortion, its causes and how it impacts the quality of their images, especially when capturing distant subjects. There are techniques to minimize the effect as well as methods to integrate it into your artistic vision.
