The Canon RF 400mm F2.8L IS USM and RF 600mm F4L IS USM are must-have lenses for professional photographers shooting sport, wildlife, news and aviation with Canon's 365bet体育投注_365bet体育娱乐场-app官方下载@ System range of full-frame mirrorless cameras, including the 365bet体育投注_365bet体育娱乐场-app官方下载@3, 365bet体育投注_365bet体育娱乐场-app官方下载@5 and 365bet体育投注_365bet体育娱乐场-app官方下载@6. Both lenses feature Canon's latest lens technologies and, for the first time ever, provide Canon 365bet体育投注_365bet体育娱乐场-app官方下载@ System photographers with a choice of two dedicated super-telephoto lenses.

Both lenses are closely related to their EF stablemates – the Canon EF 400mm f/2.8L IS III USM and the EF 600mm f/4L IS III USM. "These EF lenses were developed alongside the first RF lenses, so they share some of the same electronics, components and ideas," explains Mike Burnhill, Professional Imaging Product Specialist at Canon Europe. But the latest lenses benefit from key enhancements made possible by Canon's innovative RF mount. If you're a professional sports or wildlife photographer, here's why the Canon RF 400mm F2.8L IS USM and RF 600mm F4L IS USM should be your new kitbag essentials.

Compared to the 8-pin EF mount, the RF mount's 12-pin connection provides much greater communication speed and bandwidth between lens and camera. This has enabled Canon's engineers to deliver even greater focusing performance with the development of Dual Power Focus Drive.

The RF 400mm F2.8L IS USM and RF 600mm F4L IS USM also enable you to store two focus presets and jump quickly between them. This can be a real asset if you're shooting from a fixed position, such as the sidelines of a football match, because you can preset focus on two points on the pitch where you anticipate the action will be.

Along with the fast and bright maximum apertures of the RF 400mm F2.8L IS USM and RF 600mm F4L IS USM, both lenses feature Canon's optical Image Stabilizer (IS) system, providing protection against the effects of camera shake when you have to shoot handheld in poor light. And compared to their EF predecessors, Canon has been able to enhance the performance of the hybrid IS systems in these lenses, increasing the compensation from 5-stops to 5.5-stops.

"We get an extra half a stop with these lenses, and again that's thanks to the RF mount," explains Mike. "The DIGIC image processor in an 365bet体育投注_365bet体育娱乐场-app官方下载@ System camera evaluates a huge volume of movement data from both the image sensor and the gyro sensors built into the lens, combining this data for even more accurate IS, and because the IS system in the lenses is getting the data that bit quicker, it can compensate for different levels of shake more quickly as well."

Both the RF 400mm F2.8L IS USM and RF 600mm F4L IS USM deliver outstanding image quality, with exceptional performance across the frame. This is thanks, in part, to the two lenses incorporating four types of special optical elements, including fluorite glass and Air Sphere Coating (ASC) technology.

"Fluorite is the perfect material for optics, but it's also the most expensive," explains Mike. "However, it does mean you can reduce the glass elements, making the lens lighter while maintaining the optical quality.

"ASC is an advanced coating that can be applied to lens elements with a large curvature to reduce reflections," he continues. "Light travels at a set speed. When it hits glass, it changes speed, and that's what causes refraction. The ASC slows the light down, so when it hits the hard surface of the glass any flare and refraction is massively reduced."

Both the RF 400mm F2.8L IS USM and RF 600mm F4L IS USM are built to Canon's exacting L-series standards in order to withstand the rigours of professional use. Not only that, but because the lenses are the lightest in their class, they offer huge benefits for photographers who use them regularly.

"The people using this type of lens tend not to be fair-weather photographers," explains Mike. "They are shooting in the cold, in high temperatures, when it's very wet or very dry. These lenses are designed to work everywhere, from the Antarctic to the Sahara."

One issue that can affect objects such as large telephoto primes when they are exposed to high temperatures is thermal expansion and contraction. "Basically, the lens moves a little – just a few microns, but that's like shifting your focus," explains Mike. "Because we made the lenses lighter, we had to improve the thermal efficiency because there is less mass to absorb the heat."

To overcome this issue, Canon designed a two-layer barrel structure, used in both lenses, to reduce the chance of heat being passed through to the inner elements. In addition, the lenses also feature a new type of thermal coating. "It might just look like white paint, but there is a lot of technology within it," says Mike. "It's a heat-resistant paint that reflects UV light to reduce the temperature of the lens."

Because Canon has been working with some of the best professional photographers for decades, it also knows exactly what they want and need. Take for example the lens hood. Both the RF 400mm F2.8L IS USM and RF 600mm F4L IS USM come with a large lens hood supplied, but an optional smaller lens hood is also available. "Football photographers aren't allowed to have their lenses protrude in front of electronic hoardings," explains Mike. "If you have a long hood, that means you're slightly further back, and you want to be as close to that hoarding as possible. Taking the hood off is one option, but if it rains or there's a lot of sunshine, a smaller lens hood is a must."

In addition to being able to use the latest Extender RF 1.4x and Extender RF 2x with both the RF 400mm F2.8L IS USM and RF 600mm F4L IS USM, the lenses also feature an RF aperture mechanism that can be adjusted in 1/8-stop increments, meaning they are just at home shooting video as they are stills. "The smaller increments when changing aperture are much more precise," explains Mike. "That means you won't notice the transition when shooting video."

Unlike other RF lenses, though, the RF 400mm F2.8L IS USM and RF 600mm F4L IS USM don't feature a dedicated control ring – but there's a good reason for that. "When you're holding a big lens, having a ring at the back wouldn't make sense as you want your hand to stay at the front," explains Mike. "That's why the focusing ring can double as a control ring. It's a more logical place for your hand to sit when using these lenses."