EOS 5D Mark IV Interview with Developers (Part 2): DIGIC 6+ and the 30.4MP Resolution
The new EOS 5D Mark IV has finally made its appearance. What’s the background to the significant increase in pixel count to approximately 30.4 megapixels? What role does the DIGIC 6+ image processor play? In Part 2 of this interview series, we asked the developers these burning questions. (Interviewer: Ryosuke Takahashi, Group photo: Takehiro Kato)
(Back row, from left)
Kazuki Haraguchi, Megumi Inazumi, Keisuke Kudo, Yasuyuki Watazawa, Takashi Kon, Kiyoshi Tachibana, Yutaka Kojima, Hiroaki Nashizawa
Large improvements to high ISO speed performance while raising the pixel count
- The new EOS 5D Mark IV saw a significant increase in the number of pixels. What are the technologies that made this possible?
Haraguchi: Where the achievement of a Dual Pixel structure with approximately 30.4 megapixels on the EOS 5D Mark IV is concerned, I believe the main contributing factor is the technology that we have established on the EOS 5DS and EOS 5DS R, which come with an approximately 50.6-megapixel image sensor. As you know, increasing the number of pixels means a smaller area per pixel, which would put a heavier burden on the optical features. However, we managed to resolve most of these issues while we were developing the EOS 5DS, and thus were able to concentrate on achieving a high ISO speed performance at the same time, a quality that is essential to the EOS 5D Mark IV as a traditional model of the 5D series.
- I believe the pixel pitch has become smaller with the increase in the number of pixels to approximately 30.4 megapixels. What measures were taken to prevent deterioration of the S/N ratio?
Haraguchi: The pixel pitch of the EOS 5D Mark IV is 5.36μm, which is smaller than the pitch of 6.25μm on the EOS 5D Mark III. Of course, the amount of light absorbed by the sensor decreases the smaller the pixel area sensitive to light. Assuming that the level of noise is constant, the amount of incident light is thus also reduced, which naturally results in a lower S/N (signal-noise) ratio.
To enhance the S/N ratio, we have adopted three measures on the EOS 5D Mark IV. First of all, we reviewed the structure of the photodiodes to secure an area for the photodiode on the pixel more efficiently. Secondly, we improved the transmittance of the colour filters to allow more light to enter the photodiodes. Last but not least, we adopted a new microfabrication process to minimise noise on the sensor.
By combining these technologies, we were able to raise the S/N ratio, which was lowered due to the smaller pixel pitch, to a state that is equivalent to or even higher than before.
- Please explain a little more about this new technology with focus on the transmittance of the colour filter.
Haraguchi: We are unable to disclose the details, but in our efforts to improve the colour filter, one of the approaches we used was to enhance the transmittance so as to raise the proportion of "S" in the S/N ratio.
Let us assume that the amount of light that falls on the micro lenses is 100 units. Out of this, the pixel structure on the EOS 5D Mark III is only able to transmit 80 units. However, with the transmittance of the colour filter improved, the pixel structure of the EOS 5D Mark IV is able to deliver 90 units of the light. Also, we have employed a new material for the colour filter in order to retain its original characteristics. Meanwhile, as for components inside the pixel, other than the photodiodes which are not related to light reception, such as the wiring, we have also changed the layout to boost the basic performance of the CMOS sensor.
- Specifically, which functions would not have been possible without DIGIC 6+?
Nashizawa: For still photography, we would not have been able to achieve noise reduction needed for the maximum ISO speeds of 32000 (native) and 102400 (expanded). Also, diffraction correction during lens aberration correction would not have been possible. Not only so, in addition to processing of the Digital Lens Optimizer inside the camera, processes such as recording in DPRAW have also benefited from the DIGIC 6+. Meanwhile, for movie shooting, some of the functions made possible by DIGIC 6+ would include recording in 4K 25p/30p as well as recording in the high frame rate of HD 100p/119.9fps.
- How is the 150,000-pixel RGB+IR metering sensor on the new EOS 5D Mark IV different from the existing ones such as that on the EOS 5D Mark III?
Kon: What is different from before is the RGB+IR metering sensor’s resolving power of approximately 150,000 pixels—which captures enough information to depict an entire image. The camera detects faces and colours of the subject based on the image captured by the AE sensor. This information is then sent back for metering to enable high-precision control of the exposure. It is this information that makes EOS iTR AF possible.
- What are the functions of the IR pixels?
Kon: IR pixels are sensors that can detect near-infrared light. The data can be used to improve the camera’s ability in judging scenes such as an evening view or morning glow, as well as greenery in a natural landscape shot. They are therefore employed to optimise features such as Auto White Balance, Picture Style Auto and the Auto Lighting Optimizer.
Measures to control heat
- One of the concerns is heating when there is an increase in the throughput of the image processor, including that for AE. How did you resolve this issue?
Kojima: We have taken this issue into consideration since we first embarked on the development of the EOS 5D Mark IV. We repeated different simulations from the early stage of our trial production before arriving at the final design you see now. The most challenging task for the mechanical team was how to handle the heat of the internal components. We devoted a lot of effort to tackle this issue, such as changing some of the external components from resin to metal while paying attention to the robustness of the entire body.
- Could you tell us more specifically how heat is dissipated from inside the camera?
Kojima: The mechanism for dissipating heat is not visible from the external appearance of the camera. Heat tends to be generated particularly around the image processor, so our focus was on how we could direct the heat to somewhere cooler.
- Which part of the camera is the image processor located?
Kojima: The image processor is located somewhere at the back of the Quick Control button, which is rather close to the external casing. The lens mount at the front of the camera body is relatively lower in temperature, so heat is directed there.
- How do you direct heat from the back to the front of the camera? Is it something like the heat pipe of a computer?
Kojima: In a way, it is something close to a heat pipe. What we did to transfer heat from the back to the front was to conduct heat through adhesion or close contact of the different materials by using metals such as carbon and other materials or components that are good conductors of heat. So, instead of dissipating heat with only a single component, we directed heat to the front through the entire internal structure.
Advantages of 4K movies
- Where 4K movie shooting is concerned, what are the advantages of the Movie AF feature on the EOS 5D Mark IV?
Kudo: I would say the advantages are in the AF tracking sensitivity, AF speed, stability and the overall movie quality. These elements are tweaked to allow them to coexist in good balance. Yet another feature of EOS movies is that AF speed and tracking sensitivity can be customised in the menu, so you can adjust the AF speed according to the scene or your photographic intention.
- What is the speed of the moving subject that Servo AF is capable of tracking during movie shooting?
Kudo: It depends on the lens in use as well as distance from the camera to the subject, but in general, it is capable of tracking subjects moving at a speed close to that of a bicycle approaching the camera. Also, the (Face)+Tracking feature can be used to track sideway movements to the left and right, making it possible to apply AF to subjects with movements that are somewhat irregular. (Face)+Tracking is particularly effective for capturing portrait subjects if they are facing the camera.
- The feature for still image capture during movie shooting has been omitted. Please tell us the reason for changing it into a 4K Frame Grab feature.
Tachibana: The biggest reason for discontinuing the still image capture feature is because movie recording would pause for about a second when capturing a still image, and we thought it would not be good to disrupt the flow of the movie shooting process.
- Some users have expressed concern about the still image quality of the 4K Frame Grab feature. Is the resolution of the captured image good enough?
Tachibana: This might vary across individuals, but generally you can think of it as equivalent to the resolution of an 8.8-megapixel still photograph. Besides the image quality, we also find it advantageous to use the 4K Frame Grab feature to extract scenes from movies, as it allows you to capture fleeting moments that would not have been possible via still photography.
Please see the article below for more information on 4K movies.
EOS 5D Mark IV: Movie Shooting Features Include 4K and HDR Recording, Dual Pixel CMOS AF
Column: Experiencing the resolving power of approx. 30.4 megapixels through actual shots
With a significant rise in the pixel count by about 8.1 megapixels from existing models, data size has also increased as a result. When capturing a shot from a far distance, as illustrated in the example below, you can really feel how the higher pixel count has contributed to the stronger resolving power. Also, overall depiction is more precise, with each of the trees clearly defined. In other words, details of the resulting image can be reproduced faithfully with dimensionality.
In principle, since Picture Style standardizes image quality, there is no difference across different camera models. However, in the case of the EOS 5D Mark IV, jagged edges are hardly observed in the outline of the subject even when you enlarge the image on a browser by 200%, so lines would remain well-defined. Besides, since there is allowance in the resolution, effects are prominent when you tweak the sharpness settings, so users can make adjustments according to their preference for a sharper depiction.
Shooting conditions: I attached the EF70-200mm f/2.8L IS II USM to the body of the EOS 5D Mark IV and took a shot of the bay from a distance of about 500m to 1km away. I set the shooting mode to Aperture-priority AE and the aperture to f/8. Also, I fixed the ISO speed at ISO 100, set Picture Style to “Standard”, and Image quality to “JPEG Large”.
EOS 5D Mark IV/ EF70-200mm f/2.8L IS II USM/ FL: 170mm/ Aperture-priority AE (f/8, 1/160 sec., EV -0.3)/ ISO 100/ WB: Auto
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Born in Aichi in 1960, Takahashi started his freelance career in 1987 after working with an advertising photo studio and a publishing house. Photographing for major magazines, he has travelled to many parts of the world from his bases in Japan and China. Takahashi is a member of the Japan Professional Photographers Society (JPS).
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