When Markus Varesvuo went on a shoot with the Canon EOS-1D X Mark III on its release in February 2020, he decided to push the camera's capabilities to the limit. He wanted a technically challenging situation in which spectacular results depended not only on photographic skill, but also on the camera being capable of meeting that challenge.

As a wildlife photographer who has been specialising in bird images for more than 40 years, Markus knew that shooting birds of prey flying at high speeds can be tricky. What's more, if you're photographing species that are most active in the evening and at night, then the twin challenge of a fast-moving subject and very low light makes it difficult for any camera to capture them in sharp, high-quality, low-noise images.

So, he packed a kitbag that included a Canon EOS-1D X Mark III body, together with Canon EF 400mm f/2.8L IS III USM and Canon EF 600mm f/4L IS III USM lenses, and headed for remote forests in eastern Finland and Finnish Lapland in search of demanding subjects.

Here, Markus talks about the species he photographed, the obstacles he faced and how the kit performed in the field.

Which bird species were you aiming to photograph on your shoot with the Canon EOS-1D X Mark III?

"My main target on the shoot was the charismatic great grey owl. We searched in the woods in Kuhmo, eastern Finland, and managed to find some confident individuals. The goal was to test the camera's focusing and ISO capacity in challenging light situations, and also to find out how well the focusing could follow the super fast and erratic hawk owl in its flight.

"I travelled with fellow wildlife photographer Ville Heikkinen, who lives in rural Kuhmo and is very knowledgeable about owls. He knows the woods around his home like his back pockets, and if there are owls to be found, he finds them. It took us about a week to find the owls, four altogether, and we were able to work with three of them."

Which lenses did you use and why did you choose them?

"The Canon EF 400mm f/2.8L IS III USM is perfect for low light conditions and very fast in focusing. The Canon EF 600mm f/4L IS III USM, combined with 1.4x and 2x extenders, is excellent for shooting skittish birds that are easily spooked, because you can keep your distance and still get the shot."

How does the Canon EOS-1D X Mark III compare to the EOS-1D X Mark II you've been using, and what are the features that will help you get better wildlife images?

"At high ISO settings, the images from the Canon EOS-1D X Mark III are more than one stop better than those from the Mark II – perhaps one and a half stops better, which is a lot. This helps you shoot in low light conditions. The images are also sharper and the colours more natural.

"The battery also lasts much longer compared to the Mark II. I didn't have many chances to gain experience with the AF in difficult situations, but it seems to work very well, especially using the 30-point Zone AF.

"I mainly shoot through the optical viewfinder with the mechanical shutter, and like this the Canon EOS-1D X Mark III is able to shoot 16fps. This is two frames per second more than the EOS-1D X Mark II, which is important in action photography. The buffer is also almost endless. Needless to say, this is very useful in wildlife photography, where action situations can't be re-shot."

Did you use the camera in Live View to shoot the birds in flight at 20fps?

"With long lenses you have to shoot using a tripod or, if in a hide, a video head attached to a shelf inside the hide in order to use Live View. In certain special cases it seems to be a promising feature to use. One example is a case when I was in a hide shooting golden eagles, and two magpies started to mob one of the eagles. The eagle made mock attacks towards the magpies to chase them off. In this situation 20fps is fantastic. And the silence of an electronic shutter is a big advantage."

What was the maximum ISO you used? And what were the images like at that ISO?

"The maximum was ISO51200 and with careful postproduction the results were surprisingly good for such high ISO. With ISO16000 the results are very good. I processed the files using Canon Digital Photo Professional software. It is very good at handling the high ISO noise – better than other RAW converters I've been using."

Will the Canon EOS-1D X Mark III be your camera of choice in the future?

"I've been super happy with the EOS-1D X Mark II but, when there's a camera that's even better in almost every respect, I must say I'll be changing to the Canon EOS-1D X Mark III. I was really impressed by the file quality at high ISO settings. Every feature that's important for a bird photographer has taken a significant step forward in the Canon EOS-1D X Mark III."