With the release of the EOS 5DS and EOS 5DS R just around the corner, I have conducted an interview with the development team to understand more about the new technologies introduced on this 50-megapixel ultra-high-resolution camera as well as the challenges involved in its development. (Reported by Ryosuke Takahashi / Photos of interviewees by Takehiro Kato)

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Long-awaited ultra-high resolution

- First of all, can you tell us more about the development concept of the EOS 5DS and EOS 5DS R?

Tachibana Both models were developed based on the EOS 5D Mark III for users who are seeking high-resolution photos. The EOS 5D Mark III is a very popular and well-balanced camera, but we have received feedback saying that the pixel count was not good enough. In terms of pixel count, we cannot deny that we were one step behind our competitors. Canon's focus for the past EOS models was to improve the total performance while ensuring their ease of use including high sensitivity characteristics, rather than just pursuing a high pixel count. However, in response to the large number of requests for a higher pixel count from both local and overseas users, we decided to launch these two models in the market.

- Can you describe more on the aim and intention on the naming of the models?

Tachibana Rather than seeing these cameras as being evolved from the EOS 5D Mark III, it is better to position them as being derived from the EOS 5D family, which focuses on pixel count and apparent resolution. This is why we did not name them as "Mark *", which is adopted for models that have undergone classical evolution. The origin of the "S" naming is the same as that for the EOS-1Ds, which was released in 2012 as a model with higher image quality compared to the higher-speed EOS-1D. In addition to this, a low-pass filter cancellation effect model is also available, and the differences between the two models are emphasised with the letter "R", which stands for "Resolution", added to the end of the name.

- So now there are five models in the full-frame EOS lineup. Please tell us how the new models are positioned and the division of roles among them.

Tachibana Each has their own characteristics, but the most well-balanced model would be the EOS 5D Mark III. The EOS-1D X focuses on high speed, durability, and high sensitivity, while the strongest appeal of the EOS 6D lies in its light weight and compact size. In comparison, the EOS 5DS models open up a new frontier in terms of pixel count and resolution. In the past, "widening the scope of photographic expression" has always been the aim whenever Canon introduces a new product. By filling in the only missing piece, which is pixel count and resolution, we are now able to offer a more complete line-up for our full-frame EOS cameras.

- What are the target subjects respectively for the EOS 5DS and EOS 5 DS R?

Tachibana Both the EOS 5DS and EOS 5DS R offer a sufficiently high level of resolution, so the difference between them in this respect is negligible. Based on this consideration, the main subjects for both models are landscapes and nature. However, the EOS 5DS and EOS 5DS R vary in the availability of a low-pass filter effect, and I could also tell the difference in the results they produce. The purpose of a low-pass filter is to reduce false colour and moiré, and we believe that it is an essential item. It is generally known that false colour and moiré are likely to occur in areas such as the wall surface of a building and the texture of a fabric. In fact, if we look more closely at the photo data released on Canon's official Japanese website (an example is below), we would find moiré present in a part of the subject captured by the EOS 5DS R. Report was received from the development team on the occurrence of moiré, but we decided to show the photo on the website to illustrate the importance of the low-pass filter to our users. That being said, the level of false colour or moiré observed is extremely low, and we hope this information can come in handy when a user is unsure which model to choose.

EF16-35mm F4L IS USM / Aperture-priority AE ( 1/500sec., f/11 ) / ISO 200 / WB: Auto / Picture Style : Fine Detail

Excellent performance in handheld photography

- Now I have a better idea about their resolving power. By the way, can I also use these two models for handheld shots and snapshots?

Tachibana Yes, basically you can take handheld shots with these cameras. However, as they have a higher pixel count than other models, camera shake may occur more easily. While the acceptable amount of blurriness also varies with each user, it is better to select a faster shutter speed than before if you are taking a handheld shot, and it would be more reassuring to make use of a tripod. When we first started on the development of the 5DS models, my very first request to the development team was "to adopt a design that prevents shake from occurring within the camera". For camera shake, users are able to exercise caution, such as using a faster shutter speed, or a lens equipped with the IS feature. However, shake occurring from within the camera can only be addressed by the manufacturers. We have implemented thorough measures to tackle this issue, but we leave it to our users to decide whether the image quality of the handheld shots is good enough for them. For example, the aerial shot published in our catalogue in Japan was taken from a helicopter. Of course, the skill level of the photographer is also a factor, but nonetheless it shows us that these models are capable of producing high-quality handheld photos.

- In other words, we need not rely totally on a tripod.

Tachibana That's correct. A camera that can be used only with a tripod cannot be called an EOS. We do not manufacture medium format cameras.

- What about the internal structure of the EOS 5DS and EOS 5DS R? Are they identical except for the availability of a low-pass filter cancellation feature?

Tachibana Yes, besides the low-pass filter cancellation feature, they are exactly the same. The other differences would probably be the name on the emblem and the strap (laugh).

- The price for the EOS 5DS R is slightly higher. Why is this so?

Urakami In terms of concept, the EOS 5DS R is like a custom-built model. As special components are introduced to cancel the low-pass filter effect, these are reflected in the pricing of the camera.

Tachibana We have always adopted a low-pass filter on the past EOS SLR cameras. The EOS 5DS R is the first model to come with a low-pass filter cancellation feature, but we have no intention to develop a model without a low-pass filter, hence our decision to offer a conventional type and a cancellation type.

- When choosing a lens, what are the points that users need to bear in mind?

Tachibana It will be possible to enjoy a sufficiently high level of apparent resolution using the EF lenses that our users are already in possession of. However, from the camera's perspective, it is a fact that attaching a lens with a higher resolving power would help to produce better results. That being said, this is something that applies not only to the EOS 5DS and EOS 5DS R, but all other cameras as well.

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Dramatically enhanced processing performance

- In what ways are the features and performance enhanced by the use of dual DIGIC 6 image processors?

Uchida The basic performance is enhanced with the upgrade to dual DIGIC 6. The maximum continuous shooting speed is about 5 fps, but the data size during continuous shooting would be huge considering the resolution of about 50 megapixels. This spec would not be achievable without DIGIC 6. In addition to the image processor, the processing performance of the overall system design, including the front-end processing circuit, has also been improved as a result.

- Is there any reason behind the common number "5" for the 50-megapixel resolution and the continuous shooting speed of 5 fps? Was it intentional?

Tachibana Yes, and not forgetting this is a "5"D model (laugh). Jokes aside, the top management of the division was very particular about the continuous shooting speed. At the beginning, the maximum limit was said to be about 4 fps according to the development team, but the management thought this was too low and carried out repeated negotiations before achieving the current spec.

Uchida It was a tough process. I was on the verge of giving up on several occasions (laugh). It would not be possible to achieve this spec unless we made fundamental changes to the aspects that caused the bottleneck in the processing speed. Although it was not necessary to redesign the firmware from scratch, we did make considerable revisions. Also, with the higher resolution of about 50 megapixels, the pixel pitch is narrower than that of the EOS 5D Mark III. The ability to maintain the ISO speed at a certain level under such conditions can also be attributed to the excellent performance of the image processor.

- Can you tell me more about the enhancements made on the new image sensor, including how you were able to achieve a resolution of about 50 megapixels?

Uchida It was our first time trying to build a full-frame image sensor with about 50 megapixels. Of course, the pixel pitch would be narrower, so we started with a new miniaturisation process to gather more light, thereby widening the light path. Besides gapless micro lenses, high-performance photodiodes have also been employed to convert light to electrical signals efficiently. The latest technologies have also been introduced on the transistors inside the pixels. These are the technologies for gathering light and securing the signals. 16-channel readout is then used in order to transfer the huge amount of data for the 50-megapixel resolution at a speed of about 5 fps. The data is in turn received by four A/D conversion front-end processing circuit, and transferred from the digital front-end processing circuit to the dual DIGIC 6.

- The pixel count is more than double that of the EOS 5D Mark III. What were the technological breakthroughs that made this possible?

Uchida One of them is the number of readout channels. We increased the number of channels for data readout to 16, followed by consolidating the data at a single digital front-end processing circuit before distributing it to the two DIGIC processors. We have gathered all our knowledge on how the huge amount of data can be transferred at a high speed.

- So there is only one digital front-end processing circuit. Wouldn't it be possible to increase the speed if parallel processing were performed by multiple digital front-end processing circuits?

Uchida Of course that would be an option too. However, increasing the number of chips would add cost and weight to the camera. Not only so, the biggest challenge is the electrical power, as movie recording, for example, would consume a lot of electricity and cause heating. So our point was to achieve a higher speed without increasing power consumption.

- Is 16-channel readout drastically different from that by eight channels?

Uchida It is like water from small streams converging into a large river. The key point of this technology lies in how data is allocated. While 16-channel readout is not difficult to achieve in terms of hardware, it is important to consider how power consumption can be minimised while allocating the signals efficiently. Canon's unique technologies are also utilised to enable high-speed readout while reducing noise.

- How different is the depictive power compared to the class of cameras with about 20 megapixels?

Shirai We took test shots during the developmental phase while making comparison with the EOS 5D Mark III, and found out that the EOS 5DS series is capable of producing images with dimensionality. The difference between the 20-megapixel and the 50-megapixel models can be observed in all scenes. For example, areas that appear crushed in the image captured by the EOS 5D Mark III are clearly reproduced in the image by the EOS 5D series. Personally, I feel that it is through the accumulation of such minute details that contributed to the dimensionality in the expression.

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The much-talked-about low-pass filter cancellation feature

- Can you explain how the low-pass filter cancellation feature cancels the low-pass filter effect?

Urakami The function of the low-pass filter is to minimise the occurrence of false colour and moiré by reducing the resolving power of high-frequency waves. As with other models, the EOS 5DS comes equipped with a low-pass filter. However, the effect of the filter is weakened compared to other cameras to obtain a high resolving power that is appropriate for the pixel count. Although the EOS 5DS R adopts the same principle as other models to divide a beam of light into two components, the two components are merged back into one to achieve the same effect when a low-pass filter is not used. The process of merging two light components into one is done by making use of birefringence based on the anisotropic properties of crystals and cutting out a crystal in the crystal direction where two point images merge back into one. While there is an extremely slight amount of error, the rate of restoration is almost 100%.

Cross-sectional Diagram of Low-pass Filter

The structural difference between the low-pass filter of the EOS 5DS and that of the EOS 5DS R lies in the presence of a phase plate at the back of the infrared absorption glass. At the same time, the roles of low-pass filter 1 and low-pass filter 2 vary too. Light is not split further in the case of the EOS 5DS R. The split light is combined instead.

- Besides the restoration process being carried out by low-pass filter 2, is the structure of the EOS 5DS R the same as other models?

Urakami Strictly speaking, they are slightly different. While conventional low-pass filter 1 splits the subject in the horizontal direction, it is employed to split the subject in the vertical direction on the EOS 5DS R. Light split by birefringence of the crystal can be divided into ordinary ray and extraordinary ray. If light that enters the crystal linearly is regarded as ordinary ray, then extraordinary ray will be light that is split in both the vertical or horizontal direction depending on the crystal orientation. On the EOS 5DS R, the restoration process can be thought of as extraordinary ray being overlapped with ordinary ray using the birefringence of crystals cut out in the appropriate crystal direction.

- Now I have a general idea of the principle, but why is it possible to restore the extraordinary ray?

Urakami Crystal is used for the low-pass filter, and birefringence is made use of to reintegrate the light rays. As I have explained earlier, ordinary and extraordinary rays are split according to the crystal direction. By adjusting this orientation, it is possible to divide a point image into two or combine two into one.

Conceptual Diagram of Low-pass Filter

The low-pass filter on the EOS 5DS splits a point light into the horizontal and vertical directions, while at the same time shifts the phase by polarising light circularly with a phase plate. The point light is eventually split into four points on the sensor and the high-frequency level removed, thus allowing the high-resolution models to prevent false colour and moiré.