Will the ZK Series Revolutionize Advertising Photography?

When Fujinon developed the ZK Series, the goal was to create a zoom lens with optical performance on a par with that of a prime lens. To see whether this ambitious goal was achieved, Tokyo video production group Ellroy Inc. carried out a thorough hands-on investigation. The pros at Ellroy use single-focus prime lenses on a daily basis and have extensive experience of shooting video and still images at 4K and even 6K resolution. They looked to tackle a common perception among creators in the advertising industry: the idea that zoom lenses, for all their undoubted functionality, can fall short when it comes to image quality. Would the ZK Series be able to flip that notion on its head?

First up in the test was a pattern corresponding to a T-number of 2.9. If you look at the center chart, the image resolution of the PL-mount prime lens is indistinguishable from that of the ZK Series lens. What’s more, when you consider the sharpness of the bold lines and text on the periphery of the chart (i.e., in the four corners), you could even say that the ZK Series is superior.

For the comparison using a maximum aperture value, it’s easier if you simply look at the chart photographs rather than read an explanation. Even a seasoned pro like Kazumi Takahashi—a photographer who has been staring through a viewfinder for over 10 years—was astonished at the level of resolution.

For a start, the number of lens elements that make up a zoom lens is extremely large compared to a single-focus prime lens. The developers explained that the ZK Series is composed of around 30 lens elements and that correcting distortion for all of these elements is extremely difficult. They noted that a large-diameter aspherical lens served to prevent distortion from occurring. Thanks to its long-term involvement in making broadcast TV lenses, Fujinon has accumulated a wealth of know-how in this area; for example, they successfully mounted the world’s first 30 mm or larger large-diameter aspherical lenses. Fujinon harnessed its technical capabilities and applied them to the development of cine lenses. They fine-tuned the composition ratio of low-dispersion glass and high-refractive index glass—two materials with different light dispersion properties. This intense dedication to the task resulted not only in low distortion, but also in high levels of contrast and 4K resolution.

As we saw above, ZK Series lenses incorporate about 30 lens elements. The Fujinon developers say that each lens element was fabricated after first reviewing the glass materials from which the element is made. The aim was, of course, to achieve the quality of a single-focus prime lens. Fujinon experimented with all sorts of combinations of glass materials, and further, with special coatings on filters, and the like. They continuously modified technologies for adjusting contrast and eliminating flare. Thanks to their painstaking efforts, the resulting image quality and finish is uniform across the four models of the ZK Series. The same goes for the HK Series, Fujinon’s lineup of high-end cine zoom lenses, and the Alura Series of cine lenses jointly developed with the ARRI Group. The ease of color grading is another area where these lenses will receive acclaim.

Fujinon's commitment to quality can be seen in the nine-blade aperture diaphragm the company introduced in the ZK Series. This design emerged from a wide range of simulations of aperture configurations. It captures light in a beautiful circular shape in all scenes, whether the aperture is at its widest or narrowest setting. And when it comes to crepuscular rays (“sun rays”), the nine-blade diaphragm draws out beautiful rays without excessive glare. Of course, full 4K support is possible with a compatible sensor size of Super 35 or greater. The ZK Series makes sense as a family of lenses that enable rich image expression that goes beyond the scope of existing zoom lenses.