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[Part 2] Story of PowerShot G1 X Mark II – Lens & barrel


Part 2 of the PowerShot G1 X Mark II Developer's Interview will feature "Lens". We will review in detail the refined optical performance of the lens employed in PowerShot G1 X Mark II - the flagship model of the PowerShot G series which is packed with Canon's latest cutting-edge technology. In this series of articles, the Developers of this model will share with us the challenges that they faced when developing this model.

Pages: 1 2

(from left)
Norihiro Nanba, Image Communications Products Operations, ICP Development Center 1, Staff Engineer / Shuichi Mogi, Image Communications Products Operations, ICP Development Center 1 / Tomoyuki Kudo, Image Communications Products Operations,ICP Development Center 3, Senior Engineer

Innovative challenge toward a new dimension

― Wider viewing angle, zoom magnification, and f/number. Optical specs have been improved in this model. How were you able to achieve these while maintaining the compact body size?

Mogi The G1 X Mark II uses a six lens group construction, the most for a Canon compact camera. The G1 X had a four lens group construction, so there is more freedom for the lens distribution, and significantly greater variation of design. By drawing out the best of everything from the shape, glass material, distribution, to the coating for each of the 14 elements, an all around improvement in specs was achieved.

Nanba On the other hand, by adding just one more lens group, there is a market increase in the precision required for lens position control, and the level of difficulty for manufacturing. This is the reason why a six group construction was not used until now. However, there is greater freedom of design with six groups, and it has the merit of being able to increase magnification even in a restricted space. Consequently, we spent more time than before testing simulations on the computer, and pursued the actuality of designing a six group construction. Using an unprecedented construction was a major challenge, but in order to achieve flagship performance, made numerous tests, making it possible to eventually arrive at the current construction.

5x Optical Zoom (24-120mm) F2.0(W) -F3.9(T)

Optimized multi-layer membrane coating on all lenses reduces ghosts and aberration.

A: Group 1: Large diameter thin lenses
High-refraction glass materials result in a shorter zoom stroke.
B: Group 5: Inner focus
Although the G1 X used a rear focusing system, the G1 X mark II employs an inner focusing system which contributes to minimal lens movement, faster AF speed, a compact form, and improved macro shooting performance.
C: Three aspheric lenses
Three aspherical lenses, including a UA lens, provide excellent aberration compensation.

― The six lens group construction was a first attempt, with a high level of difficulty, what made it possible to achieve?

Nanba As it is a construction that required sensitivity with a high level of lens control, we had repeated discussions with the lens barrel design division. Also, in order to achieve mass production, development progressed with close coordination with the factory. I believe that this coordination was a major factor in attaining this difficult goal.

Mogi The premium G and S series compact cameras models are manufactured at Nagasaki Canon Inc.,. There were repeated enthusiastic discussions with the same goal in mind and soon, a manufacturing system was established for the G1 X Mark II's lens.

Kudo Looking at it from the aspect of the lens barrel, the mechanical parts does a good job of controlling the high level of sensitivity. As the existing methods were not able to achieve the required precision, making these adjustments was an extremely difficult job. In cooperation with the algorithm development division, we were able to achieve lens control by adopting an original method. In addition, new manufacturing methods at the factory were also necessary. In order to achieve high precision, manufacturing the G1 X Mark II's lens barrel required many more processes than before; however, with the introduction of new equipment, etc., mass production that maintains precision on a micron order was achieved.

The six lens group
(Above, from left): Group 1/ Group 2/ Group 3
(Bottom, from left): Group 4/ Group 5/ Group 6

― The G1 X Mark II is equipped with a large-diameter lens, but does it take advantage of EF lens knowhow?

Nanba Many of Canon's optic divisions are concentrated in Utsunomiya. As optic designers for not only the SLR division, but some others such as semiconductor exposure equipment, and broadcast equipment are gathered together, it is an environment where synergistic results can occur easily. It is a place where the exchange of information occurs regularly, where it is possible to always have a mutual exchange of information, and you can see what kinds of design different divisions are doing. The EF lens division in particular works in the same field of cameras, so closely handling information is a real strength.

Mogi In fact, the technology for EF lenses and EOS M interchangeable lenses gave us major leads for the development this time. Also, in the past, I handled the design of optics for consumer video cameras. Almost all video cameras for home use have bright, large-aperture lenses of f/1.8, etc. This experience and knowledge was useful during the design of the large-diameter lens this time.

― A lens barrier that was not included on the G1 X has also been included.

Kudo As there were strong demands from G1 X users for this, we looked into the possibility of a lens barrier from the start of development.
However, by attempting to completely store a barrier that will cover a large-diameter front lens, there was the issue of the lens barrel’s outer diameter inevitably increasing. At this point, we took advantage of technology developed for the PowerShot G15. By making the barrier’s opening with a smaller construction, it is possible to reduce the space for storing the blades, and this means the outer diameter can also be reduced. On the G1 X Mark II, in addition to this, by increasing the number of blades an original 8-bladed barrier was developed that made it possible to reduce the size of the opening, thus we were able to maintain the feel of a compact size while equipping it with a lens barrier.

― The minimum focusing distance during macro shooting was significantly reduced!

Mogi The minimum focusing distance is a concern that we have had many feedback on, so we had in-depth discussions on how we could improve this. In order to shorten the minimum focusing distance, it was necessary to reduce the amount the focus group moves. At this point we had the idea of changing the existing rear focus method, to the inner focus method.

Nanba As the sensor gets bigger, the lens located at the very back will become larger in order to bring in light consistent with that size. For that reason, with the rear focus method the lens group at the back is moved as the focus group. This is effective with a small sensor, but it is not necessarily effective with a large sensor. This is because as the lens becomes larger and heavier, lens drive and control becomes more difficult. In this sense, on the G1 X Mark II equipped with a large format sensor, using the inner focus method which can move an even smaller lens group is extremely effective.

Kudo In order to suppress the irregularity in performance at each focal length, movement of the lens group is firmly controlled in the lens barrel, and it is adjusted so it is possible to shoot beautifully from distant views up to close range. Additionally, as it is possible to suppress the amount of distance the focus group moves with inner focus, it was possible to significantly speed up the autofocus.

― Is it true that you pursued how the view looks through the viewfinder with an EVF?

Mogi The external electronic viewfinder was a challenge as it was the first for a Canon compact camera. From the initial design stage, with repeated trial and error, it was developed with Canon's technology. With it, we also enthusiastically designed this EVF with the goal of being the world's best.

Nanba EOS optical viewfinder technology in particular was referred to significantly when it was designed. Particular emphasis was placed on the angle of view, and how good viewing appears. Adjustments were made repeatedly for the number of lenses, construction, and the dioptric adjustment mechanism.

― Can we look forward to beautiful background blurring like that of SLR cameras?

Mogi Beautiful background blurring that is only found on large format sensors was the part of development with the most emphasis. Various experiments were repeatedly carried out for this from the earliest stage of development, along with repeated discussions about making it a wider diameter. As a result, f/numbers of f/2.0 (W) - f/3.9 (T) are achieved taking advantage of the G1 X Mark II's 1.5 type * large format sensor as much as possible.
*Total pixels : Approx. 15.0 Megapixels Effective pixels : Approx. 12.8 Megapixels(3:2)

Kudo A 9-blade aperture diaphragm is included to achieve beautiful background blurring. This makes it possible to beautifully express round blurring that is almost circular. Also, by using nine blades, as each blade is smaller, the outer diameter size of the lens barrel is successfully restrained.

The amount of aperture opening according to f-number. From left, f/2.8, f/5.6, and f/11.

― What merits does the G1 X Mark II camera have for users?

Mogi Even though the G1 X Mark II has a large format 1.5 type sensor*, high product specifications such as the focal length, f/number and minimum focusing distance improvements were achieved on this camera. To provide for a large range of shooting situations, for example portraits with really blurry backgrounds are possible with the aperture wide open, and when stopped down it is possible to shoot clear photos when you want it to be in. As it is possible to shoot great photos from close up to far away, I would like to see people shoot all kinds of variations, and enjoy finding their own best shot.

Kudo As we received feedback from the market regarding the macro shooting distance on the G1 X, I think that it is a major achieveachievement for us to reduce the minimum focusing distance 5 cm on the G1 X Mark II. With it, better macro photography for flowers and food, is now possible.

Nanba We did not just go after specs with the G1 X Mark II, it was developed with the goal of a camera with high power of expression that can be enjoyed on a daily basis. As a result, I believe that the optimum balance between size and performance was achieved. As a variety of photo styles in a wide range of scenes are possible with this camera, I would be happy if people took the kind of photos that could be entered in photo contests.

PowerShot G1 X Mark II

Lens max. aperture: f/2.0 (W) - f/3.9 (T)
Lens focal length: 24mm (W) - 120mm (T)*1
Min. focusing distance: 5cm
Image sensor type: 1.5" COMS sensor *2
Image processor: DIGIC 6

*1 35 mm film equivalent
*2 Total pixels : Approx. 15.0 Megapixels, effective pixels : Approx. 12.8 Megapixels(3:2)

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