SONY G MASTER ENGINEERS' INTERVIEW

Sony G Master Engineers' Interview

Sony engineers discuss the concept of the G Master lens, born out of technological innovation and uncompromising optical design.

THE VISION BEHIND G MASTER

"A new brand with a clear vision of the cameras of the future, G Master pursues the ultimate expression of high resolution and bokeh"

Sony Product Planning
Akira Shiraishi

Shiraishi:
Image sensor technology continues to advance, and we believe high resolutions are a universal value that will become increasingly important. Lens bokeh is another universal value, and both will continue to be in demand. In this spirit, with the development of our large-aperture F2.8 zoom and F1.4 prime lenses.

SONY KNOWS THE FUTURE OF IMAGE SENSORS, SO THIS LENS WILL REMAIN RELEVANT IN THE FACE OF CONTINUALLY EVOLVING CAMERA PERFORMANCE

The three products we have developed under the new G Master brand are: the FE 24–70mm F2.8 GM standard zoom lens, which targets prime lens class resolution performance , the FE 85mm F1.4 GM portrait lens, which places a premium on bokeh rendering, and the FE 70–200mm F2.8 GM OSS telephoto zoom lens, which is devoted to capturing powerful resolution in the telephoto end and bokeh in the portrait spectrum.

SUPERIOR ASPHERICAL LENSES

The G Master would not have been possible without this key element
Sony Deputy General Manager - Lens Mechanical Design Department

Masanori Kishi

Kishi:
In developing the G Master, we adopted an XA (extreme aspherical) lens element with a surface accuracy of 0.01 microns. To begin with, aspherical lenses are very difficult to manufacture, and it was a challenge for us to see how far we could raise the surface accuracy.
I think the reason we were able to perfect them to such a high degree was because we were able to use Sony's unique proprietary technology.

Top figure: Conventional lens surface accuracy
Bottom figure: XA lens accuracy (0.01 microns)

HIGH RESOLUTION AND BOKEH: TOGETHER AT LAST

Kishi:
Since high resolution and beautiful bokeh are inherently at odds, it's very difficult to bring them together into their ultimate form. With respect to resolution, we adopted an MTF1 with a spatial frequency of 50 line-pairs per millimeter as our design baseline, the most challenging standard ever.

Ultimately, the goal should be a photo that looks good when you see it, so what matters is achieving a design that's well balanced from the low frequencies to the high frequencies.

Shiraishi:
Within optical design, there are several elements that have an impact on bokeh, but it's difficult to eliminate them completely at the optical design stage. There are bound to be individual differences in the final product, so G Master series lenses are checked one-by-one during the manufacturing process and adjusted to ensure that they produce ideal bokeh before shipment.

INNOVATIVE DRIVE MECHANISM

1. Ring drive SSM
2. Linear motor

RESOLUTION AND BOKEH ARE OPTIMISED BY THE OPTICAL DESIGN, THEN PUT TO THE TEST BY SONY'S ACTUATOR TECHNOLOGY

Kishi:
Even if you establish a balance between high resolution and bokeh and reach the highest levels of performance, you won't get a chance to experience that performance without equal focusing accuracy.

The FE 70–200mm F2.8 GM OSS deals with the weight of the focus lens by splitting the focus group, which is usually one piece, into two separate focus groups. This distributes the weight. Furthermore, by combining the focus groups with independent actuators and controlling them independently, the lens achieves smoother focusing not only for still images, but for video as well. Splitting the focus group also creates a floating structure that makes it possible to effectively correct various aberrations at all subject distances.

INNOVATIVE ACTUATOR TECHNOLOGY ENABLES AN ENTIRLEY DIFFERENT SHOOTING STYLE

In addition, the FE 85mm F1.4 GM and FE 70–200mm F2.8 GM OSS are equipped with new-generation ring drive SSM motor systems that optimises the ring drive SSMs used in A-mount lenses for the contrast AF in mirrorless interchangeable-lens cameras.
The excellent ring drive SSM, dual position detection sensors and an advanced drive algorithm make it possible to control the position of the lens at the 1-micron level, enabling extremely high-precision AF.

A message from Akira Shiraishi
In creating this new 85mm F1.4, I wanted to make it the ultimate lens to surpass all the lenses that came before it. I think that's exactly what we’ve accomplished, and I hope our feelings about the FE 85mm F1.4 GM will be shared by others. And by seriously listening to the feedback from our customers on the F4 series, we were able to improve the performance of our two other lenses in the G Master series, the FE 24-70mm F2.8 GM and the FE 70-200mm F2.8 GM OSS.

A message from Masanori Kishi
We brought these products to market by working out every detail to its logical conclusion, whether in regard to operability, performance or other features, in a way that responds to the input from the users. I believe we've created lenses I can truly recommend with confidence, so it will make me happy to see people actually use these lenses and have fun taking pictures with them. I hope people will enjoy the unprecedented fusion of high resolution and beautiful bokeh that this new G Master series delivers.