Cold Focus

For the last few years, starting sometime in December and lasting through the month of March, I receive email after email from folks asking me one basic question: why are my photos soft in the winter?

This is me sort of distilling things down here a bit. The actual questions come in a myriad of forms and angles.

“Is there something about a snowy owl that makes our camera not focus correctly?”

“I’m in Yellowstone and all my lenses stopped working – any ideas?”

Anyone who has spent time around snowy owls will attest to the almost magical like experience of being in their presence. And when I lived in Wyoming and Montana, I blamed a lot of things on the Yellowstone Super-Volcano getting ready to erupt and thus creating some sort of tear in the fabric of the universe – like the internet not working or the 2016 US presidential election. However, I can honestly say that neither are going to impact the functioning of one’s autofocus system.

And yet, both things do have something in common – believe it or not.

Come this time of year, from snowy owls to literally every species of bird or mammal you can find and photograph in Yellowstone, there is a common denominator that, for all intents and purposes, connects all the autofocusing mayhem and mishaps together: cold ambient temperatures.

It’s called physics.

In last winter’s issue of PhotoWILD Magazine, I wrote a feature article about some of the big obstacles we face during winter - compliments of the cold, the snow, etc. From problems with our autofocus systems to the issues that must be considered with color channels in camera, the idea behind this article was to wildlife photographers overcome some of the biggest problems we encounter in the winter months. As someone who spends months on end every year working in extreme cold, I have decades of experience learning about the challenges we face in the winter and how to overcome them.

One of those obstacles, one of those challenges, is soft out of focus photographs.

If you have ever experienced this phenomenon in the winter, it looks like something may be wrong with the equipment in your hand. Maybe the camera took a hit and the imaging sensor was knocked out of whack. Or maybe a lens has an internal element that was bumped out of place.

I’ll be completely honest here, when I first began to spend a considerable amount of time in cold weather photographing wildlife, I found myself having similar questions and experiences.

The very first winter I lived in the Greater Yellowstone Ecosystem, technically Jackson Hole, Wyoming, I ruined so many incredible photographic opportunities because of my ignorance on the physics behind all of this. Wolves, owls, rare opportunities with badgers in the snow, a handful of unique situations in the middle of total whiteout scenarios during blizzards. All of these were relegated to the oblivion of the trash can of my MacBook.

So, for those of you who have found yourselves frustrated in the winter, angry with equipment, cameras, lenses, swearing and cursing after what may very well be a once in a lifetime opportunity with once in a lifetime subjects, I want you to know I’ve been there. We all have. It’s part of the growing pains we all experience as wildlife photographers in the cold.

But before I dive into the why of it all, let me ask you a simple question:

Have you ever wondered why Sony and Canon build white lenses?

The reason they do this is to mitigate heat within and around the lens.

Our equipment are finely tuned pieces of incredible engineering. Given that the job of a telephoto lens is to magnify the world and help record light, the physics of light and how it behaves in the natural world is all apart of the engineering equation. And while those engineers can’t control nature, they can do their best to try and anticipate some of those problems and work to build a better mouse trap, as the saying goes.

This is why most telephoto lenses are white. The color helps to reflect heat because temperature does some pretty crazy stuff when it comes to light.

Hot and Cold Air Masses

When you have warm and cold air next to each other, funky things happen with light. Hot air has a lower index of refraction than cold air does. This is because hot, or warm, air is less dense than cold air.

You already know this part though. It’s why heat rises. But what you might not know is that this density of air changes how light passes through it compared to cold air.

Because hot air is less dense than cold air, light can pass through it more quickly and easily. And as photographers, as a group of people running around with boxes in our hands that “record” light, we need to understand this part.

Light always takes the path of least resistance when traveling. So, when you have hot and cold air next to each other, light, and therefore what we actually see, becomes distorted as it moves and changes directions to pass through the different layers of air. The light literally bends back and forth as it travels through these air masses.

When we take two different masses of air with two different temperatures, we get heat shimmers. The wavy like shimmer in this is caused by the fact that the hot air is attempting to rise while the cold air is sinking down through it. This doesn't happen uniformly. It's an uneven and chaotic battle between the different densities of air. And as light passes through it all, bending and twisting as it follows the path of least resistance through the less dense air, what we see are heat shimmers.

This is what creates “mirages” in the desert. This is what creates the weird distortion you see between thermoclines when scuba diving. It's what makes the road look like it has puddles on it from a distance despite blue skies. It's even why the part of your straw in the glass of water looks bigger and different than the part sticking up in the air. And this is what will absolutely ruin your wildlife photography in cold weather.

Still with me?

Heat shimmers are not just a cold-weather issue. Anytime we photograph close to the ground over any distance, we flirt with the possibility of shooting through heat shimmers – spring, summer, fall, and winter.

But here’s the clincher:

Anytime we go from a warm vehicle and suddenly find ourselves photographing in cold temperatures, we CREATE our own heat shimmers.

The Problem with your Vehicle

All that hot air in your car results in massive distortion of light as it comes rushing out into the cold air when your roll your window. If you then decide to stick your telephoto lens out the same window, in the middle of that mass of warm air rushing out, your photographs will be soft. Your focus will be off. The bending of the light as it passes through the two different air masses means your autofocus will fail and not even manually focusing in this situation will solve the problem.

Likewise, the heat rising up from the hood of your car as you slap that 600mm down to steady the lens and photograph a coyote mousing in the snow means you are recording light bending and twisting its way through a haze as it works to find its way through two uneven and chaotically unraveling densities of air.

At first glance the solution to this problem seems simple enough. When it's colder outside of your car than in, don't shoot from the window and don't use your warm car to steady your lens. But unfortunately, the problems don't stop there.

All that warm air of your well heated vehicle also finds itself trapped inside the lens hood of your camera when you suddenly jump out to photograph in the winter. The cold works like a lens cap as two thermal masses become locked up next to each other – the cold on the outside with the warm on the inside.

And when this happens, the results are the same as trying to photograph from the window of the car while shooting through the cloud of warm air mixing with cold: soft out of focus images.

This isn’t just a problem with warm cars though.

The Problem with Sunshine

While in Yellowstone last winter leading a workshop, I came across two bison on a snowy ridge with a nice background. The ambient temperature was -3° F/-16° C. But the sun was out, and the bison were warming up. And as a result, every single photograph was soft.

When I looked at the photos on the computer that evening, nothing was in focus. It would have been easy to get frustrated here in this situation. Nice light. Good subject. Great background. The bison were completely stationary as they stood conserving calories and enjoying the warmth of the sun. How did I mess this up?

Upon zooming in to 100 percent, however, it was easy to see that there was something off.

The bison themselves were so warm from the sun that they created a field of heat shimmers around them that you could literally see in the photographs – even at negative three degrees Fahrenheit outside.

It makes sense. Dark colors warm faster than light ones. So, you stick a dark colored bison in subzero temperatures then bath it all in sun and you get an animal that is warmer than the surrounding air. The result is heat shimmers.

As a rule of thumb, if the sun comes out in the winter and you find yourself reveling in the momentary warmth, heat shimmers are being created all around you - especially with dark subjects like bison or moose or even black bears (outside of the winter when not in hibernation).

On very cold mornings, without cloud cover, often it becomes nearly impossible to capture sharp images by 10am because there are so many heat shimmers. It's rising off the snow itself, off the trees, the backs of birds and mammals alike.

Although most people tend to think of heat shimmers as being a problem in hot climates, it’s an even bigger issue for photographers and cinematographers when working in cold climates.

Lens Hoods

But I think we should discuss this issue with lens hoods further. It's a big one and there's much you can do to prevent it.

So, what happens with the lens hood is that you end up with warm air getting trapped inside the hood next to your front element. As I mentioned above, the cold air sort of works like a lens cap for the hot air.

This does go away on its own eventually. All you need is for the lens and the hood and the air within to acclimate to the cold. But in the meantime, you’re recording light that is being bent and distorted. It’s not a huge mass of air that’s noticeable to the eye like what comes spilling out of your window, but you will definitely see it in the form of soft photos.

A couple years ago, several photographers decided to address this issue with lens hoods via YouTube videos. The result? For the last couple years I have seen more than a few photographers running around sans lens hood during the winter.

I’m not a fan of this. While everyone’s winter is different it would seem, mine come with things like slick roads, ice, deep snow, or even just a million things I could trip over or slip on and ultimately fall and break the very expensive front element of my lens - regardless of snow, ice, and latitude. For me, in the wild, off road, off trail, lens hoods are as much lens protection as they are shades and hot air traps. So, I leave them on for protection as I would rather replace a $500 hood than a cracked $3,000 front element that takes weeks or even months to get fixed.

Understanding the hood traps a pocket of warm air is important. And luckily you can do any number of things very quickly to remedy the problem.

Some photographers will just put their hand inside of the lens hood and move it around a couple times to push the warm air out.

As for myself, I simply take the lens hood off and then put it right back on again when I get out of your warm vehicle. This lets the hot air out instantly.

Ironically, the situation I saw last winter, with its never-ending barrage of blizzards and snowstorms, was photographers with big lenses, with lens hoods off, still sitting in their vehicles with 600mm lenses sticking out the window. They heard that lens hoods can make images soft in the cold. So, they took the lens hoods off. The only problem is that in this situation, so long as they're stayed in their vehicles and photographed out the window, nothing was going to help.

The Temperature of the Lens

If you have ever photographed in the tropics, or any place where you go from a cool air-conditioned room directly into the heat and humidity, you have likely experienced problems with condensation on your lens. The barrel, glass, and internal air within the lens is significantly cooler than what's outside and you end up with the beer can affect as a result. This is a fact of life we work around by opening camera bags and setting them outside at lodges while we get ready to leave in the morning. Given 20 to 30 minutes, the lens has warmed up and the condensation goes away.

No amount of wiping the front element of the lens fixes this problem with condensation. Neither does removing the lens hood. And that’s because the problem is the temperature of the actual glass, barrel, and air inside the lens itself. Not until the lens warms up to the ambient temperature does the condensation stop.

In the cold, we can experience the opposite problem. The glass, and air inside of the lens, warms up to the same ambient temperature as our vehicles. When we jump out of a warm vehicle and rush into the cold, however, no amount of expelling hot air trapped in your lens hood is going to cool down the front element of your lens itself or the air that’s inside.

Much like going from an air-conditioned room in the tropics directly into the hot and humid rainforest, it takes time for a lens to acclimate as internal temperatures begin to match external ones.

If you are photographing away from your vehicle, and have ensured the warm air has been expelled from your lens hood, yet you still find your photographs to be slightly soft, it's entirely possible that the issue then is the actual temperature of the lens itself. The heat from the front element is going to continue to rise and distort light until it acclimates to the ambient temperatures. Likewise, the warm air inside the lens is going to continue to create problems as light refracts between the cold air outside the lens and the warm air within.

This is one of the reasons I am not a fan of the "run-and-gun" style of photography where you drive around and jump out to photograph animals you see. While some situations demand this sort of approach, I would always prefer find animals at a distance, calculate how they are moving around their landscape, then set up and wait patiently for them to come to me. This allows time for equipment to acclimate to temperatures and it helps put animals at ease with my presence giving them the decision to approach versus me chasing after them.

If you are in a situation where you find yourself jumping in and out from hot to cold pretty regularly – say, several times over the course of an hour – then you can use a dry bag to trap cold air around your lens while you’re outside. Slip your camera and lens into the bag and ensure it’s as full of air as possible before rolling down the top and securing it.

Understand, however, this is nothing but a temporary BAND-AID. The waterproof drybag traps cold air around your lens and only slows the rate at which the lens begins to warm up again. If you are in and out of the vehicle pretty regularly, this can help keep your lens from reaching the temperature of the inside of your vehicle and therefore help mitigate issues with focusing. But once the air inside the bag warms up, the lens will then start to as well and it’s back to square one again.

Focal Length

This business with hot and cold air is only amplified by the length of lens you are using and is why you rarely see this effect with a wide-angle lens. The longer the lens, the more magnified everything is, the greater the impact heat shimmers will have on your photographs and focus. A 400mm lens is going to experience less problems with this than an 800mm, for instance. This isn't to say that a 400mm won't be impacted by temperature. Nothing could be further from the truth. It's just that an 800mm it will often appear to be even worse.

. . .

When you start thinking in terms of hot and cold air and what that does to light, you will begin to understand why sometimes you just simply cannot get a sharp photograph to save your life.

There’s a lot we can do to help mitigate this though.

Never shoot from the window of a warm car on a cold day.

Step away from your vehicle and don’t use it to help stabilize your camera on a cold day.

Make sure you get rid of the warm air trapped inside your lens hood.

Understand that focal length only amplifies the effect.

And if all else fails, consider the internal temperature of the lens itself.

I have spent the last decade and a half living and working in extreme cold during the winter. I have photographed and filmed in the middle of blizzards and when ambient temperatures dropped to minus 57 degrees Fahrenheit (that was brutal). And understanding a little of the physics behind temperature and light will go a long way toward helping you overcome some of the problems cold temperatures creates with photography this winter.

Cheers,

Jared

P.S. If you want to learn more about the challenges of photographing in the winter and how to overcome those problems, check out the Winter 2023 issue of ​PhotoWILD Magazine​ in the membership dashboard. A subscription comes with all of the back issues.

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