- Next, I'd like to ask you about the lens. How is it different from the one for the DP2 Merrill?
[ Mr. Kono ]
It has the same construction, but has a larger barrel because of the built-in AF lamp and motor, as well as the design balance.
- When was the lens designed and what are the bottom lines in the design?
[ Mr. Kono ]
We started designing it about three years ago. Our primary goal was to make a lens that withstands the DP2 Merrill's sensor which requires resolution higher than 100 line-pairs per millimeter. So, we made great efforts to meet the requirement as much as possible to the corners.
[ Mr. Yamaki ]
We calculated the resolution limit using the lens design data, and found that it still works with the Quattro without problems. So, we decided to continue to use it.
- Could you explain the lens construction?
[ Mr. Kono ]
It has a diaphragm in front of the lens. The front group including the diaphragm does focusing. This construction is a sort of Double Gauss permutation in that it's a Double Gauss without the front side. To shorten the length, the back group has a tele-converter. This also extends the focal length while improves the telecentricity (the incident angle to the sensor). This kind of construction is common among fast lenses with smaller maximum apertures, but we stopped down to improve corner depiction. It's a luxurious lens. It's impossible to directly divert this lens to an interchangeable lens, but we used the same concept for the mirrorless 30mm F2.8.
- I see. Sounds like a very luxurious lens. What are your thoughts on controlling bokeh?
[ Mr. Kono ]
We simulate bokeh as much as possible, but first, we pursue higher performance. The position of a diaphragm has a strong impact on vignetting. Also, we under-correct the spherical aberration slightly (pull the focal point slightly). This way, we have to sacrifice resolution, but instead, we can get more beautiful back bokeh.
Mr. Tomoki Yukino, Vice Chief of the 2nd Unit, Design and Developing Department.
Even though I went too far by asking him to release the very unique lens, he evaded the topic with a smile. Sorry about that!
Because I often see lens constructions of SLR lenses, I find the one of compact cameras truly interesting because so many measures are taken to achieve both compactization and high image quality. The lens for the DP2 Merrill and the dp2 Quattro produces beautiful back bokeh. I'm repeating what Mr. Kono said, but I think it was developed by pinpointing the balance between the bokeh and the resolution. It may be effectively impossible to correct spherical aberration perfectly. But, practically, there're less scenes that we experience beautiful front bokeh. So, I understand why they give weight to back bokeh.
