“Turning the focus ring while looking into the rear part (mount part) of the lens moves the rear lens group back and forth. It seems to moving the lens group with a large number of lens components instead of the inner focus type and the rear focus type that move one to two small lenses as a group.
I asked implicitly to the development member of the lens, “Details are not yet able to talk, has adopted the true/proportional focusing system that does not destabilize the balance of the optical system.”
To say that … ‘s below is my imagination, I guess you are adopting the rear group focus method.
In many ways to a fixed group summarized in group by moving it back and forth focusing lens, benefits of the group focusing method after this becomes more noticeable in a short-distance aberrations and the angle of view changes due to the focus position (breathing ) Can be relatively easily reduced. Unlike a front group / total group focusing method, there is also an advantage that the entire lens length does not change with focusing.
Conversely, as a disadvantage, the focus lens group becomes heavy and heavy, making speedy AF distance measurement difficult. Therefore, high-speed AF is possible (generally, though) even with a non-powerful motor in the inner focus type and the rear focus type of a compact and lightweight focus lens group.
However with a lens like ★ 50mm, to move heavy focus rear group forward and backward at high speed AF, a drive motor with power (torque force) is needed. If it is an MF lens, do not worry about it at all.
★ 50mm F1.4’ s adopted AF drive motor is a SDM (Supersonic Direct-Drive Motor) as also mentioned in the lens name.
According to the press release “to realize the excellent AF to quietness at high speed, equipped with a newly developed ring-shaped SDM (ultrasonic motor)”.
According to Ricoh’s newly developed arc-type ultrasonic motor, (according to the development team member,) “It is SDM which was newly designed and developed with emphasis on power”.
The ring type SDM with PENTAX lens is already used in D FA 15-30 mm F 2.8 and D FA 24-70 mm F 2.8. Well, there will be some “nasty people” who will have doubts as there is no difference between those SDM systems; but there is something like that, gentleman. It may be acceptable to convince that “Ring-type SDM newly developed focusing on power”. What can be clearly said is completely “different thing” than the existing ring SDM and the SDM.
Even if you look at the OVF while making a phase detection AF, or even if you do an image plane AF in live view, it will be in focus fairly quickly and silently.
Although it is not “comparable” compared to the combination of the other companies’ the state-of-the-art camera and the lens can not afford the “equivalent”, it was almost without feeling the stress of distance measurement speed. Since it is a beta lens, the accuracy of AF speed still remains unknown. The algorithms of the AF control will be adjusted in the near the future. The operation feeling of the focus ring in the MF mode is good. It was not heavy, it was not light, it was a smooth and sure feel.
Photographing with phase detection AF by looking in the optical viewfinder is recommended to focus on the center-point in the frame, especially if it becomes F1.4 large aperture like this 50 mm lens.
However, if the lens with a large aperture 50 mm class, the angle of view makes the phenomenon of cosine error conspicuous, it will be difficult to master it (it will be much easier to use if it becomes 85 mm class). That does not mean I can not recommend it because I choose the peripheral AF frame around the edge (from me) – Because it differs depending on the model, it can not be said unconditionally, but devises shooting with a PENTAX camera. It is recommended that you shoot with AF at the center-point while shooting.
Thus slightly larger as certainly 50mm F1.4 lens also try to hand. Besides, it’s heavily heavy. However, if you focus exactly and take a picture, this really looks really good. I thought that “whether it is a little big or heavy, it is still OK for such kind of lens.”
to be continued…”
(text translated from Japanese)
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