| inviato il 28 Luglio 2016 ore 18:42
Come da oggetto, segnalo la seguente intervista, riguardo al sensore e sistema di messa a fuoco.
snapshot.canon-asia.com/article/en/interview-with-developers-eos-1d-x-
Riguardo al sistema di messa a fuoco, segnalo i punti salienti:
"The AF area is slightly vertically longer than before, but the number of AF points and their layout pattern basically remain unchanged compared to the EOS-1D X, am I right? Recent APS-C size DSLR and mirrorless cameras offer a wide AF area that covers up to the edges of the image. If I could ask for more, I would have liked a larger AF area on the EOS-1D X Mark II.
Is it technically difficult to widen the AF area any further on a full-frame DSLR camera?
Sakaguchi: We made every effort to broaden the sensor surface, and were able to expand the AF area vertically as a result. It would be extremely difficult to widen it any further without increasing the size of the camera.
The Intelligent Viewfinder II on the EOS-1D X Mark II allows users to view the shooting information. The area covered by the AF points is vertically longer than that of its predecessors.
Seita: Our team in charge of AF asked us if it was possible to upsize the secondary mirror slightly, but there was no space for us to do so. This was why we tried to broaden the AF area as much as possible by using the light beams from all the way to the edges of the secondary mirror.
"
"What were the key reasons that enable all the 61 AF points on the EOS-1D X Mark II to support AF at the maximum aperture of f/8?
Sakaguchi: Many of our customers requested for compatibility with AF at f/8, but what we could offer on the EOS-1D X was limited. This was why we have been working on this point since the day we embarked on the development of the EOS-1D X Mark II.
By expanding the camera and lens systems to allow light at f/8 to be utilised to the fullest, we were able to achieve AF at f/8 with a sufficient level of focusing accuracy.
However, as lenses have different characteristics, there may be some lens pairings that don't support the use of AF points in the outermost circumference, or where not all 61 AF points are usable.
Masamura: For the latest lenses such as the EF600mm f/4L IS II USM, EF500mm f/4L IS II USM and EF100-400mm f/4.5-5.6L IS II USM, all 61 AF points are usable, even when you pair them with an extender, which results in a maximum aperture of f/8. However, you will have to use an extender from Series III."
"- The AF point at the centre supports a low light limit of up to EV-3. What about that for the peripheral AF points?
Sakaguchi: The low light limit of EV-3 is applicable to the centre AF point when the camera is used with a bright lens that is at least f/2.8. Comparatively, the low light limit of the peripheral AF points would have a low light limit that is approximately 1 to 2.5 stops higher.
- What is the reason for the improvement in the low light sensitivity performance of the camera? Is it because of the enhanced sensitivity of the new-generation AF sensor?
Sakaguchi: Yes, one of the reasons is the enhanced sensitivity of the AF sensor. Besides that, the key factor that affects AF under a low light condition is noise, so we came out with a new AF sensor that is capable of reducing noise by a large extent.
- The latest version of AI Servo AF is “III+”. What does the “+” sign mean?
Sakaguchi: AI Servo AF III performed extremely well when tracking subjects that are moving constantly toward or away from the camera. However, tracking may slow down in some cases when the moving subject changes its speed or direction suddenly.
To address such sudden changes in speed and direction of the subject, we have boosted the subject tracking performance during predictive AF with AI Servo AF III+. For example, the predictive AF algorithm has been improved to enable a speedier response to abrupt changes in the speed and direction in a scene such as motor sports cornering, where a fast-moving subject approaches a corner, changes its direction of movement and moves away from the camera at a high speed"
Riguardo al sensore, invece (curiosamente non menzionano la gamma dinamica):
"- In order to achieve a continuous shooting speed of approximately 14 fps, were there any other important design considerations besides those for mirror drive and the AF system?
Seita: The image sensor and image processor would heat up more easily taking into account the camera's compatibility with the 4K/60p resolution and the higher continuous shooting speed, so we introduced thorough measures to discharge heat efficiently.
As illustrated in our product catalogue, we installed a heat pipe on the board to which the image processor is mounted so that heat is discharged to the aluminium alloy at the roof of the battery compartment. In addition to the heat pipe, we also included lead wires for heat from inside the metallic body to escape. Such thoroughgoing measures to prevent heating are not found on the EOS-1D X.
We have positioned the image processor right behind the image sensor to achieve a high readout speed. As both these components contribute to heating, we installed a heat pipe to form a structure that enables heat to be discharged efficiently from different parts of the body.
- That's very similar to the structure around a high-spec PC motherboard or graphics card. By the way, there is a question which I missed out at the beginning of the interview: how did you arrive at a resolution of approximately 20.2 megapixels for the EOS-1D X Mark II?
Okado: We took into consideration the balance among the pixel count (resolution), ISO speed and frame rate. Raising the pixel count excessively makes it difficult to increase the frame rate as the signal readout speed would slow down as a result. The pixel size would also be smaller, which also makes it more difficult to enhance the ISO speed.
- The resolution of the EOS-1D X was approximately 18.0 megapixels. To me, the increase to 20.2 megapixels on the EOS-1D X Mark II is very small.
Masamura: There may be some who feel that we might as well keep the pixel count unchanged, but there are also users who wanted a higher pixel count. In order to satisfy the needs of as many users as possible as a flagship model, we believe there is significance in enhancing the resolution, no matter how small the increment might be.
- Was compatibility with 4K/60p movies a consideration? In other words, was 20.2 megapixels the optimal pixel count for processing 4K/60p movies?
Okado: No, the resolution has nothing to do with 4K movies.
- In the past, whenever a new-generation image sensor or image processor is introduced, the maximum ISO speed for normal use would be raised at least by about one stop even when there is an increase in the pixel count. It was therefore surprising to find that the maximum ISO speed of the EOS-1D X Mark II remained unchanged at ISO 51200 compared to its predecessor.
Hattori: A higher pixel count would, in principle, cause more noise. To address the noise issue, we tried to make improvements to the sensor's structure and employed the latest image processor for sophisticated image processing to ensure that ISO 51200 remains usable as the maximum normal ISO speed.
Indeed, it would be ideal if we could raise the ISO speed to one stop higher, but we were still unable to achieve that level. However, if you take a test shot at the same ISO speed using both the EOS-1D X and EOS-1D X Mark II, you would find that chromatic noise is less noticeable on the EOS-1D X Mark II at a high ISO speed setting."
per dettagli sulle altre funzionalità, incluse quelle video, rimando al seguente articolo:
snapshot.canon-asia.com/article/en/eos-1d-x-mark-ii-review-of-function |
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